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1 | config ARCH | |
2 | string | |
3 | option env="ARCH" | |
4 | ||
5 | config KERNELVERSION | |
6 | string | |
7 | option env="KERNELVERSION" | |
8 | ||
9 | config DEFCONFIG_LIST | |
10 | string | |
11 | depends on !UML | |
12 | option defconfig_list | |
13 | default "/lib/modules/$UNAME_RELEASE/.config" | |
14 | default "/etc/kernel-config" | |
15 | default "/boot/config-$UNAME_RELEASE" | |
16 | default "$ARCH_DEFCONFIG" | |
17 | default "arch/$ARCH/defconfig" | |
18 | ||
19 | config CONSTRUCTORS | |
20 | bool | |
21 | depends on !UML | |
22 | ||
23 | config IRQ_WORK | |
24 | bool | |
25 | ||
26 | config BUILDTIME_EXTABLE_SORT | |
27 | bool | |
28 | ||
29 | config THREAD_INFO_IN_TASK | |
30 | bool | |
31 | help | |
32 | Select this to move thread_info off the stack into task_struct. To | |
33 | make this work, an arch will need to remove all thread_info fields | |
34 | except flags and fix any runtime bugs. | |
35 | ||
36 | One subtle change that will be needed is to use try_get_task_stack() | |
37 | and put_task_stack() in save_thread_stack_tsk() and get_wchan(). | |
38 | ||
39 | menu "General setup" | |
40 | ||
41 | config BROKEN | |
42 | bool | |
43 | ||
44 | config BROKEN_ON_SMP | |
45 | bool | |
46 | depends on BROKEN || !SMP | |
47 | default y | |
48 | ||
49 | config INIT_ENV_ARG_LIMIT | |
50 | int | |
51 | default 32 if !UML | |
52 | default 128 if UML | |
53 | help | |
54 | Maximum of each of the number of arguments and environment | |
55 | variables passed to init from the kernel command line. | |
56 | ||
57 | ||
58 | config CROSS_COMPILE | |
59 | string "Cross-compiler tool prefix" | |
60 | help | |
61 | Same as running 'make CROSS_COMPILE=prefix-' but stored for | |
62 | default make runs in this kernel build directory. You don't | |
63 | need to set this unless you want the configured kernel build | |
64 | directory to select the cross-compiler automatically. | |
65 | ||
66 | config COMPILE_TEST | |
67 | bool "Compile also drivers which will not load" | |
68 | depends on !UML | |
69 | default n | |
70 | help | |
71 | Some drivers can be compiled on a different platform than they are | |
72 | intended to be run on. Despite they cannot be loaded there (or even | |
73 | when they load they cannot be used due to missing HW support), | |
74 | developers still, opposing to distributors, might want to build such | |
75 | drivers to compile-test them. | |
76 | ||
77 | If you are a developer and want to build everything available, say Y | |
78 | here. If you are a user/distributor, say N here to exclude useless | |
79 | drivers to be distributed. | |
80 | ||
81 | config LOCALVERSION | |
82 | string "Local version - append to kernel release" | |
83 | help | |
84 | Append an extra string to the end of your kernel version. | |
85 | This will show up when you type uname, for example. | |
86 | The string you set here will be appended after the contents of | |
87 | any files with a filename matching localversion* in your | |
88 | object and source tree, in that order. Your total string can | |
89 | be a maximum of 64 characters. | |
90 | ||
91 | config LOCALVERSION_AUTO | |
92 | bool "Automatically append version information to the version string" | |
93 | default y | |
94 | depends on !COMPILE_TEST | |
95 | help | |
96 | This will try to automatically determine if the current tree is a | |
97 | release tree by looking for git tags that belong to the current | |
98 | top of tree revision. | |
99 | ||
100 | A string of the format -gxxxxxxxx will be added to the localversion | |
101 | if a git-based tree is found. The string generated by this will be | |
102 | appended after any matching localversion* files, and after the value | |
103 | set in CONFIG_LOCALVERSION. | |
104 | ||
105 | (The actual string used here is the first eight characters produced | |
106 | by running the command: | |
107 | ||
108 | $ git rev-parse --verify HEAD | |
109 | ||
110 | which is done within the script "scripts/setlocalversion".) | |
111 | ||
112 | config HAVE_KERNEL_GZIP | |
113 | bool | |
114 | ||
115 | config HAVE_KERNEL_BZIP2 | |
116 | bool | |
117 | ||
118 | config HAVE_KERNEL_LZMA | |
119 | bool | |
120 | ||
121 | config HAVE_KERNEL_XZ | |
122 | bool | |
123 | ||
124 | config HAVE_KERNEL_LZO | |
125 | bool | |
126 | ||
127 | config HAVE_KERNEL_LZ4 | |
128 | bool | |
129 | ||
130 | choice | |
131 | prompt "Kernel compression mode" | |
132 | default KERNEL_GZIP | |
133 | depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4 | |
134 | help | |
135 | The linux kernel is a kind of self-extracting executable. | |
136 | Several compression algorithms are available, which differ | |
137 | in efficiency, compression and decompression speed. | |
138 | Compression speed is only relevant when building a kernel. | |
139 | Decompression speed is relevant at each boot. | |
140 | ||
141 | If you have any problems with bzip2 or lzma compressed | |
142 | kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older | |
143 | version of this functionality (bzip2 only), for 2.4, was | |
144 | supplied by Christian Ludwig) | |
145 | ||
146 | High compression options are mostly useful for users, who | |
147 | are low on disk space (embedded systems), but for whom ram | |
148 | size matters less. | |
149 | ||
150 | If in doubt, select 'gzip' | |
151 | ||
152 | config KERNEL_GZIP | |
153 | bool "Gzip" | |
154 | depends on HAVE_KERNEL_GZIP | |
155 | help | |
156 | The old and tried gzip compression. It provides a good balance | |
157 | between compression ratio and decompression speed. | |
158 | ||
159 | config KERNEL_BZIP2 | |
160 | bool "Bzip2" | |
161 | depends on HAVE_KERNEL_BZIP2 | |
162 | help | |
163 | Its compression ratio and speed is intermediate. | |
164 | Decompression speed is slowest among the choices. The kernel | |
165 | size is about 10% smaller with bzip2, in comparison to gzip. | |
166 | Bzip2 uses a large amount of memory. For modern kernels you | |
167 | will need at least 8MB RAM or more for booting. | |
168 | ||
169 | config KERNEL_LZMA | |
170 | bool "LZMA" | |
171 | depends on HAVE_KERNEL_LZMA | |
172 | help | |
173 | This compression algorithm's ratio is best. Decompression speed | |
174 | is between gzip and bzip2. Compression is slowest. | |
175 | The kernel size is about 33% smaller with LZMA in comparison to gzip. | |
176 | ||
177 | config KERNEL_XZ | |
178 | bool "XZ" | |
179 | depends on HAVE_KERNEL_XZ | |
180 | help | |
181 | XZ uses the LZMA2 algorithm and instruction set specific | |
182 | BCJ filters which can improve compression ratio of executable | |
183 | code. The size of the kernel is about 30% smaller with XZ in | |
184 | comparison to gzip. On architectures for which there is a BCJ | |
185 | filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ | |
186 | will create a few percent smaller kernel than plain LZMA. | |
187 | ||
188 | The speed is about the same as with LZMA: The decompression | |
189 | speed of XZ is better than that of bzip2 but worse than gzip | |
190 | and LZO. Compression is slow. | |
191 | ||
192 | config KERNEL_LZO | |
193 | bool "LZO" | |
194 | depends on HAVE_KERNEL_LZO | |
195 | help | |
196 | Its compression ratio is the poorest among the choices. The kernel | |
197 | size is about 10% bigger than gzip; however its speed | |
198 | (both compression and decompression) is the fastest. | |
199 | ||
200 | config KERNEL_LZ4 | |
201 | bool "LZ4" | |
202 | depends on HAVE_KERNEL_LZ4 | |
203 | help | |
204 | LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. | |
205 | A preliminary version of LZ4 de/compression tool is available at | |
206 | <https://code.google.com/p/lz4/>. | |
207 | ||
208 | Its compression ratio is worse than LZO. The size of the kernel | |
209 | is about 8% bigger than LZO. But the decompression speed is | |
210 | faster than LZO. | |
211 | ||
212 | endchoice | |
213 | ||
214 | config DEFAULT_HOSTNAME | |
215 | string "Default hostname" | |
216 | default "(none)" | |
217 | help | |
218 | This option determines the default system hostname before userspace | |
219 | calls sethostname(2). The kernel traditionally uses "(none)" here, | |
220 | but you may wish to use a different default here to make a minimal | |
221 | system more usable with less configuration. | |
222 | ||
223 | config SWAP | |
224 | bool "Support for paging of anonymous memory (swap)" | |
225 | depends on MMU && BLOCK | |
226 | default y | |
227 | help | |
228 | This option allows you to choose whether you want to have support | |
229 | for so called swap devices or swap files in your kernel that are | |
230 | used to provide more virtual memory than the actual RAM present | |
231 | in your computer. If unsure say Y. | |
232 | ||
233 | config SYSVIPC | |
234 | bool "System V IPC" | |
235 | ---help--- | |
236 | Inter Process Communication is a suite of library functions and | |
237 | system calls which let processes (running programs) synchronize and | |
238 | exchange information. It is generally considered to be a good thing, | |
239 | and some programs won't run unless you say Y here. In particular, if | |
240 | you want to run the DOS emulator dosemu under Linux (read the | |
241 | DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>), | |
242 | you'll need to say Y here. | |
243 | ||
244 | You can find documentation about IPC with "info ipc" and also in | |
245 | section 6.4 of the Linux Programmer's Guide, available from | |
246 | <http://www.tldp.org/guides.html>. | |
247 | ||
248 | config SYSVIPC_SYSCTL | |
249 | bool | |
250 | depends on SYSVIPC | |
251 | depends on SYSCTL | |
252 | default y | |
253 | ||
254 | config POSIX_MQUEUE | |
255 | bool "POSIX Message Queues" | |
256 | depends on NET | |
257 | ---help--- | |
258 | POSIX variant of message queues is a part of IPC. In POSIX message | |
259 | queues every message has a priority which decides about succession | |
260 | of receiving it by a process. If you want to compile and run | |
261 | programs written e.g. for Solaris with use of its POSIX message | |
262 | queues (functions mq_*) say Y here. | |
263 | ||
264 | POSIX message queues are visible as a filesystem called 'mqueue' | |
265 | and can be mounted somewhere if you want to do filesystem | |
266 | operations on message queues. | |
267 | ||
268 | If unsure, say Y. | |
269 | ||
270 | config POSIX_MQUEUE_SYSCTL | |
271 | bool | |
272 | depends on POSIX_MQUEUE | |
273 | depends on SYSCTL | |
274 | default y | |
275 | ||
276 | config CROSS_MEMORY_ATTACH | |
277 | bool "Enable process_vm_readv/writev syscalls" | |
278 | depends on MMU | |
279 | default y | |
280 | help | |
281 | Enabling this option adds the system calls process_vm_readv and | |
282 | process_vm_writev which allow a process with the correct privileges | |
283 | to directly read from or write to another process' address space. | |
284 | See the man page for more details. | |
285 | ||
286 | config FHANDLE | |
287 | bool "open by fhandle syscalls" if EXPERT | |
288 | select EXPORTFS | |
289 | default y | |
290 | help | |
