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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 menu "General setup"
30
31 config BROKEN
32 bool
33
34 config BROKEN_ON_SMP
35 bool
36 depends on BROKEN || !SMP
37 default y
38
39 config INIT_ENV_ARG_LIMIT
40 int
41 default 32 if !UML
42 default 128 if UML
43 help
44 Maximum of each of the number of arguments and environment
45 variables passed to init from the kernel command line.
46
47
48 config CROSS_COMPILE
49 string "Cross-compiler tool prefix"
50 help
51 Same as running 'make CROSS_COMPILE=prefix-' but stored for
52 default make runs in this kernel build directory. You don't
53 need to set this unless you want the configured kernel build
54 directory to select the cross-compiler automatically.
55
56 config LOCALVERSION
57 string "Local version - append to kernel release"
58 help
59 Append an extra string to the end of your kernel version.
60 This will show up when you type uname, for example.
61 The string you set here will be appended after the contents of
62 any files with a filename matching localversion* in your
63 object and source tree, in that order. Your total string can
64 be a maximum of 64 characters.
65
66 config LOCALVERSION_AUTO
67 bool "Automatically append version information to the version string"
68 default y
69 help
70 This will try to automatically determine if the current tree is a
71 release tree by looking for git tags that belong to the current
72 top of tree revision.
73
74 A string of the format -gxxxxxxxx will be added to the localversion
75 if a git-based tree is found. The string generated by this will be
76 appended after any matching localversion* files, and after the value
77 set in CONFIG_LOCALVERSION.
78
79 (The actual string used here is the first eight characters produced
80 by running the command:
81
82 $ git rev-parse --verify HEAD
83
84 which is done within the script "scripts/setlocalversion".)
85
86 config HAVE_KERNEL_GZIP
87 bool
88
89 config HAVE_KERNEL_BZIP2
90 bool
91
92 config HAVE_KERNEL_LZMA
93 bool
94
95 config HAVE_KERNEL_XZ
96 bool
97
98 config HAVE_KERNEL_LZO
99 bool
100
101 choice
102 prompt "Kernel compression mode"
103 default KERNEL_GZIP
104 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
105 help
106 The linux kernel is a kind of self-extracting executable.
107 Several compression algorithms are available, which differ
108 in efficiency, compression and decompression speed.
109 Compression speed is only relevant when building a kernel.
110 Decompression speed is relevant at each boot.
111
112 If you have any problems with bzip2 or lzma compressed
113 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
114 version of this functionality (bzip2 only), for 2.4, was
115 supplied by Christian Ludwig)
116
117 High compression options are mostly useful for users, who
118 are low on disk space (embedded systems), but for whom ram
119 size matters less.
120
121 If in doubt, select 'gzip'
122
123 config KERNEL_GZIP
124 bool "Gzip"
125 depends on HAVE_KERNEL_GZIP
126 help
127 The old and tried gzip compression. It provides a good balance
128 between compression ratio and decompression speed.
129
130 config KERNEL_BZIP2
131 bool "Bzip2"
132 depends on HAVE_KERNEL_BZIP2
133 help
134 Its compression ratio and speed is intermediate.
135 Decompression speed is slowest among the choices. The kernel
136 size is about 10% smaller with bzip2, in comparison to gzip.
137 Bzip2 uses a large amount of memory. For modern kernels you
138 will need at least 8MB RAM or more for booting.
139
140 config KERNEL_LZMA
141 bool "LZMA"
142 depends on HAVE_KERNEL_LZMA
143 help
144 This compression algorithm's ratio is best. Decompression speed
145 is between gzip and bzip2. Compression is slowest.
146 The kernel size is about 33% smaller with LZMA in comparison to gzip.
147
148 config KERNEL_XZ
149 bool "XZ"
150 depends on HAVE_KERNEL_XZ
151 help
152 XZ uses the LZMA2 algorithm and instruction set specific
153 BCJ filters which can improve compression ratio of executable
154 code. The size of the kernel is about 30% smaller with XZ in
155 comparison to gzip. On architectures for which there is a BCJ
156 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
157 will create a few percent smaller kernel than plain LZMA.
158
159 The speed is about the same as with LZMA: The decompression
160 speed of XZ is better than that of bzip2 but worse than gzip
161 and LZO. Compression is slow.
162
163 config KERNEL_LZO
164 bool "LZO"
165 depends on HAVE_KERNEL_LZO
166 help
167 Its compression ratio is the poorest among the choices. The kernel
168 size is about 10% bigger than gzip; however its speed
169 (both compression and decompression) is the fastest.
170
171 endchoice
172
173 config DEFAULT_HOSTNAME
174 string "Default hostname"
175 default "(none)"
176 help
177 This option determines the default system hostname before userspace
178 calls sethostname(2). The kernel traditionally uses "(none)" here,
179 but you may wish to use a different default here to make a minimal
180 system more usable with less configuration.
181
182 config SWAP
183 bool "Support for paging of anonymous memory (swap)"
184 depends on MMU && BLOCK
185 default y
186 help
187 This option allows you to choose whether you want to have support
188 for so called swap devices or swap files in your kernel that are
189 used to provide more virtual memory than the actual RAM present
190 in your computer. If unsure say Y.
191
192 config SYSVIPC
193 bool "System V IPC"
194 ---help---
195 Inter Process Communication is a suite of library functions and
196 system calls which let processes (running programs) synchronize and
197 exchange information. It is generally considered to be a good thing,
198 and some programs won't run unless you say Y here. In particular, if
199 you want to run the DOS emulator dosemu under Linux (read the
200 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
201 you'll need to say Y here.
202
203 You can find documentation about IPC with "info ipc" and also in
204 section 6.4 of the Linux Programmer's Guide, available from
205 <http://www.tldp.org/guides.html>.
206
207 config SYSVIPC_SYSCTL
208 bool
209 depends on SYSVIPC
210 depends on SYSCTL
211 default y
212
213 config POSIX_MQUEUE
214 bool "POSIX Message Queues"
215 depends on NET
216 ---help---
217 POSIX variant of message queues is a part of IPC. In POSIX message
218 queues every message has a priority which decides about succession
219 of receiving it by a process. If you want to compile and run
220 programs written e.g. for Solaris with use of its POSIX message
221 queues (functions mq_*) say Y here.
222
223 POSIX message queues are visible as a filesystem called 'mqueue'
224 and can be mounted somewhere if you want to do filesystem
225 operations on message queues.
226
227 If unsure, say Y.
228
229 config POSIX_MQUEUE_SYSCTL
230 bool
231 depends on POSIX_MQUEUE
232 depends on SYSCTL
233 default y
234
235 config FHANDLE
236 bool "open by fhandle syscalls"
237 select EXPORTFS
238 help
239 If you say Y here, a user level program will be able to map
240 file names to handle and then later use the handle for
241 different file system operations. This is useful in implementing
242 userspace file servers, which now track files using handles instead
243 of names. The handle would remain the same even if file names
244 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
245 syscalls.
246
247 config AUDIT
248 bool "Auditing support"
249 depends on NET
250 help
251 Enable auditing infrastructure that can be used with another
252 kernel subsystem, such as SELinux (which requires this for
253 logging of avc messages output). Does not do system-call
254 auditing without CONFIG_AUDITSYSCALL.
255
256 config AUDITSYSCALL
257 bool "Enable system-call auditing support"
258 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT))
259 default y if SECURITY_SELINUX
260 help
261 Enable low-overhead system-call auditing infrastructure that
262 can be used independently or with another kernel subsystem,
263 such as SELinux.
