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git.proxmox.com Git - mirror_ubuntu-eoan-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/init.h>
23 #include <linux/kernel.h>
24 #include <linux/percpu.h>
25 #include <linux/sched.h>
26 #include <linux/string.h>
27 #include <linux/spinlock.h>
28 #include <linux/percpu_ida.h>
30 struct percpu_ida_cpu
{
32 * Even though this is percpu, we need a lock for tag stealing by remote
37 /* nr_free/freelist form a stack of free IDs */
42 static inline void move_tags(unsigned *dst
, unsigned *dst_nr
,
43 unsigned *src
, unsigned *src_nr
,
47 memcpy(dst
+ *dst_nr
, src
+ *src_nr
, sizeof(unsigned) * nr
);
52 * Try to steal tags from a remote cpu's percpu freelist.
54 * We first check how many percpu freelists have tags
56 * Then we iterate through the cpus until we find some tags - we don't attempt
57 * to find the "best" cpu to steal from, to keep cacheline bouncing to a
60 static inline void steal_tags(struct percpu_ida
*pool
,
61 struct percpu_ida_cpu
*tags
)
63 unsigned cpus_have_tags
, cpu
= pool
->cpu_last_stolen
;
64 struct percpu_ida_cpu
*remote
;
66 for (cpus_have_tags
= cpumask_weight(&pool
->cpus_have_tags
);
67 cpus_have_tags
; cpus_have_tags
--) {
68 cpu
= cpumask_next(cpu
, &pool
->cpus_have_tags
);
70 if (cpu
>= nr_cpu_ids
) {
71 cpu
= cpumask_first(&pool
->cpus_have_tags
);
72 if (cpu
>= nr_cpu_ids
)
76 pool
->cpu_last_stolen
= cpu
;
77 remote
= per_cpu_ptr(pool
->tag_cpu
, cpu
);
79 cpumask_clear_cpu(cpu
, &pool
->cpus_have_tags
);
84 spin_lock(&remote
->lock
);
86 if (remote
->nr_free
) {
87 memcpy(tags
->freelist
,
89 sizeof(unsigned) * remote
->nr_free
);
91 tags
->nr_free
= remote
->nr_free
;
95 spin_unlock(&remote
->lock
);
103 * Pop up to IDA_PCPU_BATCH_MOVE IDs off the global freelist, and push them onto
104 * our percpu freelist:
106 static inline void alloc_global_tags(struct percpu_ida
*pool
,
107 struct percpu_ida_cpu
*tags
)
109 move_tags(tags
->freelist
, &tags
->nr_free
,
110 pool
->freelist
, &pool
->nr_free
,
111 min(pool
->nr_free
, pool
->percpu_batch_size
));
114 static inline unsigned alloc_local_tag(struct percpu_ida_cpu
*tags
)
118 spin_lock(&tags
->lock
);
120 tag
= tags
->freelist
[--tags
->nr_free
];
121 spin_unlock(&tags
->lock
);
127 * percpu_ida_alloc - allocate a tag
128 * @pool: pool to allocate from
129 * @state: task state for prepare_to_wait
131 * Returns a tag - an integer in the range [0..nr_tags) (passed to
132 * tag_pool_init()), or otherwise -ENOSPC on allocation failure.
134 * Safe to be called from interrupt context (assuming it isn't passed
135 * TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE, of course).
137 * @gfp indicates whether or not to wait until a free id is available (it's not
138 * used for internal memory allocations); thus if passed __GFP_RECLAIM we may sleep
139 * however long it takes until another thread frees an id (same semantics as a
142 * Will not fail if passed TASK_UNINTERRUPTIBLE | TASK_INTERRUPTIBLE.
144 int percpu_ida_alloc(struct percpu_ida
*pool
, int state
)
147 struct percpu_ida_cpu
*tags
;
151 local_irq_save(flags
);
152 tags
= this_cpu_ptr(pool
->tag_cpu
);
155 tag
= alloc_local_tag(tags
);
156 if (likely(tag
>= 0)) {
157 local_irq_restore(flags
);
162 spin_lock(&pool
->lock
);
165 * prepare_to_wait() must come before steal_tags(), in case
166 * percpu_ida_free() on another cpu flips a bit in
169 * global lock held and irqs disabled, don't need percpu lock
171 if (state
!= TASK_RUNNING
)
172 prepare_to_wait(&pool
->wait
, &wait
, state
);
175 alloc_global_tags(pool
, tags
);
177 steal_tags(pool
, tags
);
180 tag
= tags
->freelist
[--tags
->nr_free
];
182 cpumask_set_cpu(smp_processor_id(),
183 &pool
->cpus_have_tags
);
186 spin_unlock(&pool
->lock
);
187 local_irq_restore(flags
);
189 if (tag
>= 0 || state
== TASK_RUNNING
)
192 if (signal_pending_state(state
, current
)) {
199 local_irq_save(flags
);
200 tags
= this_cpu_ptr(pool
->tag_cpu
);
202 if (state
!= TASK_RUNNING
)
203 finish_wait(&pool
->wait
, &wait
);
207 EXPORT_SYMBOL_GPL(percpu_ida_alloc
);
210 * percpu_ida_free - free a tag
211 * @pool: pool @tag was allocated from
212 * @tag: a tag previously allocated with percpu_ida_alloc()
214 * Safe to be called from interrupt context.