291 | If you say Y here, a user level program will be able to map | |
292 | file names to handle and then later use the handle for | |
293 | different file system operations. This is useful in implementing | |
294 | userspace file servers, which now track files using handles instead | |
295 | of names. The handle would remain the same even if file names | |
296 | get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2) | |
297 | syscalls. | |
298 | ||
299 | config USELIB | |
300 | bool "uselib syscall" | |
301 | def_bool ALPHA || M68K || SPARC || X86_32 || IA32_EMULATION | |
302 | help | |
303 | This option enables the uselib syscall, a system call used in the | |
304 | dynamic linker from libc5 and earlier. glibc does not use this | |
305 | system call. If you intend to run programs built on libc5 or | |
306 | earlier, you may need to enable this syscall. Current systems | |
307 | running glibc can safely disable this. | |
308 | ||
309 | config AUDIT | |
310 | bool "Auditing support" | |
311 | depends on NET | |
312 | help | |
313 | Enable auditing infrastructure that can be used with another | |
314 | kernel subsystem, such as SELinux (which requires this for | |
315 | logging of avc messages output). System call auditing is included | |
316 | on architectures which support it. | |
317 | ||
318 | config HAVE_ARCH_AUDITSYSCALL | |
319 | bool | |
320 | ||
321 | config AUDITSYSCALL | |
322 | def_bool y | |
323 | depends on AUDIT && HAVE_ARCH_AUDITSYSCALL | |
324 | ||
325 | config AUDIT_WATCH | |
326 | def_bool y | |
327 | depends on AUDITSYSCALL | |
328 | select FSNOTIFY | |
329 | ||
330 | config AUDIT_TREE | |
331 | def_bool y | |
332 | depends on AUDITSYSCALL | |
333 | select FSNOTIFY | |
334 | ||
335 | source "kernel/irq/Kconfig" | |
336 | source "kernel/time/Kconfig" | |
337 | ||
338 | menu "CPU/Task time and stats accounting" | |
339 | ||
340 | config VIRT_CPU_ACCOUNTING | |
341 | bool | |
342 | ||
343 | choice | |
344 | prompt "Cputime accounting" | |
345 | default TICK_CPU_ACCOUNTING if !PPC64 | |
346 | default VIRT_CPU_ACCOUNTING_NATIVE if PPC64 | |
347 | ||
348 | # Kind of a stub config for the pure tick based cputime accounting | |
349 | config TICK_CPU_ACCOUNTING | |
350 | bool "Simple tick based cputime accounting" | |
351 | depends on !S390 && !NO_HZ_FULL | |
352 | help | |
353 | This is the basic tick based cputime accounting that maintains | |
354 | statistics about user, system and idle time spent on per jiffies | |
355 | granularity. | |
356 | ||
357 | If unsure, say Y. | |
358 | ||
359 | config VIRT_CPU_ACCOUNTING_NATIVE | |
360 | bool "Deterministic task and CPU time accounting" | |
361 | depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL | |
362 | select VIRT_CPU_ACCOUNTING | |
363 | help | |
364 | Select this option to enable more accurate task and CPU time | |
365 | accounting. This is done by reading a CPU counter on each | |
366 | kernel entry and exit and on transitions within the kernel | |
367 | between system, softirq and hardirq state, so there is a | |
368 | small performance impact. In the case of s390 or IBM POWER > 5, | |
369 | this also enables accounting of stolen time on logically-partitioned | |
370 | systems. | |
371 | ||
372 | config VIRT_CPU_ACCOUNTING_GEN | |
373 | bool "Full dynticks CPU time accounting" | |
374 | depends on HAVE_CONTEXT_TRACKING | |
375 | depends on HAVE_VIRT_CPU_ACCOUNTING_GEN | |
376 | select VIRT_CPU_ACCOUNTING | |
377 | select CONTEXT_TRACKING | |
378 | help | |
379 | Select this option to enable task and CPU time accounting on full | |
380 | dynticks systems. This accounting is implemented by watching every | |
381 | kernel-user boundaries using the context tracking subsystem. | |
382 | The accounting is thus performed at the expense of some significant | |
383 | overhead. | |
384 | ||
385 | For now this is only useful if you are working on the full | |
386 | dynticks subsystem development. | |
387 | ||
388 | If unsure, say N. | |
389 | ||
390 | endchoice | |
391 | ||
392 | config IRQ_TIME_ACCOUNTING | |
393 | bool "Fine granularity task level IRQ time accounting" | |
394 | depends on HAVE_IRQ_TIME_ACCOUNTING && !VIRT_CPU_ACCOUNTING_NATIVE | |
395 | help | |
396 | Select this option to enable fine granularity task irq time | |
397 | accounting. This is done by reading a timestamp on each | |
398 | transitions between softirq and hardirq state, so there can be a | |
399 | small performance impact. | |
400 | ||
401 | If in doubt, say N here. | |
402 | ||
403 | config BSD_PROCESS_ACCT | |
404 | bool "BSD Process Accounting" | |
405 | depends on MULTIUSER | |
406 | help | |
407 | If you say Y here, a user level program will be able to instruct the | |
408 | kernel (via a special system call) to write process accounting | |
409 | information to a file: whenever a process exits, information about | |
410 | that process will be appended to the file by the kernel. The | |
411 | information includes things such as creation time, owning user, | |
412 | command name, memory usage, controlling terminal etc. (the complete | |
413 | list is in the struct acct in <file:include/linux/acct.h>). It is | |
414 | up to the user level program to do useful things with this | |
415 | information. This is generally a good idea, so say Y. | |
416 | ||
417 | config BSD_PROCESS_ACCT_V3 | |
418 | bool "BSD Process Accounting version 3 file format" | |
419 | depends on BSD_PROCESS_ACCT | |
420 | default n | |
421 | help | |
422 | If you say Y here, the process accounting information is written | |
423 | in a new file format that also logs the process IDs of each | |
424 | process and it's parent. Note that this file format is incompatible | |
425 | with previous v0/v1/v2 file formats, so you will need updated tools | |
426 | for processing it. A preliminary version of these tools is available | |
427 | at <http://www.gnu.org/software/acct/>. | |
428 | ||
429 | config TASKSTATS | |
430 | bool "Export task/process statistics through netlink" | |
431 | depends on NET | |
432 | depends on MULTIUSER | |
433 | default n | |
434 | help | |
435 | Export selected statistics for tasks/processes through the | |
436 | generic netlink interface. Unlike BSD process accounting, the | |
437 | statistics are available during the lifetime of tasks/processes as | |
438 | responses to commands. Like BSD accounting, they are sent to user | |
439 | space on task exit. | |
440 | ||
441 | Say N if unsure. | |
442 | ||
443 | config TASK_DELAY_ACCT | |
444 | bool "Enable per-task delay accounting" | |
445 | depends on TASKSTATS | |
446 | select SCHED_INFO | |
447 | help | |
448 | Collect information on time spent by a task waiting for system | |
449 | resources like cpu, synchronous block I/O completion and swapping | |
450 | in pages. Such statistics can help in setting a task's priorities | |
451 | relative to other tasks for cpu, io, rss limits etc. | |
452 | ||
453 | Say N if unsure. | |
454 | ||
455 | config TASK_XACCT | |
456 | bool "Enable extended accounting over taskstats" | |
457 | depends on TASKSTATS | |
458 | help | |
459 | Collect extended task accounting data and send the data | |
460 | to userland for processing over the taskstats interface. | |
461 | ||
462 | Say N if unsure. | |
463 | ||
464 | config TASK_IO_ACCOUNTING | |
465 | bool "Enable per-task storage I/O accounting" | |
466 | depends on TASK_XACCT | |
467 | help | |
468 | Collect information on the number of bytes of storage I/O which this | |
469 | task has caused. | |
470 | ||
471 | Say N if unsure. | |
472 | ||
473 | endmenu # "CPU/Task time and stats accounting" | |
474 | ||
475 | menu "RCU Subsystem" | |
476 | ||
477 | config TREE_RCU | |
478 | bool | |
479 | default y if !PREEMPT && SMP | |
480 | help | |
481 | This option selects the RCU implementation that is | |
482 | designed for very large SMP system with hundreds or | |
483 | thousands of CPUs. It also scales down nicely to | |
484 | smaller systems. | |
485 | ||
486 | config PREEMPT_RCU | |
487 | bool | |
488 | default y if PREEMPT | |
489 | help | |
490 | This option selects the RCU implementation that is | |
491 | designed for very large SMP systems with hundreds or | |
492 | thousands of CPUs, but for which real-time response | |
493 | is also required. It also scales down nicely to | |
494 | smaller systems. | |
495 | ||
496 | Select this option if you are unsure. | |
497 | ||
498 | config TINY_RCU | |
499 | bool | |
500 | default y if !PREEMPT && !SMP | |
501 | help | |
502 | This option selects the RCU implementation that is | |
503 | designed for UP systems from which real-time response | |
504 | is not required. This option greatly reduces the | |
505 | memory footprint of RCU. | |
506 | ||
507 | config RCU_EXPERT | |
508 | bool "Make expert-level adjustments to RCU configuration" | |
509 | default n | |
510 | help | |
511 | This option needs to be enabled if you wish to make | |
512 | expert-level adjustments to RCU configuration. By default, | |
513 | no such adjustments can be made, which has the often-beneficial | |
514 | side-effect of preventing "make oldconfig" from asking you all | |
515 | sorts of detailed questions about how you would like numerous | |
516 | obscure RCU options to be set up. | |
517 | ||
518 | Say Y if you need to make expert-level adjustments to RCU. | |
519 | ||
520 | Say N if you are unsure. | |
521 | ||
522 | config SRCU | |
523 | bool | |
524 | help | |
525 | This option selects the sleepable version of RCU. This version | |
526 | permits arbitrary sleeping or blocking within RCU read-side critical | |
527 | sections. | |
528 | ||
529 | config TASKS_RCU | |
530 | bool | |
531 | default n | |
532 | select SRCU | |
533 | help | |
534 | This option enables a task-based RCU implementation that uses | |
535 | only voluntary context switch (not preemption!), idle, and | |
536 | user-mode execution as quiescent states. | |
537 | ||
538 | config RCU_STALL_COMMON | |
539 | def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE ) | |
540 | help | |
541 | This option enables RCU CPU stall code that is common between | |
542 | the TINY and TREE variants of RCU. The purpose is to allow | |
543 | the tiny variants to disable RCU CPU stall warnings, while | |
544 | making these warnings mandatory for the tree variants. | |
545 | ||
546 | config CONTEXT_TRACKING | |
547 | bool | |
548 | ||
549 | config CONTEXT_TRACKING_FORCE | |
550 | bool "Force context tracking" | |
551 | depends on CONTEXT_TRACKING | |
552 | default y if !NO_HZ_FULL | |
553 | help | |
554 | The major pre-requirement for full dynticks to work is to | |
555 | support the context tracking subsystem. But there are also | |
556 | other dependencies to provide in order to make the full | |
557 | dynticks working. | |
558 | ||
559 | This option stands for testing when an arch implements the | |
560 | context tracking backend but doesn't yet fullfill all the | |
561 | requirements to make the full dynticks feature working. | |
562 | Without the full dynticks, there is no way to test the support | |
563 | for context tracking and the subsystems that rely on it: RCU | |