264
265 config AUDIT_WATCH
266 def_bool y
267 depends on AUDITSYSCALL
268 select FSNOTIFY
269
270 config AUDIT_TREE
271 def_bool y
272 depends on AUDITSYSCALL
273 select FSNOTIFY
274
275 config AUDIT_LOGINUID_IMMUTABLE
276 bool "Make audit loginuid immutable"
277 depends on AUDIT
278 help
279 The config option toggles if a task setting its loginuid requires
280 CAP_SYS_AUDITCONTROL or if that task should require no special permissions
281 but should instead only allow setting its loginuid if it was never
282 previously set. On systems which use systemd or a similar central
283 process to restart login services this should be set to true. On older
284 systems in which an admin would typically have to directly stop and
285 start processes this should be set to false. Setting this to true allows
286 one to drop potentially dangerous capabilites from the login tasks,
287 but may not be backwards compatible with older init systems.
288
289 source "kernel/irq/Kconfig"
290 source "kernel/time/Kconfig"
291
292 menu "CPU/Task time and stats accounting"
293
294 config VIRT_CPU_ACCOUNTING
295 bool
296
297 choice
298 prompt "Cputime accounting"
299 default TICK_CPU_ACCOUNTING if !PPC64
300 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
301
302 # Kind of a stub config for the pure tick based cputime accounting
303 config TICK_CPU_ACCOUNTING
304 bool "Simple tick based cputime accounting"
305 depends on !S390
306 help
307 This is the basic tick based cputime accounting that maintains
308 statistics about user, system and idle time spent on per jiffies
309 granularity.
310
311 If unsure, say Y.
312
313 config VIRT_CPU_ACCOUNTING_NATIVE
314 bool "Deterministic task and CPU time accounting"
315 depends on HAVE_VIRT_CPU_ACCOUNTING
316 select VIRT_CPU_ACCOUNTING
317 help
318 Select this option to enable more accurate task and CPU time
319 accounting. This is done by reading a CPU counter on each
320 kernel entry and exit and on transitions within the kernel
321 between system, softirq and hardirq state, so there is a
322 small performance impact. In the case of s390 or IBM POWER > 5,
323 this also enables accounting of stolen time on logically-partitioned
324 systems.
325
326 config VIRT_CPU_ACCOUNTING_GEN
327 bool "Full dynticks CPU time accounting"
328 depends on HAVE_CONTEXT_TRACKING && 64BIT
329 select VIRT_CPU_ACCOUNTING
330 select CONTEXT_TRACKING
331 help
332 Select this option to enable task and CPU time accounting on full
333 dynticks systems. This accounting is implemented by watching every
334 kernel-user boundaries using the context tracking subsystem.
335 The accounting is thus performed at the expense of some significant
336 overhead.
337
338 For now this is only useful if you are working on the full
339 dynticks subsystem development.
340
341 If unsure, say N.
342
343 config IRQ_TIME_ACCOUNTING
344 bool "Fine granularity task level IRQ time accounting"
345 depends on HAVE_IRQ_TIME_ACCOUNTING
346 help
347 Select this option to enable fine granularity task irq time
348 accounting. This is done by reading a timestamp on each
349 transitions between softirq and hardirq state, so there can be a
350 small performance impact.
351
352 If in doubt, say N here.
353
354 endchoice
355
356 config BSD_PROCESS_ACCT
357 bool "BSD Process Accounting"
358 help
359 If you say Y here, a user level program will be able to instruct the
360 kernel (via a special system call) to write process accounting
361 information to a file: whenever a process exits, information about
362 that process will be appended to the file by the kernel. The
363 information includes things such as creation time, owning user,
364 command name, memory usage, controlling terminal etc. (the complete
365 list is in the struct acct in <file:include/linux/acct.h>). It is
366 up to the user level program to do useful things with this
367 information. This is generally a good idea, so say Y.
368
369 config BSD_PROCESS_ACCT_V3
370 bool "BSD Process Accounting version 3 file format"
371 depends on BSD_PROCESS_ACCT
372 default n
373 help
374 If you say Y here, the process accounting information is written
375 in a new file format that also logs the process IDs of each
376 process and it's parent. Note that this file format is incompatible
377 with previous v0/v1/v2 file formats, so you will need updated tools
378 for processing it. A preliminary version of these tools is available
379 at <http://www.gnu.org/software/acct/>.
380
381 config TASKSTATS
382 bool "Export task/process statistics through netlink"
383 depends on NET
384 default n
385 help
386 Export selected statistics for tasks/processes through the
387 generic netlink interface. Unlike BSD process accounting, the
388 statistics are available during the lifetime of tasks/processes as
389 responses to commands. Like BSD accounting, they are sent to user
390 space on task exit.
391
392 Say N if unsure.
393
394 config TASK_DELAY_ACCT
395 bool "Enable per-task delay accounting"
396 depends on TASKSTATS
397 help
398 Collect information on time spent by a task waiting for system
399 resources like cpu, synchronous block I/O completion and swapping
400 in pages. Such statistics can help in setting a task's priorities
401 relative to other tasks for cpu, io, rss limits etc.
402
403 Say N if unsure.
404
405 config TASK_XACCT
406 bool "Enable extended accounting over taskstats"
407 depends on TASKSTATS
408 help
409 Collect extended task accounting data and send the data
410 to userland for processing over the taskstats interface.
411
412 Say N if unsure.
413
414 config TASK_IO_ACCOUNTING
415 bool "Enable per-task storage I/O accounting"
416 depends on TASK_XACCT
417 help
418 Collect information on the number of bytes of storage I/O which this
419 task has caused.
420
421 Say N if unsure.
422
423 endmenu # "CPU/Task time and stats accounting"
424
425 menu "RCU Subsystem"
426
427 choice
428 prompt "RCU Implementation"
429 default TREE_RCU
430
431 config TREE_RCU
432 bool "Tree-based hierarchical RCU"
433 depends on !PREEMPT && SMP
434 help
435 This option selects the RCU implementation that is
436 designed for very large SMP system with hundreds or
437 thousands of CPUs. It also scales down nicely to
438 smaller systems.
439
440 config TREE_PREEMPT_RCU
441 bool "Preemptible tree-based hierarchical RCU"
442 depends on PREEMPT
443 help
444 This option selects the RCU implementation that is
445 designed for very large SMP systems with hundreds or
446 thousands of CPUs, but for which real-time response
447 is also required. It also scales down nicely to
448 smaller systems.
449
450 Select this option if you are unsure.
451
452 config TINY_RCU
453 bool "UP-only small-memory-footprint RCU"
454 depends on !PREEMPT && !SMP
455 help
456 This option selects the RCU implementation that is
457 designed for UP systems from which real-time response
458 is not required. This option greatly reduces the
459 memory footprint of RCU.
460
461 config TINY_PREEMPT_RCU
462 bool "Preemptible UP-only small-memory-footprint RCU"
463 depends on PREEMPT && !SMP
464 help
465 This option selects the RCU implementation that is designed
466 for real-time UP systems. This option greatly reduces the
467 memory footprint of RCU.
468
469 endchoice
470
471 config PREEMPT_RCU
472 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
473 help
474 This option enables preemptible-RCU code that is common between
475 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
476
477 config RCU_STALL_COMMON
478 def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
479 help
480 This option enables RCU CPU stall code that is common between
481 the TINY and TREE variants of RCU. The purpose is to allow
482 the tiny variants to disable RCU CPU stall warnings, while
483 making these warnings mandatory for the tree variants.
484
485 config CONTEXT_TRACKING
486 bool
487
488 config RCU_USER_QS
489 bool "Consider userspace as in RCU extended quiescent state"
490 depends on HAVE_CONTEXT_TRACKING && SMP
491 select CONTEXT_TRACKING
492 help
493 This option sets hooks on kernel / userspace boundaries and
494 puts RCU in extended quiescent state when the CPU runs in
495 userspace. It means that when a CPU runs in userspace, it is
496 excluded from the global RCU state machine and thus doesn't
497 try to keep the timer tick on for RCU.