216 void percpu_ida_free(struct percpu_ida
*pool
, unsigned tag
)
218 struct percpu_ida_cpu
*tags
;
222 BUG_ON(tag
>= pool
->nr_tags
);
224 local_irq_save(flags
);
225 tags
= this_cpu_ptr(pool
->tag_cpu
);
227 spin_lock(&tags
->lock
);
228 tags
->freelist
[tags
->nr_free
++] = tag
;
230 nr_free
= tags
->nr_free
;
231 spin_unlock(&tags
->lock
);
234 cpumask_set_cpu(smp_processor_id(),
235 &pool
->cpus_have_tags
);
236 wake_up(&pool
->wait
);
239 if (nr_free
== pool
->percpu_max_size
) {
240 spin_lock(&pool
->lock
);
243 * Global lock held and irqs disabled, don't need percpu
246 if (tags
->nr_free
== pool
->percpu_max_size
) {
247 move_tags(pool
->freelist
, &pool
->nr_free
,
248 tags
->freelist
, &tags
->nr_free
,
249 pool
->percpu_batch_size
);
251 wake_up(&pool
->wait
);
253 spin_unlock(&pool
->lock
);
256 local_irq_restore(flags
);
258 EXPORT_SYMBOL_GPL(percpu_ida_free
);
261 * percpu_ida_destroy - release a tag pool's resources
262 * @pool: pool to free
264 * Frees the resources allocated by percpu_ida_init().
266 void percpu_ida_destroy(struct percpu_ida
*pool
)
268 free_percpu(pool
->tag_cpu
);
269 free_pages((unsigned long) pool
->freelist
,
270 get_order(pool
->nr_tags
* sizeof(unsigned)));
272 EXPORT_SYMBOL_GPL(percpu_ida_destroy
);
275 * percpu_ida_init - initialize a percpu tag pool
276 * @pool: pool to initialize
277 * @nr_tags: number of tags that will be available for allocation
279 * Initializes @pool so that it can be used to allocate tags - integers in the
280 * range [0, nr_tags). Typically, they'll be used by driver code to refer to a
281 * preallocated array of tag structures.
283 * Allocation is percpu, but sharding is limited by nr_tags - for best
284 * performance, the workload should not span more cpus than nr_tags / 128.
286 int __percpu_ida_init(struct percpu_ida
*pool
, unsigned long nr_tags
,
287 unsigned long max_size
, unsigned long batch_size
)
289 unsigned i
, cpu
, order
;
291 memset(pool
, 0, sizeof(*pool
));
293 init_waitqueue_head(&pool
->wait
);
294 spin_lock_init(&pool
->lock
);
295 pool
->nr_tags
= nr_tags
;
296 pool
->percpu_max_size
= max_size
;
297 pool
->percpu_batch_size
= batch_size
;
299 /* Guard against overflow */
300 if (nr_tags
> (unsigned) INT_MAX
+ 1) {
301 pr_err("percpu_ida_init(): nr_tags too large\n");
305 order
= get_order(nr_tags
* sizeof(unsigned));
306 pool
->freelist
= (void *) __get_free_pages(GFP_KERNEL
, order
);
310 for (i
= 0; i
< nr_tags
; i
++)
311 pool
->freelist
[i
] = i
;
313 pool
->nr_free
= nr_tags
;
315 pool
->tag_cpu
= __alloc_percpu(sizeof(struct percpu_ida_cpu
) +
316 pool
->percpu_max_size
* sizeof(unsigned),
321 for_each_possible_cpu(cpu
)
322 spin_lock_init(&per_cpu_ptr(pool
->tag_cpu
, cpu
)->lock
);
326 percpu_ida_destroy(pool
);
329 EXPORT_SYMBOL_GPL(__percpu_ida_init
);
332 * percpu_ida_for_each_free - iterate free ids of a pool
333 * @pool: pool to iterate
334 * @fn: interate callback function
335 * @data: parameter for @fn
337 * Note, this doesn't guarantee to iterate all free ids restrictly. Some free
338 * ids might be missed, some might be iterated duplicated, and some might
339 * be iterated and not free soon.
341 int percpu_ida_for_each_free(struct percpu_ida
*pool
, percpu_ida_cb fn
,
345 struct percpu_ida_cpu
*remote
;
346 unsigned cpu
, i
, err
= 0;
348 local_irq_save(flags
);
349 for_each_possible_cpu(cpu
) {
350 remote
= per_cpu_ptr(pool
->tag_cpu
, cpu
);
351 spin_lock(&remote
->lock
);
352 for (i
= 0; i
< remote
->nr_free
; i
++) {
353 err
= fn(remote
->freelist
[i
], data
);
357 spin_unlock(&remote
->lock
);
362 spin_lock(&pool
->lock
);
363 for (i
= 0; i
< pool
->nr_free
; i
++) {
364 err
= fn(pool
->freelist
[i
], data
);
368 spin_unlock(&pool
->lock
);
370 local_irq_restore(flags
);
373 EXPORT_SYMBOL_GPL(percpu_ida_for_each_free
);
376 * percpu_ida_free_tags - return free tags number of a specific cpu or global pool
377 * @pool: pool related
378 * @cpu: specific cpu or global pool if @cpu == nr_cpu_ids
380 * Note: this just returns a snapshot of free tags number.
382 unsigned percpu_ida_free_tags(struct percpu_ida
*pool
, int cpu
)
384 struct percpu_ida_cpu
*remote
;
385 if (cpu
== nr_cpu_ids
)
386 return pool
->nr_free
;
387 remote
= per_cpu_ptr(pool
->tag_cpu
, cpu
);
388 return remote
->nr_free
;
390 EXPORT_SYMBOL_GPL(percpu_ida_free_tags
);