564 | userspace extended quiescent state and tickless cputime | |
565 | accounting. This option copes with the absence of the full | |
566 | dynticks subsystem by forcing the context tracking on all | |
567 | CPUs in the system. | |
568 | ||
569 | Say Y only if you're working on the development of an | |
570 | architecture backend for the context tracking. | |
571 | ||
572 | Say N otherwise, this option brings an overhead that you | |
573 | don't want in production. | |
574 | ||
575 | ||
576 | config RCU_FANOUT | |
577 | int "Tree-based hierarchical RCU fanout value" | |
578 | range 2 64 if 64BIT | |
579 | range 2 32 if !64BIT | |
580 | depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT | |
581 | default 64 if 64BIT | |
582 | default 32 if !64BIT | |
583 | help | |
584 | This option controls the fanout of hierarchical implementations | |
585 | of RCU, allowing RCU to work efficiently on machines with | |
586 | large numbers of CPUs. This value must be at least the fourth | |
587 | root of NR_CPUS, which allows NR_CPUS to be insanely large. | |
588 | The default value of RCU_FANOUT should be used for production | |
589 | systems, but if you are stress-testing the RCU implementation | |
590 | itself, small RCU_FANOUT values allow you to test large-system | |
591 | code paths on small(er) systems. | |
592 | ||
593 | Select a specific number if testing RCU itself. | |
594 | Take the default if unsure. | |
595 | ||
596 | config RCU_FANOUT_LEAF | |
597 | int "Tree-based hierarchical RCU leaf-level fanout value" | |
598 | range 2 64 if 64BIT | |
599 | range 2 32 if !64BIT | |
600 | depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT | |
601 | default 16 | |
602 | help | |
603 | This option controls the leaf-level fanout of hierarchical | |
604 | implementations of RCU, and allows trading off cache misses | |
605 | against lock contention. Systems that synchronize their | |
606 | scheduling-clock interrupts for energy-efficiency reasons will | |
607 | want the default because the smaller leaf-level fanout keeps | |
608 | lock contention levels acceptably low. Very large systems | |
609 | (hundreds or thousands of CPUs) will instead want to set this | |
610 | value to the maximum value possible in order to reduce the | |
611 | number of cache misses incurred during RCU's grace-period | |
612 | initialization. These systems tend to run CPU-bound, and thus | |
613 | are not helped by synchronized interrupts, and thus tend to | |
614 | skew them, which reduces lock contention enough that large | |
615 | leaf-level fanouts work well. | |
616 | ||
617 | Select a specific number if testing RCU itself. | |
618 | ||
619 | Select the maximum permissible value for large systems. | |
620 | ||
621 | Take the default if unsure. | |
622 | ||
623 | config RCU_FAST_NO_HZ | |
624 | bool "Accelerate last non-dyntick-idle CPU's grace periods" | |
625 | depends on NO_HZ_COMMON && SMP && RCU_EXPERT | |
626 | default n | |
627 | help | |
628 | This option permits CPUs to enter dynticks-idle state even if | |
629 | they have RCU callbacks queued, and prevents RCU from waking | |
630 | these CPUs up more than roughly once every four jiffies (by | |
631 | default, you can adjust this using the rcutree.rcu_idle_gp_delay | |
632 | parameter), thus improving energy efficiency. On the other | |
633 | hand, this option increases the duration of RCU grace periods, | |
634 | for example, slowing down synchronize_rcu(). | |
635 | ||
636 | Say Y if energy efficiency is critically important, and you | |
637 | don't care about increased grace-period durations. | |
638 | ||
639 | Say N if you are unsure. | |
640 | ||
641 | config TREE_RCU_TRACE | |
642 | def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU ) | |
643 | select DEBUG_FS | |
644 | help | |
645 | This option provides tracing for the TREE_RCU and | |
646 | PREEMPT_RCU implementations, permitting Makefile to | |
647 | trivially select kernel/rcutree_trace.c. | |
648 | ||
649 | config RCU_BOOST | |
650 | bool "Enable RCU priority boosting" | |
651 | depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT | |
652 | default n | |
653 | help | |
654 | This option boosts the priority of preempted RCU readers that | |
655 | block the current preemptible RCU grace period for too long. | |
656 | This option also prevents heavy loads from blocking RCU | |
657 | callback invocation for all flavors of RCU. | |
658 | ||
659 | Say Y here if you are working with real-time apps or heavy loads | |
660 | Say N here if you are unsure. | |
661 | ||
662 | config RCU_KTHREAD_PRIO | |
663 | int "Real-time priority to use for RCU worker threads" | |
664 | range 1 99 if RCU_BOOST | |
665 | range 0 99 if !RCU_BOOST | |
666 | default 1 if RCU_BOOST | |
667 | default 0 if !RCU_BOOST | |
668 | depends on RCU_EXPERT | |
669 | help | |
670 | This option specifies the SCHED_FIFO priority value that will be | |
671 | assigned to the rcuc/n and rcub/n threads and is also the value | |
672 | used for RCU_BOOST (if enabled). If you are working with a | |
673 | real-time application that has one or more CPU-bound threads | |
674 | running at a real-time priority level, you should set | |
675 | RCU_KTHREAD_PRIO to a priority higher than the highest-priority | |
676 | real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO | |
677 | value of 1 is appropriate in the common case, which is real-time | |
678 | applications that do not have any CPU-bound threads. | |
679 | ||
680 | Some real-time applications might not have a single real-time | |
681 | thread that saturates a given CPU, but instead might have | |
682 | multiple real-time threads that, taken together, fully utilize | |
683 | that CPU. In this case, you should set RCU_KTHREAD_PRIO to | |
684 | a priority higher than the lowest-priority thread that is | |
685 | conspiring to prevent the CPU from running any non-real-time | |
686 | tasks. For example, if one thread at priority 10 and another | |
687 | thread at priority 5 are between themselves fully consuming | |
688 | the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be | |
689 | set to priority 6 or higher. | |
690 | ||
691 | Specify the real-time priority, or take the default if unsure. | |
692 | ||
693 | config RCU_BOOST_DELAY | |
694 | int "Milliseconds to delay boosting after RCU grace-period start" | |
695 | range 0 3000 | |
696 | depends on RCU_BOOST | |
697 | default 500 | |
698 | help | |
699 | This option specifies the time to wait after the beginning of | |
700 | a given grace period before priority-boosting preempted RCU | |
701 | readers blocking that grace period. Note that any RCU reader | |
702 | blocking an expedited RCU grace period is boosted immediately. | |
703 | ||
704 | Accept the default if unsure. | |
705 | ||
706 | config RCU_NOCB_CPU | |
707 | bool "Offload RCU callback processing from boot-selected CPUs" | |
708 | depends on TREE_RCU || PREEMPT_RCU | |
709 | depends on RCU_EXPERT || NO_HZ_FULL | |
710 | default n | |
711 | help | |
712 | Use this option to reduce OS jitter for aggressive HPC or | |
713 | real-time workloads. It can also be used to offload RCU | |
714 | callback invocation to energy-efficient CPUs in battery-powered | |
715 | asymmetric multiprocessors. | |
716 | ||
717 | This option offloads callback invocation from the set of | |
718 | CPUs specified at boot time by the rcu_nocbs parameter. | |
719 | For each such CPU, a kthread ("rcuox/N") will be created to | |
720 | invoke callbacks, where the "N" is the CPU being offloaded, | |
721 | and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and | |
722 | "s" for RCU-sched. Nothing prevents this kthread from running | |
723 | on the specified CPUs, but (1) the kthreads may be preempted | |
724 | between each callback, and (2) affinity or cgroups can be used | |
725 | to force the kthreads to run on whatever set of CPUs is desired. | |
726 | ||
727 | Say Y here if you want to help to debug reduced OS jitter. | |
728 | Say N here if you are unsure. | |
729 | ||
730 | choice | |
731 | prompt "Build-forced no-CBs CPUs" | |
732 | default RCU_NOCB_CPU_NONE | |
733 | depends on RCU_NOCB_CPU | |
734 | help | |
735 | This option allows no-CBs CPUs (whose RCU callbacks are invoked | |
736 | from kthreads rather than from softirq context) to be specified | |
737 | at build time. Additional no-CBs CPUs may be specified by | |
738 | the rcu_nocbs= boot parameter. | |
739 | ||
740 | config RCU_NOCB_CPU_NONE | |
741 | bool "No build_forced no-CBs CPUs" | |
742 | help | |
743 | This option does not force any of the CPUs to be no-CBs CPUs. | |
744 | Only CPUs designated by the rcu_nocbs= boot parameter will be | |
745 | no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU | |
746 | kthreads whose names begin with "rcuo". All other CPUs will | |
747 | invoke their own RCU callbacks in softirq context. | |
748 | ||
749 | Select this option if you want to choose no-CBs CPUs at | |
750 | boot time, for example, to allow testing of different no-CBs | |
751 | configurations without having to rebuild the kernel each time. | |
752 | ||
753 | config RCU_NOCB_CPU_ZERO | |
754 | bool "CPU 0 is a build_forced no-CBs CPU" | |
755 | help | |
756 | This option forces CPU 0 to be a no-CBs CPU, so that its RCU | |
757 | callbacks are invoked by a per-CPU kthread whose name begins | |
758 | with "rcuo". Additional CPUs may be designated as no-CBs | |
759 | CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs. | |
760 | All other CPUs will invoke their own RCU callbacks in softirq | |
761 | context. | |
762 | ||
763 | Select this if CPU 0 needs to be a no-CBs CPU for real-time | |
764 | or energy-efficiency reasons, but the real reason it exists | |
765 | is to ensure that randconfig testing covers mixed systems. | |
766 | ||
767 | config RCU_NOCB_CPU_ALL | |
768 | bool "All CPUs are build_forced no-CBs CPUs" | |
769 | help | |
770 | This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs= | |
771 | boot parameter will be ignored. All CPUs' RCU callbacks will | |
772 | be executed in the context of per-CPU rcuo kthreads created for | |
773 | this purpose. Assuming that the kthreads whose names start with | |
774 | "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter | |
775 | on the remaining CPUs, but might decrease memory locality during | |
776 | RCU-callback invocation, thus potentially degrading throughput. | |
777 | ||
778 | Select this if all CPUs need to be no-CBs CPUs for real-time | |
779 | or energy-efficiency reasons. | |
780 | ||
781 | endchoice | |
782 | ||
783 | endmenu # "RCU Subsystem" | |
784 | ||
785 | config BUILD_BIN2C | |
786 | bool | |
787 | default n | |
788 | ||
789 | config IKCONFIG | |
790 | tristate "Kernel .config support" | |
791 | select BUILD_BIN2C | |
792 | ---help--- | |
793 | This option enables the complete Linux kernel ".config" file | |
794 | contents to be saved in the kernel. It provides documentation | |
795 | of which kernel options are used in a running kernel or in an | |
796 | on-disk kernel. This information can be extracted from the kernel | |