498
499 Unless you want to hack and help the development of the full
500 dynticks mode, you shouldn't enable this option. It also
501 adds unnecessary overhead.
502
503 If unsure say N
504
505 config CONTEXT_TRACKING_FORCE
506 bool "Force context tracking"
507 depends on CONTEXT_TRACKING
508 help
509 Probe on user/kernel boundaries by default in order to
510 test the features that rely on it such as userspace RCU extended
511 quiescent states.
512 This test is there for debugging until we have a real user like the
513 full dynticks mode.
514
515 config RCU_FANOUT
516 int "Tree-based hierarchical RCU fanout value"
517 range 2 64 if 64BIT
518 range 2 32 if !64BIT
519 depends on TREE_RCU || TREE_PREEMPT_RCU
520 default 64 if 64BIT
521 default 32 if !64BIT
522 help
523 This option controls the fanout of hierarchical implementations
524 of RCU, allowing RCU to work efficiently on machines with
525 large numbers of CPUs. This value must be at least the fourth
526 root of NR_CPUS, which allows NR_CPUS to be insanely large.
527 The default value of RCU_FANOUT should be used for production
528 systems, but if you are stress-testing the RCU implementation
529 itself, small RCU_FANOUT values allow you to test large-system
530 code paths on small(er) systems.
531
532 Select a specific number if testing RCU itself.
533 Take the default if unsure.
534
535 config RCU_FANOUT_LEAF
536 int "Tree-based hierarchical RCU leaf-level fanout value"
537 range 2 RCU_FANOUT if 64BIT
538 range 2 RCU_FANOUT if !64BIT
539 depends on TREE_RCU || TREE_PREEMPT_RCU
540 default 16
541 help
542 This option controls the leaf-level fanout of hierarchical
543 implementations of RCU, and allows trading off cache misses
544 against lock contention. Systems that synchronize their
545 scheduling-clock interrupts for energy-efficiency reasons will
546 want the default because the smaller leaf-level fanout keeps
547 lock contention levels acceptably low. Very large systems
548 (hundreds or thousands of CPUs) will instead want to set this
549 value to the maximum value possible in order to reduce the
550 number of cache misses incurred during RCU's grace-period
551 initialization. These systems tend to run CPU-bound, and thus
552 are not helped by synchronized interrupts, and thus tend to
553 skew them, which reduces lock contention enough that large
554 leaf-level fanouts work well.
555
556 Select a specific number if testing RCU itself.
557
558 Select the maximum permissible value for large systems.
559
560 Take the default if unsure.
561
562 config RCU_FANOUT_EXACT
563 bool "Disable tree-based hierarchical RCU auto-balancing"
564 depends on TREE_RCU || TREE_PREEMPT_RCU
565 default n
566 help
567 This option forces use of the exact RCU_FANOUT value specified,
568 regardless of imbalances in the hierarchy. This is useful for
569 testing RCU itself, and might one day be useful on systems with
570 strong NUMA behavior.
571
572 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
573
574 Say N if unsure.
575
576 config RCU_FAST_NO_HZ
577 bool "Accelerate last non-dyntick-idle CPU's grace periods"
578 depends on NO_HZ && SMP
579 default n
580 help
581 This option permits CPUs to enter dynticks-idle state even if
582 they have RCU callbacks queued, and prevents RCU from waking
583 these CPUs up more than roughly once every four jiffies (by
584 default, you can adjust this using the rcutree.rcu_idle_gp_delay
585 parameter), thus improving energy efficiency. On the other
586 hand, this option increases the duration of RCU grace periods,
587 for example, slowing down synchronize_rcu().
588
589 Say Y if energy efficiency is critically important, and you
590 don't care about increased grace-period durations.
591
592 Say N if you are unsure.
593
594 config TREE_RCU_TRACE
595 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
596 select DEBUG_FS
597 help
598 This option provides tracing for the TREE_RCU and
599 TREE_PREEMPT_RCU implementations, permitting Makefile to
600 trivially select kernel/rcutree_trace.c.
601
602 config RCU_BOOST
603 bool "Enable RCU priority boosting"
604 depends on RT_MUTEXES && PREEMPT_RCU
605 default n
606 help
607 This option boosts the priority of preempted RCU readers that
608 block the current preemptible RCU grace period for too long.
609 This option also prevents heavy loads from blocking RCU
610 callback invocation for all flavors of RCU.
611
612 Say Y here if you are working with real-time apps or heavy loads
613 Say N here if you are unsure.
614
615 config RCU_BOOST_PRIO
616 int "Real-time priority to boost RCU readers to"
617 range 1 99
618 depends on RCU_BOOST
619 default 1
620 help
621 This option specifies the real-time priority to which long-term
622 preempted RCU readers are to be boosted. If you are working
623 with a real-time application that has one or more CPU-bound
624 threads running at a real-time priority level, you should set
625 RCU_BOOST_PRIO to a priority higher then the highest-priority
626 real-time CPU-bound thread. The default RCU_BOOST_PRIO value
627 of 1 is appropriate in the common case, which is real-time
628 applications that do not have any CPU-bound threads.
629
630 Some real-time applications might not have a single real-time
631 thread that saturates a given CPU, but instead might have
632 multiple real-time threads that, taken together, fully utilize
633 that CPU. In this case, you should set RCU_BOOST_PRIO to
634 a priority higher than the lowest-priority thread that is
635 conspiring to prevent the CPU from running any non-real-time
636 tasks. For example, if one thread at priority 10 and another
637 thread at priority 5 are between themselves fully consuming
638 the CPU time on a given CPU, then RCU_BOOST_PRIO should be
639 set to priority 6 or higher.
640
641 Specify the real-time priority, or take the default if unsure.
642
643 config RCU_BOOST_DELAY
644 int "Milliseconds to delay boosting after RCU grace-period start"
645 range 0 3000
646 depends on RCU_BOOST
647 default 500
648 help
649 This option specifies the time to wait after the beginning of
650 a given grace period before priority-boosting preempted RCU
651 readers blocking that grace period. Note that any RCU reader
652 blocking an expedited RCU grace period is boosted immediately.
653
654 Accept the default if unsure.
655
656 config RCU_NOCB_CPU
657 bool "Offload RCU callback processing from boot-selected CPUs (EXPERIMENTAL"
658 depends on TREE_RCU || TREE_PREEMPT_RCU
659 default n
660 help
661 Use this option to reduce OS jitter for aggressive HPC or
662 real-time workloads. It can also be used to offload RCU
663 callback invocation to energy-efficient CPUs in battery-powered
664 asymmetric multiprocessors.
665
666 This option offloads callback invocation from the set of
667 CPUs specified at boot time by the rcu_nocbs parameter.
668 For each such CPU, a kthread ("rcuox/N") will be created to
669 invoke callbacks, where the "N" is the CPU being offloaded,
670 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
671 "s" for RCU-sched. Nothing prevents this kthread from running
672 on the specified CPUs, but (1) the kthreads may be preempted
673 between each callback, and (2) affinity or cgroups can be used
674 to force the kthreads to run on whatever set of CPUs is desired.
675
676 Say Y here if you want to help to debug reduced OS jitter.
677 Say N here if you are unsure.
678
679 choice
680 prompt "Build-forced no-CBs CPUs"
681 default RCU_NOCB_CPU_NONE
682 help
683 This option allows no-CBs CPUs to be specified at build time.
684 Additional no-CBs CPUs may be specified by the rcu_nocbs=
685 boot parameter.
