2 * Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
3 * Copyright (C) 2007 The Regents of the University of California.
4 * Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
5 * Written by Brian Behlendorf <behlendorf1@llnl.gov>.
8 * This file is part of the SPL, Solaris Porting Layer.
10 * The SPL is free software; you can redistribute it and/or modify it
11 * under the terms of the GNU General Public License as published by the
12 * Free Software Foundation; either version 2 of the License, or (at your
13 * option) any later version.
15 * The SPL is distributed in the hope that it will be useful, but WITHOUT
16 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
17 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
20 * You should have received a copy of the GNU General Public License along
21 * with the SPL. If not, see <http://www.gnu.org/licenses/>.
24 #include <linux/percpu_compat.h>
26 #include <sys/kmem_cache.h>
27 #include <sys/taskq.h>
28 #include <sys/timer.h>
31 #include <linux/slab.h>
32 #include <linux/swap.h>
33 #include <linux/prefetch.h>
36 * Within the scope of spl-kmem.c file the kmem_cache_* definitions
37 * are removed to allow access to the real Linux slab allocator.
39 #undef kmem_cache_destroy
40 #undef kmem_cache_create
41 #undef kmem_cache_alloc
42 #undef kmem_cache_free
46 * Linux 3.16 replaced smp_mb__{before,after}_{atomic,clear}_{dec,inc,bit}()
47 * with smp_mb__{before,after}_atomic() because they were redundant. This is
48 * only used inside our SLAB allocator, so we implement an internal wrapper
49 * here to give us smp_mb__{before,after}_atomic() on older kernels.
51 #ifndef smp_mb__before_atomic
52 #define smp_mb__before_atomic(x) smp_mb__before_clear_bit(x)
55 #ifndef smp_mb__after_atomic
56 #define smp_mb__after_atomic(x) smp_mb__after_clear_bit(x)
62 * Cache magazines are an optimization designed to minimize the cost of
63 * allocating memory. They do this by keeping a per-cpu cache of recently
64 * freed objects, which can then be reallocated without taking a lock. This
65 * can improve performance on highly contended caches. However, because
66 * objects in magazines will prevent otherwise empty slabs from being
67 * immediately released this may not be ideal for low memory machines.
69 * For this reason spl_kmem_cache_magazine_size can be used to set a maximum
70 * magazine size. When this value is set to 0 the magazine size will be
71 * automatically determined based on the object size. Otherwise magazines
72 * will be limited to 2-256 objects per magazine (i.e per cpu). Magazines
73 * may never be entirely disabled in this implementation.
75 unsigned int spl_kmem_cache_magazine_size = 0;
76 module_param(spl_kmem_cache_magazine_size, uint, 0444);
77 MODULE_PARM_DESC(spl_kmem_cache_magazine_size,
78 "Default magazine size (2-256), set automatically (0)");
81 * The default behavior is to report the number of objects remaining in the
82 * cache. This allows the Linux VM to repeatedly reclaim objects from the
83 * cache when memory is low satisfy other memory allocations. Alternately,
84 * setting this value to KMC_RECLAIM_ONCE limits how aggressively the cache
85 * is reclaimed. This may increase the likelihood of out of memory events.
87 unsigned int spl_kmem_cache_reclaim = 0 /* KMC_RECLAIM_ONCE */;
88 module_param(spl_kmem_cache_reclaim, uint, 0644);
89 MODULE_PARM_DESC(spl_kmem_cache_reclaim, "Single reclaim pass (0x1)");
91 unsigned int spl_kmem_cache_obj_per_slab = SPL_KMEM_CACHE_OBJ_PER_SLAB;
92 module_param(spl_kmem_cache_obj_per_slab, uint, 0644);
93 MODULE_PARM_DESC(spl_kmem_cache_obj_per_slab, "Number of objects per slab");
95 unsigned int spl_kmem_cache_max_size = SPL_KMEM_CACHE_MAX_SIZE;
96 module_param(spl_kmem_cache_max_size, uint, 0644);
97 MODULE_PARM_DESC(spl_kmem_cache_max_size, "Maximum size of slab in MB");
100 * For small objects the Linux slab allocator should be used to make the most
101 * efficient use of the memory. However, large objects are not supported by
102 * the Linux slab and therefore the SPL implementation is preferred. A cutoff
103 * of 16K was determined to be optimal for architectures using 4K pages.
105 #if PAGE_SIZE == 4096
106 unsigned int spl_kmem_cache_slab_limit = 16384;
108 unsigned int spl_kmem_cache_slab_limit = 0;
110 module_param(spl_kmem_cache_slab_limit, uint, 0644);
111 MODULE_PARM_DESC(spl_kmem_cache_slab_limit,
112 "Objects less than N bytes use the Linux slab");
115 * The number of threads available to allocate new slabs for caches. This
116 * should not need to be tuned but it is available for performance analysis.
118 unsigned int spl_kmem_cache_kmem_threads = 4;
119 module_param(spl_kmem_cache_kmem_threads, uint, 0444);
120 MODULE_PARM_DESC(spl_kmem_cache_kmem_threads,
121 "Number of spl_kmem_cache threads");
125 * Slab allocation interfaces
127 * While the Linux slab implementation was inspired by the Solaris
128 * implementation I cannot use it to emulate the Solaris APIs. I
129 * require two features which are not provided by the Linux slab.
131 * 1) Constructors AND destructors. Recent versions of the Linux
132 * kernel have removed support for destructors. This is a deal
133 * breaker for the SPL which contains particularly expensive
134 * initializers for mutex's, condition variables, etc. We also
135 * require a minimal level of cleanup for these data types unlike
136 * many Linux data types which do need to be explicitly destroyed.