797 | image file with the script scripts/extract-ikconfig and used as | |
798 | input to rebuild the current kernel or to build another kernel. | |
799 | It can also be extracted from a running kernel by reading | |
800 | /proc/config.gz if enabled (below). | |
801 | ||
802 | config IKCONFIG_PROC | |
803 | bool "Enable access to .config through /proc/config.gz" | |
804 | depends on IKCONFIG && PROC_FS | |
805 | ---help--- | |
806 | This option enables access to the kernel configuration file | |
807 | through /proc/config.gz. | |
808 | ||
809 | config LOG_BUF_SHIFT | |
810 | int "Kernel log buffer size (16 => 64KB, 17 => 128KB)" | |
811 | range 12 25 | |
812 | default 17 | |
813 | depends on PRINTK | |
814 | help | |
815 | Select the minimal kernel log buffer size as a power of 2. | |
816 | The final size is affected by LOG_CPU_MAX_BUF_SHIFT config | |
817 | parameter, see below. Any higher size also might be forced | |
818 | by "log_buf_len" boot parameter. | |
819 | ||
820 | Examples: | |
821 | 17 => 128 KB | |
822 | 16 => 64 KB | |
823 | 15 => 32 KB | |
824 | 14 => 16 KB | |
825 | 13 => 8 KB | |
826 | 12 => 4 KB | |
827 | ||
828 | config LOG_CPU_MAX_BUF_SHIFT | |
829 | int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)" | |
830 | depends on SMP | |
831 | range 0 21 | |
832 | default 12 if !BASE_SMALL | |
833 | default 0 if BASE_SMALL | |
834 | depends on PRINTK | |
835 | help | |
836 | This option allows to increase the default ring buffer size | |
837 | according to the number of CPUs. The value defines the contribution | |
838 | of each CPU as a power of 2. The used space is typically only few | |
839 | lines however it might be much more when problems are reported, | |
840 | e.g. backtraces. | |
841 | ||
842 | The increased size means that a new buffer has to be allocated and | |
843 | the original static one is unused. It makes sense only on systems | |
844 | with more CPUs. Therefore this value is used only when the sum of | |
845 | contributions is greater than the half of the default kernel ring | |
846 | buffer as defined by LOG_BUF_SHIFT. The default values are set | |
847 | so that more than 64 CPUs are needed to trigger the allocation. | |
848 | ||
849 | Also this option is ignored when "log_buf_len" kernel parameter is | |
850 | used as it forces an exact (power of two) size of the ring buffer. | |
851 | ||
852 | The number of possible CPUs is used for this computation ignoring | |
853 | hotplugging making the computation optimal for the worst case | |
854 | scenario while allowing a simple algorithm to be used from bootup. | |
855 | ||
856 | Examples shift values and their meaning: | |
857 | 17 => 128 KB for each CPU | |
858 | 16 => 64 KB for each CPU | |
859 | 15 => 32 KB for each CPU | |
860 | 14 => 16 KB for each CPU | |
861 | 13 => 8 KB for each CPU | |
862 | 12 => 4 KB for each CPU | |
863 | ||
864 | config NMI_LOG_BUF_SHIFT | |
865 | int "Temporary per-CPU NMI log buffer size (12 => 4KB, 13 => 8KB)" | |
866 | range 10 21 | |
867 | default 13 | |
868 | depends on PRINTK_NMI | |
869 | help | |
870 | Select the size of a per-CPU buffer where NMI messages are temporary | |
871 | stored. They are copied to the main log buffer in a safe context | |
872 | to avoid a deadlock. The value defines the size as a power of 2. | |
873 | ||
874 | NMI messages are rare and limited. The largest one is when | |
875 | a backtrace is printed. It usually fits into 4KB. Select | |
876 | 8KB if you want to be on the safe side. | |
877 | ||
878 | Examples: | |
879 | 17 => 128 KB for each CPU | |
880 | 16 => 64 KB for each CPU | |
881 | 15 => 32 KB for each CPU | |
882 | 14 => 16 KB for each CPU | |
883 | 13 => 8 KB for each CPU | |
884 | 12 => 4 KB for each CPU | |
885 | ||
886 | # | |
887 | # Architectures with an unreliable sched_clock() should select this: | |
888 | # | |
889 | config HAVE_UNSTABLE_SCHED_CLOCK | |
890 | bool | |
891 | ||
892 | config GENERIC_SCHED_CLOCK | |
893 | bool | |
894 | ||
895 | # | |
896 | # For architectures that want to enable the support for NUMA-affine scheduler | |
897 | # balancing logic: | |
898 | # | |
899 | config ARCH_SUPPORTS_NUMA_BALANCING | |
900 | bool | |
901 | ||
902 | # | |
903 | # For architectures that prefer to flush all TLBs after a number of pages | |
904 | # are unmapped instead of sending one IPI per page to flush. The architecture | |
905 | # must provide guarantees on what happens if a clean TLB cache entry is | |
906 | # written after the unmap. Details are in mm/rmap.c near the check for | |
907 | # should_defer_flush. The architecture should also consider if the full flush | |
908 | # and the refill costs are offset by the savings of sending fewer IPIs. | |
909 | config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH | |
910 | bool | |
911 | ||
912 | # | |
913 | # For architectures that know their GCC __int128 support is sound | |
914 | # | |
915 | config ARCH_SUPPORTS_INT128 | |
916 | bool | |
917 | ||
918 | # For architectures that (ab)use NUMA to represent different memory regions | |
919 | # all cpu-local but of different latencies, such as SuperH. | |
920 | # | |
921 | config ARCH_WANT_NUMA_VARIABLE_LOCALITY | |
922 | bool | |
923 | ||
924 | config NUMA_BALANCING | |
925 | bool "Memory placement aware NUMA scheduler" | |
926 | depends on ARCH_SUPPORTS_NUMA_BALANCING | |
927 | depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY | |
928 | depends on SMP && NUMA && MIGRATION | |
929 | help | |
930 | This option adds support for automatic NUMA aware memory/task placement. | |
931 | The mechanism is quite primitive and is based on migrating memory when | |
932 | it has references to the node the task is running on. | |
933 | ||
934 | This system will be inactive on UMA systems. | |
935 | ||
936 | config NUMA_BALANCING_DEFAULT_ENABLED | |
937 | bool "Automatically enable NUMA aware memory/task placement" | |
938 | default y | |
939 | depends on NUMA_BALANCING | |
940 | help | |
941 | If set, automatic NUMA balancing will be enabled if running on a NUMA | |
942 | machine. | |
943 | ||
944 | menuconfig CGROUPS | |
945 | bool "Control Group support" | |
946 | select KERNFS | |
947 | help | |
948 | This option adds support for grouping sets of processes together, for | |
949 | use with process control subsystems such as Cpusets, CFS, memory | |
950 | controls or device isolation. | |
951 | See | |
952 | - Documentation/scheduler/sched-design-CFS.txt (CFS) | |
953 | - Documentation/cgroup-v1/ (features for grouping, isolation | |
954 | and resource control) | |
955 | ||
956 | Say N if unsure. | |
957 | ||
958 | if CGROUPS | |
959 | ||
960 | config PAGE_COUNTER | |
961 | bool | |
962 | ||
963 | config MEMCG | |
964 | bool "Memory controller" | |
965 | select PAGE_COUNTER | |
966 | select EVENTFD | |
967 | help | |
968 | Provides control over the memory footprint of tasks in a cgroup. | |
969 | ||
970 | config MEMCG_SWAP | |
971 | bool "Swap controller" | |
972 | depends on MEMCG && SWAP | |
973 | help | |
974 | Provides control over the swap space consumed by tasks in a cgroup. | |
975 | ||
976 | config MEMCG_SWAP_ENABLED | |
977 | bool "Swap controller enabled by default" | |
978 | depends on MEMCG_SWAP | |
979 | default y | |
980 | help | |
981 | Memory Resource Controller Swap Extension comes with its price in | |
982 | a bigger memory consumption. General purpose distribution kernels | |
983 | which want to enable the feature but keep it disabled by default | |
984 | and let the user enable it by swapaccount=1 boot command line | |
985 | parameter should have this option unselected. | |
986 | For those who want to have the feature enabled by default should | |
987 | select this option (if, for some reason, they need to disable it | |
988 | then swapaccount=0 does the trick). | |
989 | ||
990 | config BLK_CGROUP | |
991 | bool "IO controller" | |
992 | depends on BLOCK | |
993 | default n | |
994 | ---help--- | |
995 | Generic block IO controller cgroup interface. This is the common | |
996 | cgroup interface which should be used by various IO controlling | |
997 | policies. | |
998 | ||
999 | Currently, CFQ IO scheduler uses it to recognize task groups and | |
1000 | control disk bandwidth allocation (proportional time slice allocation) | |
1001 | to such task groups. It is also used by bio throttling logic in | |
1002 | block layer to implement upper limit in IO rates on a device. | |
1003 | ||
1004 | This option only enables generic Block IO controller infrastructure. | |
1005 | One needs to also enable actual IO controlling logic/policy. For | |
1006 | enabling proportional weight division of disk bandwidth in CFQ, set | |
1007 | CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set | |
1008 | CONFIG_BLK_DEV_THROTTLING=y. | |
1009 | ||
1010 | See Documentation/cgroup-v1/blkio-controller.txt for more information. | |
1011 | ||
1012 | config DEBUG_BLK_CGROUP | |
1013 | bool "IO controller debugging" | |
1014 | depends on BLK_CGROUP | |
1015 | default n | |
1016 | ---help--- | |
1017 | Enable some debugging help. Currently it exports additional stat | |
1018 | files in a cgroup which can be useful for debugging. | |
1019 | ||
1020 | config CGROUP_WRITEBACK | |
1021 | bool | |
1022 | depends on MEMCG && BLK_CGROUP | |
1023 | default y | |
1024 | ||
1025 | menuconfig CGROUP_SCHED | |
1026 | bool "CPU controller" | |
1027 | default n | |
1028 | help | |
1029 | This feature lets CPU scheduler recognize task groups and control CPU | |
1030 | bandwidth allocation to such task groups. It uses cgroups to group | |
1031 | tasks. | |
1032 | ||
1033 | if CGROUP_SCHED | |
1034 | config FAIR_GROUP_SCHED | |
1035 | bool "Group scheduling for SCHED_OTHER" | |
1036 | depends on CGROUP_SCHED | |
1037 | default CGROUP_SCHED | |
1038 | ||
1039 | config CFS_BANDWIDTH | |
1040 | bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED" | |
1041 | depends on FAIR_GROUP_SCHED | |
1042 | default n | |
1043 | help | |
1044 | This option allows users to define CPU bandwidth rates (limits) for | |
1045 | tasks running within the fair group scheduler. Groups with no limit | |
1046 | set are considered to be unconstrained and will run with no | |
1047 | restriction. | |
1048 | See tip/Documentation/scheduler/sched-bwc.txt for more information. | |
1049 | ||
1050 | config RT_GROUP_SCHED | |
1051 | bool "Group scheduling for SCHED_RR/FIFO" | |
1052 | depends on CGROUP_SCHED | |
1053 | default n | |
1054 | help | |
1055 | This feature lets you explicitly allocate real CPU bandwidth | |
1056 | to task groups. If enabled, it will also make it impossible to | |
1057 | schedule realtime tasks for non-root users until you allocate | |
1058 | realtime bandwidth for them. | |
1059 | See Documentation/scheduler/sched-rt-group.txt for more information. | |
1060 | ||
1061 | endif #CGROUP_SCHED | |
1062 | ||
1063 | config CGROUP_PIDS | |
1064 | bool "PIDs controller" | |
1065 | help | |
1066 | Provides enforcement of process number limits in the scope of a | |
1067 | cgroup. Any attempt to fork more processes than is allowed in the | |
1068 | cgroup will fail. PIDs are fundamentally a global resource because it | |