686
687 config RCU_NOCB_CPU_NONE
688 bool "No build_forced no-CBs CPUs"
689 depends on RCU_NOCB_CPU
690 help
691 This option does not force any of the CPUs to be no-CBs CPUs.
692 Only CPUs designated by the rcu_nocbs= boot parameter will be
693 no-CBs CPUs.
694
695 config RCU_NOCB_CPU_ZERO
696 bool "CPU 0 is a build_forced no-CBs CPU"
697 depends on RCU_NOCB_CPU
698 help
699 This option forces CPU 0 to be a no-CBs CPU. Additional CPUs
700 may be designated as no-CBs CPUs using the rcu_nocbs= boot
701 parameter will be no-CBs CPUs.
702
703 Select this if CPU 0 needs to be a no-CBs CPU for real-time
704 or energy-efficiency reasons.
705
706 config RCU_NOCB_CPU_ALL
707 bool "All CPUs are build_forced no-CBs CPUs"
708 depends on RCU_NOCB_CPU
709 help
710 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
711 boot parameter will be ignored.
712
713 Select this if all CPUs need to be no-CBs CPUs for real-time
714 or energy-efficiency reasons.
715
716 endchoice
717
718 endmenu # "RCU Subsystem"
719
720 config IKCONFIG
721 tristate "Kernel .config support"
722 ---help---
723 This option enables the complete Linux kernel ".config" file
724 contents to be saved in the kernel. It provides documentation
725 of which kernel options are used in a running kernel or in an
726 on-disk kernel. This information can be extracted from the kernel
727 image file with the script scripts/extract-ikconfig and used as
728 input to rebuild the current kernel or to build another kernel.
729 It can also be extracted from a running kernel by reading
730 /proc/config.gz if enabled (below).
731
732 config IKCONFIG_PROC
733 bool "Enable access to .config through /proc/config.gz"
734 depends on IKCONFIG && PROC_FS
735 ---help---
736 This option enables access to the kernel configuration file
737 through /proc/config.gz.
738
739 config LOG_BUF_SHIFT
740 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
741 range 12 21
742 default 17
743 help
744 Select kernel log buffer size as a power of 2.
745 Examples:
746 17 => 128 KB
747 16 => 64 KB
748 15 => 32 KB
749 14 => 16 KB
750 13 => 8 KB
751 12 => 4 KB
752
753 #
754 # Architectures with an unreliable sched_clock() should select this:
755 #
756 config HAVE_UNSTABLE_SCHED_CLOCK
757 bool
758
759 #
760 # For architectures that want to enable the support for NUMA-affine scheduler
761 # balancing logic:
762 #
763 config ARCH_SUPPORTS_NUMA_BALANCING
764 bool
765
766 # For architectures that (ab)use NUMA to represent different memory regions
767 # all cpu-local but of different latencies, such as SuperH.
768 #
769 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
770 bool
771
772 #
773 # For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
774 config ARCH_WANTS_PROT_NUMA_PROT_NONE
775 bool
776
777 config ARCH_USES_NUMA_PROT_NONE
778 bool
779 default y
780 depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
781 depends on NUMA_BALANCING
782
783 config NUMA_BALANCING_DEFAULT_ENABLED
784 bool "Automatically enable NUMA aware memory/task placement"
785 default y
786 depends on NUMA_BALANCING
787 help
788 If set, autonumic NUMA balancing will be enabled if running on a NUMA
789 machine.
790
791 config NUMA_BALANCING
792 bool "Memory placement aware NUMA scheduler"
793 depends on ARCH_SUPPORTS_NUMA_BALANCING
794 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
795 depends on SMP && NUMA && MIGRATION
796 help
797 This option adds support for automatic NUMA aware memory/task placement.
798 The mechanism is quite primitive and is based on migrating memory when
799 it is references to the node the task is running on.
800
801 This system will be inactive on UMA systems.
802
803 menuconfig CGROUPS
804 boolean "Control Group support"
805 depends on EVENTFD
806 help
807 This option adds support for grouping sets of processes together, for
808 use with process control subsystems such as Cpusets, CFS, memory
809 controls or device isolation.
810 See
811 - Documentation/scheduler/sched-design-CFS.txt (CFS)
812 - Documentation/cgroups/ (features for grouping, isolation
813 and resource control)
814
815 Say N if unsure.
816
817 if CGROUPS
818
819 config CGROUP_DEBUG
820 bool "Example debug cgroup subsystem"
821 default n
822 help
823 This option enables a simple cgroup subsystem that
824 exports useful debugging information about the cgroups
825 framework.
826
827 Say N if unsure.
828
829 config CGROUP_FREEZER
830 bool "Freezer cgroup subsystem"
831 help
832 Provides a way to freeze and unfreeze all tasks in a
833 cgroup.
834
835 config CGROUP_DEVICE
836 bool "Device controller for cgroups"
837 help
838 Provides a cgroup implementing whitelists for devices which
839 a process in the cgroup can mknod or open.
840
841 config CPUSETS
842 bool "Cpuset support"
843 help
844 This option will let you create and manage CPUSETs which
845 allow dynamically partitioning a system into sets of CPUs and
846 Memory Nodes and assigning tasks to run only within those sets.
847 This is primarily useful on large SMP or NUMA systems.
848
849 Say N if unsure.
850
851 config PROC_PID_CPUSET
852 bool "Include legacy /proc/<pid>/cpuset file"
853 depends on CPUSETS
854 default y
855
856 config CGROUP_CPUACCT
857 bool "Simple CPU accounting cgroup subsystem"
858 help
859 Provides a simple Resource Controller for monitoring the
860 total CPU consumed by the tasks in a cgroup.
861
862 config RESOURCE_COUNTERS
863 bool "Resource counters"
864 help
865 This option enables controller independent resource accounting
866 infrastructure that works with cgroups.
867
868 config MEMCG
869 bool "Memory Resource Controller for Control Groups"
870 depends on RESOURCE_COUNTERS
871 select MM_OWNER
872 help
873 Provides a memory resource controller that manages both anonymous
874 memory and page cache. (See Documentation/cgroups/memory.txt)
875
876 Note that setting this option increases fixed memory overhead
877 associated with each page of memory in the system. By this,
878 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
879 usage tracking struct at boot. Total amount of this is printed out
880 at boot.
881
882 Only enable when you're ok with these trade offs and really
883 sure you need the memory resource controller. Even when you enable
884 this, you can set "cgroup_disable=memory" at your boot option to
885 disable memory resource controller and you can avoid overheads.
886 (and lose benefits of memory resource controller)
887
888 This config option also selects MM_OWNER config option, which
889 could in turn add some fork/exit overhead.
890
891 config MEMCG_SWAP
892 bool "Memory Resource Controller Swap Extension"
893 depends on MEMCG && SWAP
894 help
895 Add swap management feature to memory resource controller. When you
896 enable this, you can limit mem+swap usage per cgroup. In other words,
897 when you disable this, memory resource controller has no cares to
898 usage of swap...a process can exhaust all of the swap. This extension
899 is useful when you want to avoid exhaustion swap but this itself
900 adds more overheads and consumes memory for remembering information.
901 Especially if you use 32bit system or small memory system, please
902 be careful about enabling this. When memory resource controller
903 is disabled by boot option, this will be automatically disabled and
904 there will be no overhead from this. Even when you set this config=y,
905 if boot option "swapaccount=0" is set, swap will not be accounted.
906 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
907 size is 4096bytes, 512k per 1Gbytes of swap.
908 config MEMCG_SWAP_ENABLED
909 bool "Memory Resource Controller Swap Extension enabled by default"
910 depends on MEMCG_SWAP
911 default y
912 help
913 Memory Resource Controller Swap Extension comes with its price in
914 a bigger memory consumption. General purpose distribution kernels
915 which want to enable the feature but keep it disabled by default
916 and let the user enable it by swapaccount boot command line
917 parameter should have this option unselected.
