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git.proxmox.com Git - mirror_ubuntu-jammy-kernel.git/blob - lib/percpu_ida.c
4 * Copyright (C) 2013 Datera, Inc. Kent Overstreet
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License as
8 * published by the Free Software Foundation; either version 2, or (at
9 * your option) any later version.
11 * This program is distributed in the hope that it will be useful, but
12 * WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * General Public License for more details.
17 #include <linux/bitmap.h>
18 #include <linux/bitops.h>
19 #include <linux/bug.h>
20 #include <linux/err.h>
21 #include <linux/export.h>
22 #include <linux/hardirq.h>
23 #include <linux/idr.h>
24 #include <linux/init.h>
25 #include <linux/kernel.h>
26 #include <linux/percpu.h>
27 #include <linux/sched.h>
28 #include <linux/slab.h>
29 #include <linux/string.h>
30 #include <linux/spinlock.h>
31 #include <linux/percpu_ida.h>
33 struct percpu_ida_cpu
{
35 * Even though this is percpu, we need a lock for tag stealing by remote
40 /* nr_free/freelist form a stack of free IDs */
45 static inline void move_tags(unsigned *dst
, unsigned *dst_nr
,
46 unsigned *src
, unsigned *src_nr
,
50 memcpy(dst
+ *dst_nr
, src
+ *src_nr
, sizeof(unsigned) * nr
);
55 * Try to steal tags from a remote cpu's percpu freelist.
57 * We first check how many percpu freelists have tags
59 * Then we iterate through the cpus until we find some tags - we don't attempt
60 * to find the "best" cpu to steal from, to keep cacheline bouncing to a
63 static inline void steal_tags(struct percpu_ida
*pool
,
64 struct percpu_ida_cpu
*tags
)
66 unsigned cpus_have_tags
, cpu
= pool
->cpu_last_stolen
;
67 struct percpu_ida_cpu
*remote
;
69 for (cpus_have_tags
= cpumask_weight(&pool
->cpus_have_tags
);
70 cpus_have_tags
; cpus_have_tags
--) {
71 cpu
= cpumask_next(cpu
, &pool
->cpus_have_tags
);
73 if (cpu
>= nr_cpu_ids
) {
74 cpu
= cpumask_first(&pool
->cpus_have_tags
);
75 if (cpu
>= nr_cpu_ids
)
79 pool
->cpu_last_stolen
= cpu
;
80 remote
= per_cpu_ptr(pool
->tag_cpu
, cpu
);
82 cpumask_clear_cpu(cpu
, &pool
->cpus_have_tags
);
87 spin_lock(&remote
->lock
);
89 if (remote
->nr_free
) {
90 memcpy(tags
->freelist
,
92 sizeof(unsigned) * remote
->nr_free
);
94 tags
->nr_free
= remote
->nr_free
;
98 spin_unlock(&remote
->lock
);
106 * Pop up to IDA_PCPU_BATCH_MOVE IDs off the global freelist, and push them onto
107 * our percpu freelist:
109 static inline void alloc_global_tags(struct percpu_ida
*pool
,
110 struct percpu_ida_cpu
*tags
)
112 move_tags(tags
->freelist
, &tags
->nr_free
,
113 pool
->freelist
, &pool
->nr_free
,
114 min(pool
->nr_free
, pool
->percpu_batch_size
));
117 static inline unsigned alloc_local_tag(struct percpu_ida_cpu
*tags
)
121 spin_lock(&tags
->lock
);
123 tag
= tags
->freelist
[--tags
->nr_free
];
124 spin_unlock(&tags
->lock
);
130 * percpu_ida_alloc - allocate a tag
131 * @pool: pool to allocate from
132 * @state: task state for prepare_to_wait
134 * Returns a tag - an integer in the range [0..nr_tags) (passed to
135 * tag_pool_init()), or otherwise -ENOSPC on allocation failure.