1069 | is fairly trivial to reach PID exhaustion before you reach even a | |
1070 | conservative kmemcg limit. As a result, it is possible to grind a | |
1071 | system to halt without being limited by other cgroup policies. The | |
1072 | PIDs controller is designed to stop this from happening. | |
1073 | ||
1074 | It should be noted that organisational operations (such as attaching | |
1075 | to a cgroup hierarchy will *not* be blocked by the PIDs controller), | |
1076 | since the PIDs limit only affects a process's ability to fork, not to | |
1077 | attach to a cgroup. | |
1078 | ||
1079 | config CGROUP_FREEZER | |
1080 | bool "Freezer controller" | |
1081 | help | |
1082 | Provides a way to freeze and unfreeze all tasks in a | |
1083 | cgroup. | |
1084 | ||
1085 | This option affects the ORIGINAL cgroup interface. The cgroup2 memory | |
1086 | controller includes important in-kernel memory consumers per default. | |
1087 | ||
1088 | If you're using cgroup2, say N. | |
1089 | ||
1090 | config CGROUP_HUGETLB | |
1091 | bool "HugeTLB controller" | |
1092 | depends on HUGETLB_PAGE | |
1093 | select PAGE_COUNTER | |
1094 | default n | |
1095 | help | |
1096 | Provides a cgroup controller for HugeTLB pages. | |
1097 | When you enable this, you can put a per cgroup limit on HugeTLB usage. | |
1098 | The limit is enforced during page fault. Since HugeTLB doesn't | |
1099 | support page reclaim, enforcing the limit at page fault time implies | |
1100 | that, the application will get SIGBUS signal if it tries to access | |
1101 | HugeTLB pages beyond its limit. This requires the application to know | |
1102 | beforehand how much HugeTLB pages it would require for its use. The | |
1103 | control group is tracked in the third page lru pointer. This means | |
1104 | that we cannot use the controller with huge page less than 3 pages. | |
1105 | ||
1106 | config CPUSETS | |
1107 | bool "Cpuset controller" | |
1108 | help | |
1109 | This option will let you create and manage CPUSETs which | |
1110 | allow dynamically partitioning a system into sets of CPUs and | |
1111 | Memory Nodes and assigning tasks to run only within those sets. | |
1112 | This is primarily useful on large SMP or NUMA systems. | |
1113 | ||
1114 | Say N if unsure. | |
1115 | ||
1116 | config PROC_PID_CPUSET | |
1117 | bool "Include legacy /proc/<pid>/cpuset file" | |
1118 | depends on CPUSETS | |
1119 | default y | |
1120 | ||
1121 | config CGROUP_DEVICE | |
1122 | bool "Device controller" | |
1123 | help | |
1124 | Provides a cgroup controller implementing whitelists for | |
1125 | devices which a process in the cgroup can mknod or open. | |
1126 | ||
1127 | config CGROUP_CPUACCT | |
1128 | bool "Simple CPU accounting controller" | |
1129 | help | |
1130 | Provides a simple controller for monitoring the | |
1131 | total CPU consumed by the tasks in a cgroup. | |
1132 | ||
1133 | config CGROUP_PERF | |
1134 | bool "Perf controller" | |
1135 | depends on PERF_EVENTS | |
1136 | help | |
1137 | This option extends the perf per-cpu mode to restrict monitoring | |
1138 | to threads which belong to the cgroup specified and run on the | |
1139 | designated cpu. | |
1140 | ||
1141 | Say N if unsure. | |
1142 | ||
1143 | config CGROUP_BPF | |
1144 | bool "Support for eBPF programs attached to cgroups" | |
1145 | depends on BPF_SYSCALL | |
1146 | select SOCK_CGROUP_DATA | |
1147 | help | |
1148 | Allow attaching eBPF programs to a cgroup using the bpf(2) | |
1149 | syscall command BPF_PROG_ATTACH. | |
1150 | ||
1151 | In which context these programs are accessed depends on the type | |
1152 | of attachment. For instance, programs that are attached using | |
1153 | BPF_CGROUP_INET_INGRESS will be executed on the ingress path of | |
1154 | inet sockets. | |
1155 | ||
1156 | config CGROUP_DEBUG | |
1157 | bool "Example controller" | |
1158 | default n | |
1159 | help | |
1160 | This option enables a simple controller that exports | |
1161 | debugging information about the cgroups framework. | |
1162 | ||
1163 | Say N. | |
1164 | ||
1165 | config SOCK_CGROUP_DATA | |
1166 | bool | |
1167 | default n | |
1168 | ||
1169 | endif # CGROUPS | |
1170 | ||
1171 | config CHECKPOINT_RESTORE | |
1172 | bool "Checkpoint/restore support" if EXPERT | |
1173 | select PROC_CHILDREN | |
1174 | default n | |
1175 | help | |
1176 | Enables additional kernel features in a sake of checkpoint/restore. | |
1177 | In particular it adds auxiliary prctl codes to setup process text, | |
1178 | data and heap segment sizes, and a few additional /proc filesystem | |
1179 | entries. | |
1180 | ||
1181 | If unsure, say N here. | |
1182 | ||
1183 | menuconfig NAMESPACES | |
1184 | bool "Namespaces support" if EXPERT | |
1185 | depends on MULTIUSER | |
1186 | default !EXPERT | |
1187 | help | |
1188 | Provides the way to make tasks work with different objects using | |
1189 | the same id. For example same IPC id may refer to different objects | |
1190 | or same user id or pid may refer to different tasks when used in | |
1191 | different namespaces. | |
1192 | ||
1193 | if NAMESPACES | |
1194 | ||
1195 | config UTS_NS | |
1196 | bool "UTS namespace" | |
1197 | default y | |
1198 | help | |
1199 | In this namespace tasks see different info provided with the | |
1200 | uname() system call | |
1201 | ||
1202 | config IPC_NS | |
1203 | bool "IPC namespace" | |
1204 | depends on (SYSVIPC || POSIX_MQUEUE) | |
1205 | default y | |
1206 | help | |
1207 | In this namespace tasks work with IPC ids which correspond to | |
1208 | different IPC objects in different namespaces. | |
1209 | ||
1210 | config USER_NS | |
1211 | bool "User namespace" | |
1212 | default n | |
1213 | help | |
1214 | This allows containers, i.e. vservers, to use user namespaces | |
1215 | to provide different user info for different servers. | |
1216 | ||
1217 | When user namespaces are enabled in the kernel it is | |
1218 | recommended that the MEMCG option also be enabled and that | |
1219 | user-space use the memory control groups to limit the amount | |
1220 | of memory a memory unprivileged users can use. | |
1221 | ||
1222 | If unsure, say N. | |
1223 | ||
1224 | config PID_NS | |
1225 | bool "PID Namespaces" | |
1226 | default y | |
1227 | help | |
1228 | Support process id namespaces. This allows having multiple | |
1229 | processes with the same pid as long as they are in different | |
1230 | pid namespaces. This is a building block of containers. | |
1231 | ||
1232 | config NET_NS | |
1233 | bool "Network namespace" | |
1234 | depends on NET | |
1235 | default y | |
1236 | help | |
1237 | Allow user space to create what appear to be multiple instances | |
1238 | of the network stack. | |
1239 | ||
1240 | endif # NAMESPACES | |
1241 | ||
1242 | config SCHED_AUTOGROUP | |
1243 | bool "Automatic process group scheduling" | |
1244 | select CGROUPS | |
1245 | select CGROUP_SCHED | |
1246 | select FAIR_GROUP_SCHED | |
1247 | help | |
1248 | This option optimizes the scheduler for common desktop workloads by | |
1249 | automatically creating and populating task groups. This separation | |
1250 | of workloads isolates aggressive CPU burners (like build jobs) from | |
1251 | desktop applications. Task group autogeneration is currently based | |
1252 | upon task session. | |
1253 | ||
1254 | config SYSFS_DEPRECATED | |
1255 | bool "Enable deprecated sysfs features to support old userspace tools" | |
1256 | depends on SYSFS | |
1257 | default n | |
1258 | help | |
1259 | This option adds code that switches the layout of the "block" class | |
1260 | devices, to not show up in /sys/class/block/, but only in | |
1261 | /sys/block/. | |
1262 | ||
1263 | This switch is only active when the sysfs.deprecated=1 boot option is | |
1264 | passed or the SYSFS_DEPRECATED_V2 option is set. | |
1265 | ||
1266 | This option allows new kernels to run on old distributions and tools, | |
1267 | which might get confused by /sys/class/block/. Since 2007/2008 all | |
1268 | major distributions and tools handle this just fine. | |
1269 | ||
1270 | Recent distributions and userspace tools after 2009/2010 depend on | |
1271 | the existence of /sys/class/block/, and will not work with this | |
1272 | option enabled. | |
1273 | ||
1274 | Only if you are using a new kernel on an old distribution, you might | |
1275 | need to say Y here. | |
1276 | ||
1277 | config SYSFS_DEPRECATED_V2 | |
1278 | bool "Enable deprecated sysfs features by default" | |
1279 | default n | |
1280 | depends on SYSFS | |
1281 | depends on SYSFS_DEPRECATED | |
1282 | help | |
1283 | Enable deprecated sysfs by default. | |
1284 | ||
1285 | See the CONFIG_SYSFS_DEPRECATED option for more details about this | |
1286 | option. | |
1287 | ||
1288 | Only if you are using a new kernel on an old distribution, you might | |
1289 | need to say Y here. Even then, odds are you would not need it | |
1290 | enabled, you can always pass the boot option if absolutely necessary. | |
1291 | ||
1292 | config RELAY | |
1293 | bool "Kernel->user space relay support (formerly relayfs)" | |
1294 | select IRQ_WORK | |
1295 | help | |
1296 | This option enables support for relay interface support in | |
1297 | certain file systems (such as debugfs). | |
1298 | It is designed to provide an efficient mechanism for tools and | |
1299 | facilities to relay large amounts of data from kernel space to | |
1300 | user space. | |
1301 | ||
1302 | If unsure, say N. | |
1303 | ||
1304 | config BLK_DEV_INITRD | |
1305 | bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support" | |
1306 | depends on BROKEN || !FRV | |
1307 | help | |
1308 | The initial RAM filesystem is a ramfs which is loaded by the | |
1309 | boot loader (loadlin or lilo) and that is mounted as root | |
1310 | before the normal boot procedure. It is typically used to | |
1311 | load modules needed to mount the "real" root file system, | |
1312 | etc. See <file:Documentation/admin-guide/initrd.rst> for details. | |
1313 | ||
1314 | If RAM disk support (BLK_DEV_RAM) is also included, this | |
1315 | also enables initial RAM disk (initrd) support and adds | |
1316 | 15 Kbytes (more on some other architectures) to the kernel size. | |
1317 | ||
1318 | If unsure say Y. | |
1319 | ||
1320 | if BLK_DEV_INITRD | |
1321 | ||
1322 | source "usr/Kconfig" | |
1323 | ||
1324 | endif | |
1325 | ||
1326 | choice | |
1327 | prompt "Compiler optimization level" | |
1328 | default CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE | |
1329 | ||
1330 | config CC_OPTIMIZE_FOR_PERFORMANCE | |
1331 | bool "Optimize for performance" | |
1332 | help | |
1333 | This is the default optimization level for the kernel, building | |
1334 | with the "-O2" compiler flag for best performance and most | |
1335 | helpful compile-time warnings. | |
1336 | ||
1337 | config CC_OPTIMIZE_FOR_SIZE | |
1338 | bool "Optimize for size" | |
1339 | help | |
1340 | Enabling this option will pass "-Os" instead of "-O2" to | |
1341 | your compiler resulting in a smaller kernel. | |
1342 | ||
1343 | If unsure, say N. | |
1344 | ||
1345 | endchoice | |