918 For those who want to have the feature enabled by default should
919 select this option (if, for some reason, they need to disable it
920 then swapaccount=0 does the trick).
921 config MEMCG_KMEM
922 bool "Memory Resource Controller Kernel Memory accounting"
923 depends on MEMCG
924 depends on SLUB || SLAB
925 help
926 The Kernel Memory extension for Memory Resource Controller can limit
927 the amount of memory used by kernel objects in the system. Those are
928 fundamentally different from the entities handled by the standard
929 Memory Controller, which are page-based, and can be swapped. Users of
930 the kmem extension can use it to guarantee that no group of processes
931 will ever exhaust kernel resources alone.
932
933 config CGROUP_HUGETLB
934 bool "HugeTLB Resource Controller for Control Groups"
935 depends on RESOURCE_COUNTERS && HUGETLB_PAGE
936 default n
937 help
938 Provides a cgroup Resource Controller for HugeTLB pages.
939 When you enable this, you can put a per cgroup limit on HugeTLB usage.
940 The limit is enforced during page fault. Since HugeTLB doesn't
941 support page reclaim, enforcing the limit at page fault time implies
942 that, the application will get SIGBUS signal if it tries to access
943 HugeTLB pages beyond its limit. This requires the application to know
944 beforehand how much HugeTLB pages it would require for its use. The
945 control group is tracked in the third page lru pointer. This means
946 that we cannot use the controller with huge page less than 3 pages.
947
948 config CGROUP_PERF
949 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
950 depends on PERF_EVENTS && CGROUPS
951 help
952 This option extends the per-cpu mode to restrict monitoring to
953 threads which belong to the cgroup specified and run on the
954 designated cpu.
955
956 Say N if unsure.
957
958 menuconfig CGROUP_SCHED
959 bool "Group CPU scheduler"
960 default n
961 help
962 This feature lets CPU scheduler recognize task groups and control CPU
963 bandwidth allocation to such task groups. It uses cgroups to group
964 tasks.
965
966 if CGROUP_SCHED
967 config FAIR_GROUP_SCHED
968 bool "Group scheduling for SCHED_OTHER"
969 depends on CGROUP_SCHED
970 default CGROUP_SCHED
971
972 config CFS_BANDWIDTH
973 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
974 depends on FAIR_GROUP_SCHED
975 default n
976 help
977 This option allows users to define CPU bandwidth rates (limits) for
978 tasks running within the fair group scheduler. Groups with no limit
979 set are considered to be unconstrained and will run with no
980 restriction.
981 See tip/Documentation/scheduler/sched-bwc.txt for more information.
982
983 config RT_GROUP_SCHED
984 bool "Group scheduling for SCHED_RR/FIFO"
985 depends on CGROUP_SCHED
986 default n
987 help
988 This feature lets you explicitly allocate real CPU bandwidth
989 to task groups. If enabled, it will also make it impossible to
990 schedule realtime tasks for non-root users until you allocate
991 realtime bandwidth for them.
992 See Documentation/scheduler/sched-rt-group.txt for more information.
993
994 endif #CGROUP_SCHED
995
996 config BLK_CGROUP
997 bool "Block IO controller"
998 depends on BLOCK
999 default n
1000 ---help---
1001 Generic block IO controller cgroup interface. This is the common
1002 cgroup interface which should be used by various IO controlling
1003 policies.
1004
1005 Currently, CFQ IO scheduler uses it to recognize task groups and
1006 control disk bandwidth allocation (proportional time slice allocation)
1007 to such task groups. It is also used by bio throttling logic in
1008 block layer to implement upper limit in IO rates on a device.
1009
1010 This option only enables generic Block IO controller infrastructure.
1011 One needs to also enable actual IO controlling logic/policy. For
1012 enabling proportional weight division of disk bandwidth in CFQ, set
1013 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1014 CONFIG_BLK_DEV_THROTTLING=y.
1015
1016 See Documentation/cgroups/blkio-controller.txt for more information.
1017
1018 config DEBUG_BLK_CGROUP
1019 bool "Enable Block IO controller debugging"
1020 depends on BLK_CGROUP
1021 default n
1022 ---help---
1023 Enable some debugging help. Currently it exports additional stat
1024 files in a cgroup which can be useful for debugging.
1025
1026 endif # CGROUPS
1027
1028 config CHECKPOINT_RESTORE
1029 bool "Checkpoint/restore support" if EXPERT
1030 default n
1031 help
1032 Enables additional kernel features in a sake of checkpoint/restore.
1033 In particular it adds auxiliary prctl codes to setup process text,
1034 data and heap segment sizes, and a few additional /proc filesystem
1035 entries.
1036
1037 If unsure, say N here.
1038
1039 menuconfig NAMESPACES
1040 bool "Namespaces support" if EXPERT
1041 default !EXPERT
1042 help
1043 Provides the way to make tasks work with different objects using
1044 the same id. For example same IPC id may refer to different objects
1045 or same user id or pid may refer to different tasks when used in
1046 different namespaces.
1047
1048 if NAMESPACES
1049
1050 config UTS_NS
1051 bool "UTS namespace"
1052 default y
1053 help
1054 In this namespace tasks see different info provided with the
1055 uname() system call
1056
1057 config IPC_NS
1058 bool "IPC namespace"
1059 depends on (SYSVIPC || POSIX_MQUEUE)
1060 default y
1061 help
1062 In this namespace tasks work with IPC ids which correspond to
1063 different IPC objects in different namespaces.
1064
1065 config USER_NS
1066 bool "User namespace"
1067 depends on UIDGID_CONVERTED
1068 select UIDGID_STRICT_TYPE_CHECKS
1069
1070 default n
1071 help
1072 This allows containers, i.e. vservers, to use user namespaces
1073 to provide different user info for different servers.
1074
1075 When user namespaces are enabled in the kernel it is
1076 recommended that the MEMCG and MEMCG_KMEM options also be
1077 enabled and that user-space use the memory control groups to
1078 limit the amount of memory a memory unprivileged users can
1079 use.
1080
1081 If unsure, say N.
1082
1083 config PID_NS
1084 bool "PID Namespaces"
1085 default y
1086 help
1087 Support process id namespaces. This allows having multiple
1088 processes with the same pid as long as they are in different
1089 pid namespaces. This is a building block of containers.
1090
1091 config NET_NS
1092 bool "Network namespace"
1093 depends on NET
1094 default y
1095 help
1096 Allow user space to create what appear to be multiple instances
1097 of the network stack.
1098
1099 endif # NAMESPACES
1100
1101 config UIDGID_CONVERTED
1102 # True if all of the selected software conmponents are known
1103 # to have uid_t and gid_t converted to kuid_t and kgid_t
1104 # where appropriate and are otherwise safe to use with
1105 # the user namespace.
1106 bool
1107 default y
1108
1109 # Filesystems
1110 depends on XFS_FS = n
1111
1112 config UIDGID_STRICT_TYPE_CHECKS
1113 bool "Require conversions between uid/gids and their internal representation"
1114 depends on UIDGID_CONVERTED
1115 default n
1116 help
1117 While the nececessary conversions are being added to all subsystems this option allows
1118 the code to continue to build for unconverted subsystems.
1119
1120 Say Y here if you want the strict type checking enabled
1121
1122 config SCHED_AUTOGROUP
1123 bool "Automatic process group scheduling"
1124 select EVENTFD
1125 select CGROUPS
1126 select CGROUP_SCHED
1127 select FAIR_GROUP_SCHED
1128 help
1129 This option optimizes the scheduler for common desktop workloads by
1130 automatically creating and populating task groups. This separation
1131 of workloads isolates aggressive CPU burners (like build jobs) from
1132 desktop applications. Task group autogeneration is currently based
1133 upon task session.