137 * Safe to be called from interrupt context (assuming it isn't passed
138 * TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE, of course).
140 * @gfp indicates whether or not to wait until a free id is available (it's not
141 * used for internal memory allocations); thus if passed __GFP_WAIT we may sleep
142 * however long it takes until another thread frees an id (same semantics as a
145 * Will not fail if passed TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE.
147 int percpu_ida_alloc(struct percpu_ida
*pool
, int state
)
150 struct percpu_ida_cpu
*tags
;
154 local_irq_save(flags
);
155 tags
= this_cpu_ptr(pool
->tag_cpu
);
158 tag
= alloc_local_tag(tags
);
159 if (likely(tag
>= 0)) {
160 local_irq_restore(flags
);
165 spin_lock(&pool
->lock
);
168 * prepare_to_wait() must come before steal_tags(), in case
169 * percpu_ida_free() on another cpu flips a bit in
172 * global lock held and irqs disabled, don't need percpu lock
174 if (state
!= TASK_RUNNING
)
175 prepare_to_wait(&pool
->wait
, &wait
, state
);
178 alloc_global_tags(pool
, tags
);
180 steal_tags(pool
, tags
);
183 tag
= tags
->freelist
[--tags
->nr_free
];
185 cpumask_set_cpu(smp_processor_id(),
186 &pool
->cpus_have_tags
);
189 spin_unlock(&pool
->lock
);
190 local_irq_restore(flags
);
192 if (tag
>= 0 || state
== TASK_RUNNING
)
195 if (signal_pending_state(state
, current
)) {
202 local_irq_save(flags
);
203 tags
= this_cpu_ptr(pool
->tag_cpu
);
205 if (state
!= TASK_RUNNING
)
206 finish_wait(&pool
->wait
, &wait
);
210 EXPORT_SYMBOL_GPL(percpu_ida_alloc
);
213 * percpu_ida_free - free a tag
214 * @pool: pool @tag was allocated from
215 * @tag: a tag previously allocated with percpu_ida_alloc()
217 * Safe to be called from interrupt context.
219 void percpu_ida_free(struct percpu_ida
*pool
, unsigned tag
)
221 struct percpu_ida_cpu
*tags
;
225 BUG_ON(tag
>= pool
->nr_tags
);
227 local_irq_save(flags
);
228 tags
= this_cpu_ptr(pool
->tag_cpu
);
230 spin_lock(&tags
->lock
);
231 tags
->freelist
[tags
->nr_free
++] = tag
;
233 nr_free
= tags
->nr_free
;
234 spin_unlock(&tags
->lock
);
237 cpumask_set_cpu(smp_processor_id(),
238 &pool
->cpus_have_tags
);
239 wake_up(&pool
->wait
);
242 if (nr_free
== pool
->percpu_max_size
) {
243 spin_lock(&pool
->lock
);
246 * Global lock held and irqs disabled, don't need percpu
249 if (tags
->nr_free
== pool
->percpu_max_size
) {
250 move_tags(pool
->freelist
, &pool
->nr_free
,
251 tags
->freelist
, &tags
->nr_free
,
252 pool
->percpu_batch_size
);
254 wake_up(&pool
->wait
);
256 spin_unlock(&pool
->lock
);
259 local_irq_restore(flags
);
261 EXPORT_SYMBOL_GPL(percpu_ida_free
);
264 * percpu_ida_destroy - release a tag pool's resources
265 * @pool: pool to free
267 * Frees the resources allocated by percpu_ida_init().
269 void percpu_ida_destroy(struct percpu_ida
*pool
)
271 free_percpu(pool
->tag_cpu
);
272 free_pages((unsigned long) pool
->freelist
,
273 get_order(pool
->nr_tags
* sizeof(unsigned)));
275 EXPORT_SYMBOL_GPL(percpu_ida_destroy
);
278 * percpu_ida_init - initialize a percpu tag pool
279 * @pool: pool to initialize
280 * @nr_tags: number of tags that will be available for allocation
282 * Initializes @pool so that it can be used to allocate tags - integers in the
283 * range [0, nr_tags). Typically, they'll be used by driver code to refer to a
284 * preallocated array of tag structures.