1346 | ||
1347 | config SYSCTL | |
1348 | bool | |
1349 | ||
1350 | config ANON_INODES | |
1351 | bool | |
1352 | ||
1353 | config HAVE_UID16 | |
1354 | bool | |
1355 | ||
1356 | config SYSCTL_EXCEPTION_TRACE | |
1357 | bool | |
1358 | help | |
1359 | Enable support for /proc/sys/debug/exception-trace. | |
1360 | ||
1361 | config SYSCTL_ARCH_UNALIGN_NO_WARN | |
1362 | bool | |
1363 | help | |
1364 | Enable support for /proc/sys/kernel/ignore-unaligned-usertrap | |
1365 | Allows arch to define/use @no_unaligned_warning to possibly warn | |
1366 | about unaligned access emulation going on under the hood. | |
1367 | ||
1368 | config SYSCTL_ARCH_UNALIGN_ALLOW | |
1369 | bool | |
1370 | help | |
1371 | Enable support for /proc/sys/kernel/unaligned-trap | |
1372 | Allows arches to define/use @unaligned_enabled to runtime toggle | |
1373 | the unaligned access emulation. | |
1374 | see arch/parisc/kernel/unaligned.c for reference | |
1375 | ||
1376 | config HAVE_PCSPKR_PLATFORM | |
1377 | bool | |
1378 | ||
1379 | # interpreter that classic socket filters depend on | |
1380 | config BPF | |
1381 | bool | |
1382 | ||
1383 | menuconfig EXPERT | |
1384 | bool "Configure standard kernel features (expert users)" | |
1385 | # Unhide debug options, to make the on-by-default options visible | |
1386 | select DEBUG_KERNEL | |
1387 | help | |
1388 | This option allows certain base kernel options and settings | |
1389 | to be disabled or tweaked. This is for specialized | |
1390 | environments which can tolerate a "non-standard" kernel. | |
1391 | Only use this if you really know what you are doing. | |
1392 | ||
1393 | config UID16 | |
1394 | bool "Enable 16-bit UID system calls" if EXPERT | |
1395 | depends on HAVE_UID16 && MULTIUSER | |
1396 | default y | |
1397 | help | |
1398 | This enables the legacy 16-bit UID syscall wrappers. | |
1399 | ||
1400 | config MULTIUSER | |
1401 | bool "Multiple users, groups and capabilities support" if EXPERT | |
1402 | default y | |
1403 | help | |
1404 | This option enables support for non-root users, groups and | |
1405 | capabilities. | |
1406 | ||
1407 | If you say N here, all processes will run with UID 0, GID 0, and all | |
1408 | possible capabilities. Saying N here also compiles out support for | |
1409 | system calls related to UIDs, GIDs, and capabilities, such as setuid, | |
1410 | setgid, and capset. | |
1411 | ||
1412 | If unsure, say Y here. | |
1413 | ||
1414 | config SGETMASK_SYSCALL | |
1415 | bool "sgetmask/ssetmask syscalls support" if EXPERT | |
1416 | def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH | |
1417 | ---help--- | |
1418 | sys_sgetmask and sys_ssetmask are obsolete system calls | |
1419 | no longer supported in libc but still enabled by default in some | |
1420 | architectures. | |
1421 | ||
1422 | If unsure, leave the default option here. | |
1423 | ||
1424 | config SYSFS_SYSCALL | |
1425 | bool "Sysfs syscall support" if EXPERT | |
1426 | default y | |
1427 | ---help--- | |
1428 | sys_sysfs is an obsolete system call no longer supported in libc. | |
1429 | Note that disabling this option is more secure but might break | |
1430 | compatibility with some systems. | |
1431 | ||
1432 | If unsure say Y here. | |
1433 | ||
1434 | config SYSCTL_SYSCALL | |
1435 | bool "Sysctl syscall support" if EXPERT | |
1436 | depends on PROC_SYSCTL | |
1437 | default n | |
1438 | select SYSCTL | |
1439 | ---help--- | |
1440 | sys_sysctl uses binary paths that have been found challenging | |
1441 | to properly maintain and use. The interface in /proc/sys | |
1442 | using paths with ascii names is now the primary path to this | |
1443 | information. | |
1444 | ||
1445 | Almost nothing using the binary sysctl interface so if you are | |
1446 | trying to save some space it is probably safe to disable this, | |
1447 | making your kernel marginally smaller. | |
1448 | ||
1449 | If unsure say N here. | |
1450 | ||
1451 | config POSIX_TIMERS | |
1452 | bool "Posix Clocks & timers" if EXPERT | |
1453 | default y | |
1454 | help | |
1455 | This includes native support for POSIX timers to the kernel. | |
1456 | Some embedded systems have no use for them and therefore they | |
1457 | can be configured out to reduce the size of the kernel image. | |
1458 | ||
1459 | When this option is disabled, the following syscalls won't be | |
1460 | available: timer_create, timer_gettime: timer_getoverrun, | |
1461 | timer_settime, timer_delete, clock_adjtime, getitimer, | |
1462 | setitimer, alarm. Furthermore, the clock_settime, clock_gettime, | |
1463 | clock_getres and clock_nanosleep syscalls will be limited to | |
1464 | CLOCK_REALTIME, CLOCK_MONOTONIC and CLOCK_BOOTTIME only. | |
1465 | ||
1466 | If unsure say y. | |
1467 | ||
1468 | config KALLSYMS | |
1469 | bool "Load all symbols for debugging/ksymoops" if EXPERT | |
1470 | default y | |
1471 | help | |
1472 | Say Y here to let the kernel print out symbolic crash information and | |
1473 | symbolic stack backtraces. This increases the size of the kernel | |
1474 | somewhat, as all symbols have to be loaded into the kernel image. | |
1475 | ||
1476 | config KALLSYMS_ALL | |
1477 | bool "Include all symbols in kallsyms" | |
1478 | depends on DEBUG_KERNEL && KALLSYMS | |
1479 | help | |
1480 | Normally kallsyms only contains the symbols of functions for nicer | |
1481 | OOPS messages and backtraces (i.e., symbols from the text and inittext | |
1482 | sections). This is sufficient for most cases. And only in very rare | |
1483 | cases (e.g., when a debugger is used) all symbols are required (e.g., | |
1484 | names of variables from the data sections, etc). | |
1485 | ||
1486 | This option makes sure that all symbols are loaded into the kernel | |
1487 | image (i.e., symbols from all sections) in cost of increased kernel | |
1488 | size (depending on the kernel configuration, it may be 300KiB or | |
1489 | something like this). | |
1490 | ||
1491 | Say N unless you really need all symbols. | |
1492 | ||
1493 | config KALLSYMS_ABSOLUTE_PERCPU | |
1494 | bool | |
1495 | depends on KALLSYMS | |
1496 | default X86_64 && SMP | |
1497 | ||
1498 | config KALLSYMS_BASE_RELATIVE | |
1499 | bool | |
1500 | depends on KALLSYMS | |
1501 | default !IA64 && !(TILE && 64BIT) | |
1502 | help | |
1503 | Instead of emitting them as absolute values in the native word size, | |
1504 | emit the symbol references in the kallsyms table as 32-bit entries, | |
1505 | each containing a relative value in the range [base, base + U32_MAX] | |
1506 | or, when KALLSYMS_ABSOLUTE_PERCPU is in effect, each containing either | |
1507 | an absolute value in the range [0, S32_MAX] or a relative value in the | |
1508 | range [base, base + S32_MAX], where base is the lowest relative symbol | |
1509 | address encountered in the image. | |
1510 | ||
1511 | On 64-bit builds, this reduces the size of the address table by 50%, | |
1512 | but more importantly, it results in entries whose values are build | |
1513 | time constants, and no relocation pass is required at runtime to fix | |
1514 | up the entries based on the runtime load address of the kernel. | |
1515 | ||
1516 | config PRINTK | |
1517 | default y | |
1518 | bool "Enable support for printk" if EXPERT | |
1519 | select IRQ_WORK | |
1520 | help | |
1521 | This option enables normal printk support. Removing it | |
1522 | eliminates most of the message strings from the kernel image | |
1523 | and makes the kernel more or less silent. As this makes it | |
1524 | very difficult to diagnose system problems, saying N here is | |
1525 | strongly discouraged. | |
1526 | ||
1527 | config PRINTK_NMI | |
1528 | def_bool y | |
1529 | depends on PRINTK | |
1530 | depends on HAVE_NMI | |
1531 | ||
1532 | config BUG | |
1533 | bool "BUG() support" if EXPERT | |
1534 | default y | |
1535 | help | |
1536 | Disabling this option eliminates support for BUG and WARN, reducing | |
1537 | the size of your kernel image and potentially quietly ignoring | |
1538 | numerous fatal conditions. You should only consider disabling this | |
1539 | option for embedded systems with no facilities for reporting errors. | |
1540 | Just say Y. | |
1541 | ||
1542 | config ELF_CORE | |
1543 | depends on COREDUMP | |
1544 | default y | |
1545 | bool "Enable ELF core dumps" if EXPERT | |
1546 | help | |
1547 | Enable support for generating core dumps. Disabling saves about 4k. | |
1548 | ||
1549 | ||
1550 | config PCSPKR_PLATFORM | |
1551 | bool "Enable PC-Speaker support" if EXPERT | |
1552 | depends on HAVE_PCSPKR_PLATFORM | |
1553 | select I8253_LOCK | |
1554 | default y | |
1555 | help | |
1556 | This option allows to disable the internal PC-Speaker | |
1557 | support, saving some memory. | |
1558 | ||
1559 | config BASE_FULL | |
1560 | default y | |
1561 | bool "Enable full-sized data structures for core" if EXPERT | |
1562 | help | |
1563 | Disabling this option reduces the size of miscellaneous core | |
1564 | kernel data structures. This saves memory on small machines, | |
1565 | but may reduce performance. | |
1566 | ||
1567 | config FUTEX | |
1568 | bool "Enable futex support" if EXPERT | |
1569 | default y | |
1570 | select RT_MUTEXES | |
1571 | help | |
1572 | Disabling this option will cause the kernel to be built without | |
1573 | support for "fast userspace mutexes". The resulting kernel may not | |
1574 | run glibc-based applications correctly. | |
1575 | ||
1576 | config HAVE_FUTEX_CMPXCHG | |
1577 | bool | |
1578 | depends on FUTEX | |
1579 | help | |
1580 | Architectures should select this if futex_atomic_cmpxchg_inatomic() | |
1581 | is implemented and always working. This removes a couple of runtime | |
1582 | checks. | |
1583 | ||
1584 | config EPOLL | |
1585 | bool "Enable eventpoll support" if EXPERT | |
1586 | default y | |
1587 | select ANON_INODES | |
1588 | help | |
1589 | Disabling this option will cause the kernel to be built without | |
1590 | support for epoll family of system calls. | |
1591 | ||
1592 | config SIGNALFD | |
1593 | bool "Enable signalfd() system call" if EXPERT | |
1594 | select ANON_INODES | |
1595 | default y | |
1596 | help | |
1597 | Enable the signalfd() system call that allows to receive signals | |
1598 | on a file descriptor. | |
1599 | ||
1600 | If unsure, say Y. | |
1601 | ||
1602 | config TIMERFD | |
1603 | bool "Enable timerfd() system call" if EXPERT | |
1604 | select ANON_INODES | |
1605 | default y | |
1606 | help | |
1607 | Enable the timerfd() system call that allows to receive timer | |
1608 | events on a file descriptor. | |
1609 | ||
1610 | If unsure, say Y. | |
1611 | ||
1612 | config EVENTFD | |
1613 | bool "Enable eventfd() system call" if EXPERT | |
1614 | select ANON_INODES | |
1615 | default y | |
1616 | help | |
1617 | Enable the eventfd() system call that allows to receive both | |
1618 | kernel notification (ie. KAIO) or userspace notifications. | |
1619 | ||
1620 | If unsure, say Y. | |
1621 | ||
1622 | # syscall, maps, verifier | |
1623 | config BPF_SYSCALL | |
1624 | bool "Enable bpf() system call" | |
1625 | select ANON_INODES | |
1626 | select BPF | |