1134
1135 config MM_OWNER
1136 bool
1137
1138 config SYSFS_DEPRECATED
1139 bool "Enable deprecated sysfs features to support old userspace tools"
1140 depends on SYSFS
1141 default n
1142 help
1143 This option adds code that switches the layout of the "block" class
1144 devices, to not show up in /sys/class/block/, but only in
1145 /sys/block/.
1146
1147 This switch is only active when the sysfs.deprecated=1 boot option is
1148 passed or the SYSFS_DEPRECATED_V2 option is set.
1149
1150 This option allows new kernels to run on old distributions and tools,
1151 which might get confused by /sys/class/block/. Since 2007/2008 all
1152 major distributions and tools handle this just fine.
1153
1154 Recent distributions and userspace tools after 2009/2010 depend on
1155 the existence of /sys/class/block/, and will not work with this
1156 option enabled.
1157
1158 Only if you are using a new kernel on an old distribution, you might
1159 need to say Y here.
1160
1161 config SYSFS_DEPRECATED_V2
1162 bool "Enable deprecated sysfs features by default"
1163 default n
1164 depends on SYSFS
1165 depends on SYSFS_DEPRECATED
1166 help
1167 Enable deprecated sysfs by default.
1168
1169 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1170 option.
1171
1172 Only if you are using a new kernel on an old distribution, you might
1173 need to say Y here. Even then, odds are you would not need it
1174 enabled, you can always pass the boot option if absolutely necessary.
1175
1176 config RELAY
1177 bool "Kernel->user space relay support (formerly relayfs)"
1178 help
1179 This option enables support for relay interface support in
1180 certain file systems (such as debugfs).
1181 It is designed to provide an efficient mechanism for tools and
1182 facilities to relay large amounts of data from kernel space to
1183 user space.
1184
1185 If unsure, say N.
1186
1187 config BLK_DEV_INITRD
1188 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1189 depends on BROKEN || !FRV
1190 help
1191 The initial RAM filesystem is a ramfs which is loaded by the
1192 boot loader (loadlin or lilo) and that is mounted as root
1193 before the normal boot procedure. It is typically used to
1194 load modules needed to mount the "real" root file system,
1195 etc. See <file:Documentation/initrd.txt> for details.
1196
1197 If RAM disk support (BLK_DEV_RAM) is also included, this
1198 also enables initial RAM disk (initrd) support and adds
1199 15 Kbytes (more on some other architectures) to the kernel size.
1200
1201 If unsure say Y.
1202
1203 if BLK_DEV_INITRD
1204
1205 source "usr/Kconfig"
1206
1207 endif
1208
1209 config CC_OPTIMIZE_FOR_SIZE
1210 bool "Optimize for size"
1211 help
1212 Enabling this option will pass "-Os" instead of "-O2" to gcc
1213 resulting in a smaller kernel.
1214
1215 If unsure, say N.
1216
1217 config SYSCTL
1218 bool
1219
1220 config ANON_INODES
1221 bool
1222
1223 menuconfig EXPERT
1224 bool "Configure standard kernel features (expert users)"
1225 # Unhide debug options, to make the on-by-default options visible
1226 select DEBUG_KERNEL
1227 help
1228 This option allows certain base kernel options and settings
1229 to be disabled or tweaked. This is for specialized
1230 environments which can tolerate a "non-standard" kernel.
1231 Only use this if you really know what you are doing.
1232
1233 config HAVE_UID16
1234 bool
1235
1236 config UID16
1237 bool "Enable 16-bit UID system calls" if EXPERT
1238 depends on HAVE_UID16
1239 default y
1240 help
1241 This enables the legacy 16-bit UID syscall wrappers.
1242
1243 config SYSCTL_SYSCALL
1244 bool "Sysctl syscall support" if EXPERT
1245 depends on PROC_SYSCTL
1246 default n
1247 select SYSCTL
1248 ---help---
1249 sys_sysctl uses binary paths that have been found challenging
1250 to properly maintain and use. The interface in /proc/sys
1251 using paths with ascii names is now the primary path to this
1252 information.
1253
1254 Almost nothing using the binary sysctl interface so if you are
1255 trying to save some space it is probably safe to disable this,
1256 making your kernel marginally smaller.
1257
1258 If unsure say N here.
1259
1260 config SYSCTL_EXCEPTION_TRACE
1261 bool
1262 help
1263 Enable support for /proc/sys/debug/exception-trace.
1264
1265 config SYSCTL_ARCH_UNALIGN_NO_WARN
1266 bool
1267 help
1268 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1269 Allows arch to define/use @no_unaligned_warning to possibly warn
1270 about unaligned access emulation going on under the hood.
1271
1272 config SYSCTL_ARCH_UNALIGN_ALLOW
1273 bool
1274 help
1275 Enable support for /proc/sys/kernel/unaligned-trap
1276 Allows arches to define/use @unaligned_enabled to runtime toggle
1277 the unaligned access emulation.
1278 see arch/parisc/kernel/unaligned.c for reference
1279
1280 config KALLSYMS
1281 bool "Load all symbols for debugging/ksymoops" if EXPERT
1282 default y
1283 help
1284 Say Y here to let the kernel print out symbolic crash information and
1285 symbolic stack backtraces. This increases the size of the kernel
1286 somewhat, as all symbols have to be loaded into the kernel image.
1287
1288 config KALLSYMS_ALL
1289 bool "Include all symbols in kallsyms"
1290 depends on DEBUG_KERNEL && KALLSYMS
1291 help
1292 Normally kallsyms only contains the symbols of functions for nicer
1293 OOPS messages and backtraces (i.e., symbols from the text and inittext
1294 sections). This is sufficient for most cases. And only in very rare
1295 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1296 names of variables from the data sections, etc).
1297
1298 This option makes sure that all symbols are loaded into the kernel
1299 image (i.e., symbols from all sections) in cost of increased kernel
1300 size (depending on the kernel configuration, it may be 300KiB or
1301 something like this).
1302
1303 Say N unless you really need all symbols.
1304
1305 config HOTPLUG
1306 def_bool y
1307
1308 config PRINTK
1309 default y
1310 bool "Enable support for printk" if EXPERT
1311 select IRQ_WORK
1312 help
1313 This option enables normal printk support. Removing it
1314 eliminates most of the message strings from the kernel image
1315 and makes the kernel more or less silent. As this makes it
1316 very difficult to diagnose system problems, saying N here is
1317 strongly discouraged.
1318
1319 config BUG
1320 bool "BUG() support" if EXPERT
1321 default y
1322 help
1323 Disabling this option eliminates support for BUG and WARN, reducing
1324 the size of your kernel image and potentially quietly ignoring
1325 numerous fatal conditions. You should only consider disabling this
1326 option for embedded systems with no facilities for reporting errors.
1327 Just say Y.
1328
1329 config ELF_CORE
1330 depends on COREDUMP
1331 default y
1332 bool "Enable ELF core dumps" if EXPERT
1333 help
1334 Enable support for generating core dumps. Disabling saves about 4k.
1335
1336
1337 config PCSPKR_PLATFORM
1338 bool "Enable PC-Speaker support" if EXPERT
1339 depends on HAVE_PCSPKR_PLATFORM
1340 select I8253_LOCK
1341 default y
1342 help
1343 This option allows to disable the internal PC-Speaker
1344 support, saving some memory.
1345
1346 config HAVE_PCSPKR_PLATFORM
1347 bool
1348
1349 config BASE_FULL
1350 default y
1351 bool "Enable full-sized data structures for core" if EXPERT
1352 help
1353 Disabling this option reduces the size of miscellaneous core
1354 kernel data structures. This saves memory on small machines,
1355 but may reduce performance.