286 * Allocation is percpu, but sharding is limited by nr_tags - for best
287 * performance, the workload should not span more cpus than nr_tags / 128.
289 int __percpu_ida_init(struct percpu_ida
*pool
, unsigned long nr_tags
,
290 unsigned long max_size
, unsigned long batch_size
)
292 unsigned i
, cpu
, order
;
294 memset(pool
, 0, sizeof(*pool
));
296 init_waitqueue_head(&pool
->wait
);
297 spin_lock_init(&pool
->lock
);
298 pool
->nr_tags
= nr_tags
;
299 pool
->percpu_max_size
= max_size
;
300 pool
->percpu_batch_size
= batch_size
;
302 /* Guard against overflow */
303 if (nr_tags
> (unsigned) INT_MAX
+ 1) {
304 pr_err("percpu_ida_init(): nr_tags too large\n");
308 order
= get_order(nr_tags
* sizeof(unsigned));
309 pool
->freelist
= (void *) __get_free_pages(GFP_KERNEL
, order
);
313 for (i
= 0; i
< nr_tags
; i
++)
314 pool
->freelist
[i
] = i
;
316 pool
->nr_free
= nr_tags
;
318 pool
->tag_cpu
= __alloc_percpu(sizeof(struct percpu_ida_cpu
) +
319 pool
->percpu_max_size
* sizeof(unsigned),
324 for_each_possible_cpu(cpu
)
325 spin_lock_init(&per_cpu_ptr(pool
->tag_cpu
, cpu
)->lock
);
329 percpu_ida_destroy(pool
);
332 EXPORT_SYMBOL_GPL(__percpu_ida_init
);
335 * percpu_ida_for_each_free - iterate free ids of a pool
336 * @pool: pool to iterate
337 * @fn: interate callback function
338 * @data: parameter for @fn
340 * Note, this doesn't guarantee to iterate all free ids restrictly. Some free
341 * ids might be missed, some might be iterated duplicated, and some might
342 * be iterated and not free soon.
344 int percpu_ida_for_each_free(struct percpu_ida
*pool
, percpu_ida_cb fn
,
348 struct percpu_ida_cpu
*remote
;
349 unsigned cpu
, i
, err
= 0;
351 local_irq_save(flags
);
352 for_each_possible_cpu(cpu
) {
353 remote
= per_cpu_ptr(pool
->tag_cpu
, cpu
);
354 spin_lock(&remote
->lock
);
355 for (i
= 0; i
< remote
->nr_free
; i
++) {
356 err
= fn(remote
->freelist
[i
], data
);
360 spin_unlock(&remote
->lock
);
365 spin_lock(&pool
->lock
);
366 for (i
= 0; i
< pool
->nr_free
; i
++) {
367 err
= fn(pool
->freelist
[i
], data
);
371 spin_unlock(&pool
->lock
);
373 local_irq_restore(flags
);
376 EXPORT_SYMBOL_GPL(percpu_ida_for_each_free
);
379 * percpu_ida_free_tags - return free tags number of a specific cpu or global pool
380 * @pool: pool related
381 * @cpu: specific cpu or global pool if @cpu == nr_cpu_ids
383 * Note: this just returns a snapshot of free tags number.
385 unsigned percpu_ida_free_tags(struct percpu_ida
*pool
, int cpu
)
387 struct percpu_ida_cpu
*remote
;
388 if (cpu
== nr_cpu_ids
)
389 return pool
->nr_free
;
390 remote
= per_cpu_ptr(pool
->tag_cpu
, cpu
);
391 return remote
->nr_free
;
393 EXPORT_SYMBOL_GPL(percpu_ida_free_tags
);