1627 | default n | |
1628 | help | |
1629 | Enable the bpf() system call that allows to manipulate eBPF | |
1630 | programs and maps via file descriptors. | |
1631 | ||
1632 | config SHMEM | |
1633 | bool "Use full shmem filesystem" if EXPERT | |
1634 | default y | |
1635 | depends on MMU | |
1636 | help | |
1637 | The shmem is an internal filesystem used to manage shared memory. | |
1638 | It is backed by swap and manages resource limits. It is also exported | |
1639 | to userspace as tmpfs if TMPFS is enabled. Disabling this | |
1640 | option replaces shmem and tmpfs with the much simpler ramfs code, | |
1641 | which may be appropriate on small systems without swap. | |
1642 | ||
1643 | config AIO | |
1644 | bool "Enable AIO support" if EXPERT | |
1645 | default y | |
1646 | help | |
1647 | This option enables POSIX asynchronous I/O which may by used | |
1648 | by some high performance threaded applications. Disabling | |
1649 | this option saves about 7k. | |
1650 | ||
1651 | config ADVISE_SYSCALLS | |
1652 | bool "Enable madvise/fadvise syscalls" if EXPERT | |
1653 | default y | |
1654 | help | |
1655 | This option enables the madvise and fadvise syscalls, used by | |
1656 | applications to advise the kernel about their future memory or file | |
1657 | usage, improving performance. If building an embedded system where no | |
1658 | applications use these syscalls, you can disable this option to save | |
1659 | space. | |
1660 | ||
1661 | config USERFAULTFD | |
1662 | bool "Enable userfaultfd() system call" | |
1663 | select ANON_INODES | |
1664 | depends on MMU | |
1665 | help | |
1666 | Enable the userfaultfd() system call that allows to intercept and | |
1667 | handle page faults in userland. | |
1668 | ||
1669 | config PCI_QUIRKS | |
1670 | default y | |
1671 | bool "Enable PCI quirk workarounds" if EXPERT | |
1672 | depends on PCI | |
1673 | help | |
1674 | This enables workarounds for various PCI chipset | |
1675 | bugs/quirks. Disable this only if your target machine is | |
1676 | unaffected by PCI quirks. | |
1677 | ||
1678 | config MEMBARRIER | |
1679 | bool "Enable membarrier() system call" if EXPERT | |
1680 | default y | |
1681 | help | |
1682 | Enable the membarrier() system call that allows issuing memory | |
1683 | barriers across all running threads, which can be used to distribute | |
1684 | the cost of user-space memory barriers asymmetrically by transforming | |
1685 | pairs of memory barriers into pairs consisting of membarrier() and a | |
1686 | compiler barrier. | |
1687 | ||
1688 | If unsure, say Y. | |
1689 | ||
1690 | config EMBEDDED | |
1691 | bool "Embedded system" | |
1692 | option allnoconfig_y | |
1693 | select EXPERT | |
1694 | help | |
1695 | This option should be enabled if compiling the kernel for | |
1696 | an embedded system so certain expert options are available | |
1697 | for configuration. | |
1698 | ||
1699 | config HAVE_PERF_EVENTS | |
1700 | bool | |
1701 | help | |
1702 | See tools/perf/design.txt for details. | |
1703 | ||
1704 | config PERF_USE_VMALLOC | |
1705 | bool | |
1706 | help | |
1707 | See tools/perf/design.txt for details | |
1708 | ||
1709 | config PC104 | |
1710 | bool "PC/104 support" | |
1711 | help | |
1712 | Expose PC/104 form factor device drivers and options available for | |
1713 | selection and configuration. Enable this option if your target | |
1714 | machine has a PC/104 bus. | |
1715 | ||
1716 | menu "Kernel Performance Events And Counters" | |
1717 | ||
1718 | config PERF_EVENTS | |
1719 | bool "Kernel performance events and counters" | |
1720 | default y if PROFILING | |
1721 | depends on HAVE_PERF_EVENTS | |
1722 | select ANON_INODES | |
1723 | select IRQ_WORK | |
1724 | select SRCU | |
1725 | help | |
1726 | Enable kernel support for various performance events provided | |
1727 | by software and hardware. | |
1728 | ||
1729 | Software events are supported either built-in or via the | |
1730 | use of generic tracepoints. | |
1731 | ||
1732 | Most modern CPUs support performance events via performance | |
1733 | counter registers. These registers count the number of certain | |
1734 | types of hw events: such as instructions executed, cachemisses | |
1735 | suffered, or branches mis-predicted - without slowing down the | |
1736 | kernel or applications. These registers can also trigger interrupts | |
1737 | when a threshold number of events have passed - and can thus be | |
1738 | used to profile the code that runs on that CPU. | |
1739 | ||
1740 | The Linux Performance Event subsystem provides an abstraction of | |
1741 | these software and hardware event capabilities, available via a | |
1742 | system call and used by the "perf" utility in tools/perf/. It | |
1743 | provides per task and per CPU counters, and it provides event | |
1744 | capabilities on top of those. | |
1745 | ||
1746 | Say Y if unsure. | |
1747 | ||
1748 | config DEBUG_PERF_USE_VMALLOC | |
1749 | default n | |
1750 | bool "Debug: use vmalloc to back perf mmap() buffers" | |
1751 | depends on PERF_EVENTS && DEBUG_KERNEL && !PPC | |
1752 | select PERF_USE_VMALLOC | |
1753 | help | |
1754 | Use vmalloc memory to back perf mmap() buffers. | |
1755 | ||
1756 | Mostly useful for debugging the vmalloc code on platforms | |
1757 | that don't require it. | |
1758 | ||
1759 | Say N if unsure. | |
1760 | ||
1761 | endmenu | |
1762 | ||
1763 | config VM_EVENT_COUNTERS | |
1764 | default y | |
1765 | bool "Enable VM event counters for /proc/vmstat" if EXPERT | |
1766 | help | |
1767 | VM event counters are needed for event counts to be shown. | |
1768 | This option allows the disabling of the VM event counters | |
1769 | on EXPERT systems. /proc/vmstat will only show page counts | |
1770 | if VM event counters are disabled. | |
1771 | ||
1772 | config SLUB_DEBUG | |
1773 | default y | |
1774 | bool "Enable SLUB debugging support" if EXPERT | |
1775 | depends on SLUB && SYSFS | |
1776 | help | |
1777 | SLUB has extensive debug support features. Disabling these can | |
1778 | result in significant savings in code size. This also disables | |
1779 | SLUB sysfs support. /sys/slab will not exist and there will be | |
1780 | no support for cache validation etc. | |
1781 | ||
1782 | config SLUB_MEMCG_SYSFS_ON | |
1783 | default n | |
1784 | bool "Enable memcg SLUB sysfs support by default" if EXPERT | |
1785 | depends on SLUB && SYSFS && MEMCG | |
1786 | help | |
1787 | SLUB creates a directory under /sys/kernel/slab for each | |
1788 | allocation cache to host info and debug files. If memory | |
1789 | cgroup is enabled, each cache can have per memory cgroup | |
1790 | caches. SLUB can create the same sysfs directories for these | |
1791 | caches under /sys/kernel/slab/CACHE/cgroup but it can lead | |
1792 | to a very high number of debug files being created. This is | |
1793 | controlled by slub_memcg_sysfs boot parameter and this | |
1794 | config option determines the parameter's default value. | |
1795 | ||
1796 | config COMPAT_BRK | |
1797 | bool "Disable heap randomization" | |
1798 | default y | |
1799 | help | |
1800 | Randomizing heap placement makes heap exploits harder, but it | |
1801 | also breaks ancient binaries (including anything libc5 based). | |
1802 | This option changes the bootup default to heap randomization | |
1803 | disabled, and can be overridden at runtime by setting | |
1804 | /proc/sys/kernel/randomize_va_space to 2. | |
1805 | ||
1806 | On non-ancient distros (post-2000 ones) N is usually a safe choice. | |
1807 | ||
1808 | choice | |
1809 | prompt "Choose SLAB allocator" | |
1810 | default SLUB | |
1811 | help | |
1812 | This option allows to select a slab allocator. | |
1813 | ||
1814 | config SLAB | |
1815 | bool "SLAB" | |
1816 | select HAVE_HARDENED_USERCOPY_ALLOCATOR | |
1817 | help | |
1818 | The regular slab allocator that is established and known to work | |
1819 | well in all environments. It organizes cache hot objects in | |
1820 | per cpu and per node queues. | |
1821 | ||
1822 | config SLUB | |
1823 | bool "SLUB (Unqueued Allocator)" | |
1824 | select HAVE_HARDENED_USERCOPY_ALLOCATOR | |
1825 | help | |
1826 | SLUB is a slab allocator that minimizes cache line usage | |
1827 | instead of managing queues of cached objects (SLAB approach). | |
1828 | Per cpu caching is realized using slabs of objects instead | |
1829 | of queues of objects. SLUB can use memory efficiently | |
1830 | and has enhanced diagnostics. SLUB is the default choice for | |
1831 | a slab allocator. | |
1832 | ||
1833 | config SLOB | |
1834 | depends on EXPERT | |
1835 | bool "SLOB (Simple Allocator)" | |
1836 | help | |
1837 | SLOB replaces the stock allocator with a drastically simpler | |
1838 | allocator. SLOB is generally more space efficient but | |
1839 | does not perform as well on large systems. | |
1840 | ||
1841 | endchoice | |
1842 | ||
1843 | config SLAB_FREELIST_RANDOM | |
1844 | default n | |
1845 | depends on SLAB || SLUB | |
1846 | bool "SLAB freelist randomization" | |
1847 | help | |
1848 | Randomizes the freelist order used on creating new pages. This | |
1849 | security feature reduces the predictability of the kernel slab | |
1850 | allocator against heap overflows. | |
1851 | ||
1852 | config SLUB_CPU_PARTIAL | |
1853 | default y | |
1854 | depends on SLUB && SMP | |
1855 | bool "SLUB per cpu partial cache" | |
1856 | help | |
1857 | Per cpu partial caches accellerate objects allocation and freeing | |
1858 | that is local to a processor at the price of more indeterminism | |
1859 | in the latency of the free. On overflow these caches will be cleared | |
1860 | which requires the taking of locks that may cause latency spikes. | |
1861 | Typically one would choose no for a realtime system. | |
1862 | ||
1863 | config MMAP_ALLOW_UNINITIALIZED | |
1864 | bool "Allow mmapped anonymous memory to be uninitialized" | |
1865 | depends on EXPERT && !MMU | |
1866 | default n | |
1867 | help | |
1868 | Normally, and according to the Linux spec, anonymous memory obtained | |
1869 | from mmap() has it's contents cleared before it is passed to | |
1870 | userspace. Enabling this config option allows you to request that | |
1871 | mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus | |
1872 | providing a huge performance boost. If this option is not enabled, | |
1873 | then the flag will be ignored. | |
1874 | ||
1875 | This is taken advantage of by uClibc's malloc(), and also by | |
1876 | ELF-FDPIC binfmt's brk and stack allocator. | |
1877 | ||
1878 | Because of the obvious security issues, this option should only be | |
1879 | enabled on embedded devices where you control what is run in | |
1880 | userspace. Since that isn't generally a problem on no-MMU systems, | |
1881 | it is normally safe to say Y here. | |
1882 | ||
1883 | See Documentation/nommu-mmap.txt for more information. | |
1884 | ||
1885 | config SYSTEM_DATA_VERIFICATION | |
1886 | def_bool n | |
1887 | select SYSTEM_TRUSTED_KEYRING | |
1888 | select KEYS | |
1889 | select CRYPTO | |
1890 | select CRYPTO_RSA | |
1891 | select ASYMMETRIC_KEY_TYPE | |
1892 | select ASYMMETRIC_PUBLIC_KEY_SUBTYPE | |