1356
1357 config FUTEX
1358 bool "Enable futex support" if EXPERT
1359 default y
1360 select RT_MUTEXES
1361 help
1362 Disabling this option will cause the kernel to be built without
1363 support for "fast userspace mutexes". The resulting kernel may not
1364 run glibc-based applications correctly.
1365
1366 config EPOLL
1367 bool "Enable eventpoll support" if EXPERT
1368 default y
1369 select ANON_INODES
1370 help
1371 Disabling this option will cause the kernel to be built without
1372 support for epoll family of system calls.
1373
1374 config SIGNALFD
1375 bool "Enable signalfd() system call" if EXPERT
1376 select ANON_INODES
1377 default y
1378 help
1379 Enable the signalfd() system call that allows to receive signals
1380 on a file descriptor.
1381
1382 If unsure, say Y.
1383
1384 config TIMERFD
1385 bool "Enable timerfd() system call" if EXPERT
1386 select ANON_INODES
1387 default y
1388 help
1389 Enable the timerfd() system call that allows to receive timer
1390 events on a file descriptor.
1391
1392 If unsure, say Y.
1393
1394 config EVENTFD
1395 bool "Enable eventfd() system call" if EXPERT
1396 select ANON_INODES
1397 default y
1398 help
1399 Enable the eventfd() system call that allows to receive both
1400 kernel notification (ie. KAIO) or userspace notifications.
1401
1402 If unsure, say Y.
1403
1404 config SHMEM
1405 bool "Use full shmem filesystem" if EXPERT
1406 default y
1407 depends on MMU
1408 help
1409 The shmem is an internal filesystem used to manage shared memory.
1410 It is backed by swap and manages resource limits. It is also exported
1411 to userspace as tmpfs if TMPFS is enabled. Disabling this
1412 option replaces shmem and tmpfs with the much simpler ramfs code,
1413 which may be appropriate on small systems without swap.
1414
1415 config AIO
1416 bool "Enable AIO support" if EXPERT
1417 default y
1418 help
1419 This option enables POSIX asynchronous I/O which may by used
1420 by some high performance threaded applications. Disabling
1421 this option saves about 7k.
1422
1423 config EMBEDDED
1424 bool "Embedded system"
1425 select EXPERT
1426 help
1427 This option should be enabled if compiling the kernel for
1428 an embedded system so certain expert options are available
1429 for configuration.
1430
1431 config HAVE_PERF_EVENTS
1432 bool
1433 help
1434 See tools/perf/design.txt for details.
1435
1436 config PERF_USE_VMALLOC
1437 bool
1438 help
1439 See tools/perf/design.txt for details
1440
1441 menu "Kernel Performance Events And Counters"
1442
1443 config PERF_EVENTS
1444 bool "Kernel performance events and counters"
1445 default y if PROFILING
1446 depends on HAVE_PERF_EVENTS
1447 select ANON_INODES
1448 select IRQ_WORK
1449 help
1450 Enable kernel support for various performance events provided
1451 by software and hardware.
1452
1453 Software events are supported either built-in or via the
1454 use of generic tracepoints.
1455
1456 Most modern CPUs support performance events via performance
1457 counter registers. These registers count the number of certain
1458 types of hw events: such as instructions executed, cachemisses
1459 suffered, or branches mis-predicted - without slowing down the
1460 kernel or applications. These registers can also trigger interrupts
1461 when a threshold number of events have passed - and can thus be
1462 used to profile the code that runs on that CPU.
1463
1464 The Linux Performance Event subsystem provides an abstraction of
1465 these software and hardware event capabilities, available via a
1466 system call and used by the "perf" utility in tools/perf/. It
1467 provides per task and per CPU counters, and it provides event
1468 capabilities on top of those.
1469
1470 Say Y if unsure.
1471
1472 config DEBUG_PERF_USE_VMALLOC
1473 default n
1474 bool "Debug: use vmalloc to back perf mmap() buffers"
1475 depends on PERF_EVENTS && DEBUG_KERNEL
1476 select PERF_USE_VMALLOC
1477 help
1478 Use vmalloc memory to back perf mmap() buffers.
1479
1480 Mostly useful for debugging the vmalloc code on platforms
1481 that don't require it.
1482
1483 Say N if unsure.
1484
1485 endmenu
1486
1487 config VM_EVENT_COUNTERS
1488 default y
1489 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1490 help
1491 VM event counters are needed for event counts to be shown.
1492 This option allows the disabling of the VM event counters
1493 on EXPERT systems. /proc/vmstat will only show page counts
1494 if VM event counters are disabled.
1495
1496 config PCI_QUIRKS
1497 default y
1498 bool "Enable PCI quirk workarounds" if EXPERT
1499 depends on PCI
1500 help
1501 This enables workarounds for various PCI chipset
1502 bugs/quirks. Disable this only if your target machine is
1503 unaffected by PCI quirks.
1504
1505 config SLUB_DEBUG
1506 default y
1507 bool "Enable SLUB debugging support" if EXPERT
1508 depends on SLUB && SYSFS
1509 help
1510 SLUB has extensive debug support features. Disabling these can
1511 result in significant savings in code size. This also disables
1512 SLUB sysfs support. /sys/slab will not exist and there will be
1513 no support for cache validation etc.
1514
1515 config COMPAT_BRK
1516 bool "Disable heap randomization"
1517 default y
1518 help
1519 Randomizing heap placement makes heap exploits harder, but it
1520 also breaks ancient binaries (including anything libc5 based).
1521 This option changes the bootup default to heap randomization
1522 disabled, and can be overridden at runtime by setting
1523 /proc/sys/kernel/randomize_va_space to 2.
1524
1525 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1526
1527 choice
1528 prompt "Choose SLAB allocator"
1529 default SLUB
1530 help
1531 This option allows to select a slab allocator.
1532
1533 config SLAB
1534 bool "SLAB"
1535 help
1536 The regular slab allocator that is established and known to work
1537 well in all environments. It organizes cache hot objects in
1538 per cpu and per node queues.
1539
1540 config SLUB
1541 bool "SLUB (Unqueued Allocator)"
1542 help
1543 SLUB is a slab allocator that minimizes cache line usage
1544 instead of managing queues of cached objects (SLAB approach).
1545 Per cpu caching is realized using slabs of objects instead
1546 of queues of objects. SLUB can use memory efficiently
1547 and has enhanced diagnostics. SLUB is the default choice for
1548 a slab allocator.
1549
1550 config SLOB
1551 depends on EXPERT
1552 bool "SLOB (Simple Allocator)"
1553 help
1554 SLOB replaces the stock allocator with a drastically simpler
1555 allocator. SLOB is generally more space efficient but
1556 does not perform as well on large systems.
1557
1558 endchoice
1559
1560 config MMAP_ALLOW_UNINITIALIZED
1561 bool "Allow mmapped anonymous memory to be uninitialized"
1562 depends on EXPERT && !MMU
1563 default n
1564 help
1565 Normally, and according to the Linux spec, anonymous memory obtained
1566 from mmap() has it's contents cleared before it is passed to
1567 userspace. Enabling this config option allows you to request that
1568 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1569 providing a huge performance boost. If this option is not enabled,
1570 then the flag will be ignored.
1571
1572 This is taken advantage of by uClibc's malloc(), and also by
1573 ELF-FDPIC binfmt's brk and stack allocator.
1574
1575 Because of the obvious security issues, this option should only be
1576 enabled on embedded devices where you control what is run in
1577 userspace. Since that isn't generally a problem on no-MMU systems,
1578 it is normally safe to say Y here.