1893 | select ASN1 | |
1894 | select OID_REGISTRY | |
1895 | select X509_CERTIFICATE_PARSER | |
1896 | select PKCS7_MESSAGE_PARSER | |
1897 | help | |
1898 | Provide PKCS#7 message verification using the contents of the system | |
1899 | trusted keyring to provide public keys. This then can be used for | |
1900 | module verification, kexec image verification and firmware blob | |
1901 | verification. | |
1902 | ||
1903 | config PROFILING | |
1904 | bool "Profiling support" | |
1905 | help | |
1906 | Say Y here to enable the extended profiling support mechanisms used | |
1907 | by profilers such as OProfile. | |
1908 | ||
1909 | # | |
1910 | # Place an empty function call at each tracepoint site. Can be | |
1911 | # dynamically changed for a probe function. | |
1912 | # | |
1913 | config TRACEPOINTS | |
1914 | bool | |
1915 | ||
1916 | source "arch/Kconfig" | |
1917 | ||
1918 | endmenu # General setup | |
1919 | ||
1920 | config HAVE_GENERIC_DMA_COHERENT | |
1921 | bool | |
1922 | default n | |
1923 | ||
1924 | config SLABINFO | |
1925 | bool | |
1926 | depends on PROC_FS | |
1927 | depends on SLAB || SLUB_DEBUG | |
1928 | default y | |
1929 | ||
1930 | config RT_MUTEXES | |
1931 | bool | |
1932 | ||
1933 | config BASE_SMALL | |
1934 | int | |
1935 | default 0 if BASE_FULL | |
1936 | default 1 if !BASE_FULL | |
1937 | ||
1938 | menuconfig MODULES | |
1939 | bool "Enable loadable module support" | |
1940 | option modules | |
1941 | help | |
1942 | Kernel modules are small pieces of compiled code which can | |
1943 | be inserted in the running kernel, rather than being | |
1944 | permanently built into the kernel. You use the "modprobe" | |
1945 | tool to add (and sometimes remove) them. If you say Y here, | |
1946 | many parts of the kernel can be built as modules (by | |
1947 | answering M instead of Y where indicated): this is most | |
1948 | useful for infrequently used options which are not required | |
1949 | for booting. For more information, see the man pages for | |
1950 | modprobe, lsmod, modinfo, insmod and rmmod. | |
1951 | ||
1952 | If you say Y here, you will need to run "make | |
1953 | modules_install" to put the modules under /lib/modules/ | |
1954 | where modprobe can find them (you may need to be root to do | |
1955 | this). | |
1956 | ||
1957 | If unsure, say Y. | |
1958 | ||
1959 | if MODULES | |
1960 | ||
1961 | config MODULE_FORCE_LOAD | |
1962 | bool "Forced module loading" | |
1963 | default n | |
1964 | help | |
1965 | Allow loading of modules without version information (ie. modprobe | |
1966 | --force). Forced module loading sets the 'F' (forced) taint flag and | |
1967 | is usually a really bad idea. | |
1968 | ||
1969 | config MODULE_UNLOAD | |
1970 | bool "Module unloading" | |
1971 | help | |
1972 | Without this option you will not be able to unload any | |
1973 | modules (note that some modules may not be unloadable | |
1974 | anyway), which makes your kernel smaller, faster | |
1975 | and simpler. If unsure, say Y. | |
1976 | ||
1977 | config MODULE_FORCE_UNLOAD | |
1978 | bool "Forced module unloading" | |
1979 | depends on MODULE_UNLOAD | |
1980 | help | |
1981 | This option allows you to force a module to unload, even if the | |
1982 | kernel believes it is unsafe: the kernel will remove the module | |
1983 | without waiting for anyone to stop using it (using the -f option to | |
1984 | rmmod). This is mainly for kernel developers and desperate users. | |
1985 | If unsure, say N. | |
1986 | ||
1987 | config MODVERSIONS | |
1988 | bool "Module versioning support" | |
1989 | help | |
1990 | Usually, you have to use modules compiled with your kernel. | |
1991 | Saying Y here makes it sometimes possible to use modules | |
1992 | compiled for different kernels, by adding enough information | |
1993 | to the modules to (hopefully) spot any changes which would | |
1994 | make them incompatible with the kernel you are running. If | |
1995 | unsure, say N. | |
1996 | ||
1997 | config MODULE_REL_CRCS | |
1998 | bool | |
1999 | depends on MODVERSIONS | |
2000 | ||
2001 | config MODULE_SRCVERSION_ALL | |
2002 | bool "Source checksum for all modules" | |
2003 | help | |
2004 | Modules which contain a MODULE_VERSION get an extra "srcversion" | |
2005 | field inserted into their modinfo section, which contains a | |
2006 | sum of the source files which made it. This helps maintainers | |
2007 | see exactly which source was used to build a module (since | |
2008 | others sometimes change the module source without updating | |
2009 | the version). With this option, such a "srcversion" field | |
2010 | will be created for all modules. If unsure, say N. | |
2011 | ||
2012 | config MODULE_SIG | |
2013 | bool "Module signature verification" | |
2014 | depends on MODULES | |
2015 | select SYSTEM_DATA_VERIFICATION | |
2016 | help | |
2017 | Check modules for valid signatures upon load: the signature | |
2018 | is simply appended to the module. For more information see | |
2019 | Documentation/module-signing.txt. | |
2020 | ||
2021 | Note that this option adds the OpenSSL development packages as a | |
2022 | kernel build dependency so that the signing tool can use its crypto | |
2023 | library. | |
2024 | ||
2025 | !!!WARNING!!! If you enable this option, you MUST make sure that the | |
2026 | module DOES NOT get stripped after being signed. This includes the | |
2027 | debuginfo strip done by some packagers (such as rpmbuild) and | |
2028 | inclusion into an initramfs that wants the module size reduced. | |
2029 | ||
2030 | config MODULE_SIG_FORCE | |
2031 | bool "Require modules to be validly signed" | |
2032 | depends on MODULE_SIG | |
2033 | help | |
2034 | Reject unsigned modules or signed modules for which we don't have a | |
2035 | key. Without this, such modules will simply taint the kernel. | |
2036 | ||
2037 | config MODULE_SIG_ALL | |
2038 | bool "Automatically sign all modules" | |
2039 | default y | |
2040 | depends on MODULE_SIG | |
2041 | help | |
2042 | Sign all modules during make modules_install. Without this option, | |
2043 | modules must be signed manually, using the scripts/sign-file tool. | |
2044 | ||
2045 | comment "Do not forget to sign required modules with scripts/sign-file" | |
2046 | depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL | |
2047 | ||
2048 | choice | |
2049 | prompt "Which hash algorithm should modules be signed with?" | |
2050 | depends on MODULE_SIG | |
2051 | help | |
2052 | This determines which sort of hashing algorithm will be used during | |
2053 | signature generation. This algorithm _must_ be built into the kernel | |
2054 | directly so that signature verification can take place. It is not | |
2055 | possible to load a signed module containing the algorithm to check | |
2056 | the signature on that module. | |
2057 | ||
2058 | config MODULE_SIG_SHA1 | |
2059 | bool "Sign modules with SHA-1" | |
2060 | select CRYPTO_SHA1 | |
2061 | ||
2062 | config MODULE_SIG_SHA224 | |
2063 | bool "Sign modules with SHA-224" | |
2064 | select CRYPTO_SHA256 | |
2065 | ||
2066 | config MODULE_SIG_SHA256 | |
2067 | bool "Sign modules with SHA-256" | |
2068 | select CRYPTO_SHA256 | |
2069 | ||
2070 | config MODULE_SIG_SHA384 | |
2071 | bool "Sign modules with SHA-384" | |
2072 | select CRYPTO_SHA512 | |
2073 | ||
2074 | config MODULE_SIG_SHA512 | |
2075 | bool "Sign modules with SHA-512" | |
2076 | select CRYPTO_SHA512 | |
2077 | ||
2078 | endchoice | |
2079 | ||
2080 | config MODULE_SIG_HASH | |
2081 | string | |
2082 | depends on MODULE_SIG | |
2083 | default "sha1" if MODULE_SIG_SHA1 | |
2084 | default "sha224" if MODULE_SIG_SHA224 | |
2085 | default "sha256" if MODULE_SIG_SHA256 | |
2086 | default "sha384" if MODULE_SIG_SHA384 | |
2087 | default "sha512" if MODULE_SIG_SHA512 | |
2088 | ||
2089 | config MODULE_COMPRESS | |
2090 | bool "Compress modules on installation" | |
2091 | depends on MODULES | |
2092 | help | |
2093 | ||
2094 | Compresses kernel modules when 'make modules_install' is run; gzip or | |
2095 | xz depending on "Compression algorithm" below. | |
2096 | ||
2097 | module-init-tools MAY support gzip, and kmod MAY support gzip and xz. | |
2098 | ||
2099 | Out-of-tree kernel modules installed using Kbuild will also be | |
2100 | compressed upon installation. | |
2101 | ||
2102 | Note: for modules inside an initrd or initramfs, it's more efficient | |
2103 | to compress the whole initrd or initramfs instead. | |
2104 | ||
2105 | Note: This is fully compatible with signed modules. | |
2106 | ||
2107 | If in doubt, say N. | |
2108 | ||
2109 | choice | |
2110 | prompt "Compression algorithm" | |
2111 | depends on MODULE_COMPRESS | |
2112 | default MODULE_COMPRESS_GZIP | |
2113 | help | |
2114 | This determines which sort of compression will be used during | |
2115 | 'make modules_install'. | |
2116 | ||
2117 | GZIP (default) and XZ are supported. | |
2118 | ||
2119 | config MODULE_COMPRESS_GZIP | |
2120 | bool "GZIP" | |
2121 | ||
2122 | config MODULE_COMPRESS_XZ | |
2123 | bool "XZ" | |
2124 | ||
2125 | endchoice | |
2126 | ||
2127 | config TRIM_UNUSED_KSYMS | |
2128 | bool "Trim unused exported kernel symbols" | |
2129 | depends on MODULES && !UNUSED_SYMBOLS | |
2130 | help | |
2131 | The kernel and some modules make many symbols available for | |
2132 | other modules to use via EXPORT_SYMBOL() and variants. Depending | |
2133 | on the set of modules being selected in your kernel configuration, | |
2134 | many of those exported symbols might never be used. | |
2135 | ||
2136 | This option allows for unused exported symbols to be dropped from | |
2137 | the build. In turn, this provides the compiler more opportunities | |
2138 | (especially when using LTO) for optimizing the code and reducing | |
2139 | binary size. This might have some security advantages as well. | |
2140 | ||
2141 | If unsure, or if you need to build out-of-tree modules, say N. | |
2142 | ||
2143 | endif # MODULES | |
2144 | ||
2145 | config MODULES_TREE_LOOKUP | |
2146 | def_bool y | |
2147 | depends on PERF_EVENTS || TRACING | |
2148 | ||
2149 | config INIT_ALL_POSSIBLE | |
2150 | bool | |
2151 | help | |
2152 | Back when each arch used to define their own cpu_online_mask and | |
2153 | cpu_possible_mask, some of them chose to initialize cpu_possible_mask | |
2154 | with all 1s, and others with all 0s. When they were centralised, | |
2155 | it was better to provide this option than to break all the archs | |
2156 | and have several arch maintainers pursuing me down dark alleys. | |
2157 | ||
2158 | source "block/Kconfig" | |
2159 | ||
2160 | config PREEMPT_NOTIFIERS | |
2161 | bool | |
2162 | ||
2163 | config PADATA | |
2164 | depends on SMP | |
2165 | bool | |
2166 | ||
2167 | config ASN1 | |
2168 | tristate | |
2169 | help | |
2170 | Build a simple ASN.1 grammar compiler that produces a bytecode output | |
2171 | that can be interpreted by the ASN.1 stream decoder and used to | |
2172 | inform it as to what tags are to be expected in a stream and what | |
2173 | functions to call on what tags. | |
2174 | ||
2175 | source "kernel/Kconfig.locks" |