1579
1580 See Documentation/nommu-mmap.txt for more information.
1581
1582 config PROFILING
1583 bool "Profiling support"
1584 help
1585 Say Y here to enable the extended profiling support mechanisms used
1586 by profilers such as OProfile.
1587
1588 #
1589 # Place an empty function call at each tracepoint site. Can be
1590 # dynamically changed for a probe function.
1591 #
1592 config TRACEPOINTS
1593 bool
1594
1595 source "arch/Kconfig"
1596
1597 endmenu # General setup
1598
1599 config HAVE_GENERIC_DMA_COHERENT
1600 bool
1601 default n
1602
1603 config SLABINFO
1604 bool
1605 depends on PROC_FS
1606 depends on SLAB || SLUB_DEBUG
1607 default y
1608
1609 config RT_MUTEXES
1610 boolean
1611
1612 config BASE_SMALL
1613 int
1614 default 0 if BASE_FULL
1615 default 1 if !BASE_FULL
1616
1617 menuconfig MODULES
1618 bool "Enable loadable module support"
1619 help
1620 Kernel modules are small pieces of compiled code which can
1621 be inserted in the running kernel, rather than being
1622 permanently built into the kernel. You use the "modprobe"
1623 tool to add (and sometimes remove) them. If you say Y here,
1624 many parts of the kernel can be built as modules (by
1625 answering M instead of Y where indicated): this is most
1626 useful for infrequently used options which are not required
1627 for booting. For more information, see the man pages for
1628 modprobe, lsmod, modinfo, insmod and rmmod.
1629
1630 If you say Y here, you will need to run "make
1631 modules_install" to put the modules under /lib/modules/
1632 where modprobe can find them (you may need to be root to do
1633 this).
1634
1635 If unsure, say Y.
1636
1637 if MODULES
1638
1639 config MODULE_FORCE_LOAD
1640 bool "Forced module loading"
1641 default n
1642 help
1643 Allow loading of modules without version information (ie. modprobe
1644 --force). Forced module loading sets the 'F' (forced) taint flag and
1645 is usually a really bad idea.
1646
1647 config MODULE_UNLOAD
1648 bool "Module unloading"
1649 help
1650 Without this option you will not be able to unload any
1651 modules (note that some modules may not be unloadable
1652 anyway), which makes your kernel smaller, faster
1653 and simpler. If unsure, say Y.
1654
1655 config MODULE_FORCE_UNLOAD
1656 bool "Forced module unloading"
1657 depends on MODULE_UNLOAD
1658 help
1659 This option allows you to force a module to unload, even if the
1660 kernel believes it is unsafe: the kernel will remove the module
1661 without waiting for anyone to stop using it (using the -f option to
1662 rmmod). This is mainly for kernel developers and desperate users.
1663 If unsure, say N.
1664
1665 config MODVERSIONS
1666 bool "Module versioning support"
1667 help
1668 Usually, you have to use modules compiled with your kernel.
1669 Saying Y here makes it sometimes possible to use modules
1670 compiled for different kernels, by adding enough information
1671 to the modules to (hopefully) spot any changes which would
1672 make them incompatible with the kernel you are running. If
1673 unsure, say N.
1674
1675 config MODULE_SRCVERSION_ALL
1676 bool "Source checksum for all modules"
1677 help
1678 Modules which contain a MODULE_VERSION get an extra "srcversion"
1679 field inserted into their modinfo section, which contains a
1680 sum of the source files which made it. This helps maintainers
1681 see exactly which source was used to build a module (since
1682 others sometimes change the module source without updating
1683 the version). With this option, such a "srcversion" field
1684 will be created for all modules. If unsure, say N.
1685
1686 config MODULE_SIG
1687 bool "Module signature verification"
1688 depends on MODULES
1689 select KEYS
1690 select CRYPTO
1691 select ASYMMETRIC_KEY_TYPE
1692 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1693 select PUBLIC_KEY_ALGO_RSA
1694 select ASN1
1695 select OID_REGISTRY
1696 select X509_CERTIFICATE_PARSER
1697 help
1698 Check modules for valid signatures upon load: the signature
1699 is simply appended to the module. For more information see
1700 Documentation/module-signing.txt.
1701
1702 !!!WARNING!!! If you enable this option, you MUST make sure that the
1703 module DOES NOT get stripped after being signed. This includes the
1704 debuginfo strip done by some packagers (such as rpmbuild) and
1705 inclusion into an initramfs that wants the module size reduced.
1706
1707 config MODULE_SIG_FORCE
1708 bool "Require modules to be validly signed"
1709 depends on MODULE_SIG
1710 help
1711 Reject unsigned modules or signed modules for which we don't have a
1712 key. Without this, such modules will simply taint the kernel.
1713
1714 config MODULE_SIG_ALL
1715 bool "Automatically sign all modules"
1716 default y
1717 depends on MODULE_SIG
1718 help
1719 Sign all modules during make modules_install. Without this option,
1720 modules must be signed manually, using the scripts/sign-file tool.
1721
1722 comment "Do not forget to sign required modules with scripts/sign-file"
1723 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1724
1725 choice
1726 prompt "Which hash algorithm should modules be signed with?"
1727 depends on MODULE_SIG
1728 help
1729 This determines which sort of hashing algorithm will be used during
1730 signature generation. This algorithm _must_ be built into the kernel
1731 directly so that signature verification can take place. It is not
1732 possible to load a signed module containing the algorithm to check
1733 the signature on that module.
1734
1735 config MODULE_SIG_SHA1
1736 bool "Sign modules with SHA-1"
1737 select CRYPTO_SHA1
1738
1739 config MODULE_SIG_SHA224
1740 bool "Sign modules with SHA-224"
1741 select CRYPTO_SHA256
1742
1743 config MODULE_SIG_SHA256
1744 bool "Sign modules with SHA-256"
1745 select CRYPTO_SHA256
1746
1747 config MODULE_SIG_SHA384
1748 bool "Sign modules with SHA-384"
1749 select CRYPTO_SHA512
1750
1751 config MODULE_SIG_SHA512
1752 bool "Sign modules with SHA-512"
1753 select CRYPTO_SHA512
1754
1755 endchoice
1756
1757 config MODULE_SIG_HASH
1758 string
1759 depends on MODULE_SIG
1760 default "sha1" if MODULE_SIG_SHA1
1761 default "sha224" if MODULE_SIG_SHA224
1762 default "sha256" if MODULE_SIG_SHA256
1763 default "sha384" if MODULE_SIG_SHA384
1764 default "sha512" if MODULE_SIG_SHA512
1765
1766 endif # MODULES
1767
1768 config INIT_ALL_POSSIBLE
1769 bool
1770 help
1771 Back when each arch used to define their own cpu_online_mask and
1772 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1773 with all 1s, and others with all 0s. When they were centralised,
1774 it was better to provide this option than to break all the archs
1775 and have several arch maintainers pursuing me down dark alleys.
1776
1777 config STOP_MACHINE
1778 bool
1779 default y
1780 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1781 help
1782 Need stop_machine() primitive.
1783
1784 source "block/Kconfig"
1785
1786 config PREEMPT_NOTIFIERS
1787 bool
1788
1789 config PADATA
1790 depends on SMP
1791 bool
1792
1793 # Can be selected by architectures with broken toolchains
1794 # that get confused by correct const<->read_only section
1795 # mappings
1796 config BROKEN_RODATA
1797 bool
1798
1799 config ASN1
1800 tristate
1801 help
1802 Build a simple ASN.1 grammar compiler that produces a bytecode output
1803 that can be interpreted by the ASN.1 stream decoder and used to
1804 inform it as to what tags are to be expected in a stream and what
1805 functions to call on what tags.
1806
1807 source "kernel/Kconfig.locks"