138 * 2) Virtual address space backed slab. Callers of the Solaris slab
139 * expect it to work well for both small are very large allocations.
140 * Because of memory fragmentation the Linux slab which is backed
141 * by kmalloc'ed memory performs very badly when confronted with
142 * large numbers of large allocations. Basing the slab on the
143 * virtual address space removes the need for contiguous pages
144 * and greatly improve performance for large allocations.
146 * For these reasons, the SPL has its own slab implementation with
147 * the needed features. It is not as highly optimized as either the
148 * Solaris or Linux slabs, but it should get me most of what is
149 * needed until it can be optimized or obsoleted by another approach.
151 * One serious concern I do have about this method is the relatively
152 * small virtual address space on 32bit arches. This will seriously
153 * constrain the size of the slab caches and their performance.
156 struct list_head spl_kmem_cache_list; /* List of caches */
157 struct rw_semaphore spl_kmem_cache_sem; /* Cache list lock */
158 taskq_t *spl_kmem_cache_taskq; /* Task queue for aging / reclaim */
160 static void spl_cache_shrink(spl_kmem_cache_t *skc, void *obj);
163 kv_alloc(spl_kmem_cache_t *skc, int size, int flags)
165 gfp_t lflags = kmem_flags_convert(flags);
168 ptr = spl_vmalloc(size, lflags | __GFP_HIGHMEM);
170 /* Resulting allocated memory will be page aligned */
171 ASSERT(IS_P2ALIGNED(ptr, PAGE_SIZE));
177 kv_free(spl_kmem_cache_t *skc, void *ptr, int size)
179 ASSERT(IS_P2ALIGNED(ptr, PAGE_SIZE));
182 * The Linux direct reclaim path uses this out of band value to
183 * determine if forward progress is being made. Normally this is
184 * incremented by kmem_freepages() which is part of the various
185 * Linux slab implementations. However, since we are using none
186 * of that infrastructure we are responsible for incrementing it.
188 if (current->reclaim_state)
189 current->reclaim_state->reclaimed_slab += size >> PAGE_SHIFT;
195 * Required space for each aligned sks.
197 static inline uint32_t
198 spl_sks_size(spl_kmem_cache_t *skc)
200 return (P2ROUNDUP_TYPED(sizeof (spl_kmem_slab_t),
201 skc->skc_obj_align, uint32_t));
205 * Required space for each aligned object.
207 static inline uint32_t
208 spl_obj_size(spl_kmem_cache_t *skc)
210 uint32_t align = skc->skc_obj_align;
212 return (P2ROUNDUP_TYPED(skc->skc_obj_size, align, uint32_t) +
213 P2ROUNDUP_TYPED(sizeof (spl_kmem_obj_t), align, uint32_t));
217 spl_kmem_cache_inuse(kmem_cache_t *cache)
219 return (cache->skc_obj_total);
221 EXPORT_SYMBOL(spl_kmem_cache_inuse);
224 spl_kmem_cache_entry_size(kmem_cache_t *cache)
226 return (cache->skc_obj_size);
228 EXPORT_SYMBOL(spl_kmem_cache_entry_size);
231 * Lookup the spl_kmem_object_t for an object given that object.
233 static inline spl_kmem_obj_t *
234 spl_sko_from_obj(spl_kmem_cache_t *skc, void *obj)
236 return (obj + P2ROUNDUP_TYPED(skc->skc_obj_size,
237 skc->skc_obj_align, uint32_t));
241 * It's important that we pack the spl_kmem_obj_t structure and the
242 * actual objects in to one large address space to minimize the number
243 * of calls to the allocator. It is far better to do a few large
244 * allocations and then subdivide it ourselves. Now which allocator
245 * we use requires balancing a few trade offs.
247 * For small objects we use kmem_alloc() because as long as you are
248 * only requesting a small number of pages (ideally just one) its cheap.
249 * However, when you start requesting multiple pages with kmem_alloc()
250 * it gets increasingly expensive since it requires contiguous pages.
251 * For this reason we shift to vmem_alloc() for slabs of large objects
252 * which removes the need for contiguous pages. We do not use
253 * vmem_alloc() in all cases because there is significant locking
254 * overhead in __get_vm_area_node(). This function takes a single
255 * global lock when acquiring an available virtual address range which
256 * serializes all vmem_alloc()'s for all slab caches. Using slightly
257 * different allocation functions for small and large objects should
258 * give us the best of both worlds.
260 * +------------------------+
261 * | spl_kmem_slab_t --+-+ |
262 * | skc_obj_size <-+ | |
263 * | spl_kmem_obj_t | |
264 * | skc_obj_size <---+ |
265 * | spl_kmem_obj_t | |
267 * +------------------------+
269 static spl_kmem_slab_t *
270 spl_slab_alloc(spl_kmem_cache_t *skc, int flags)
272 spl_kmem_slab_t *sks;
276 base = kv_alloc(skc, skc->skc_slab_size, flags);
280 sks = (spl_kmem_slab_t *)base;
281 sks->sks_magic = SKS_MAGIC;
282 sks->sks_objs = skc->skc_slab_objs;
283 sks->sks_age = jiffies;
284 sks->sks_cache = skc;
285 INIT_LIST_HEAD(&sks->sks_list);
286 INIT_LIST_HEAD(&sks->sks_free_list);
288 obj_size = spl_obj_size(skc);
290 for (int i = 0; i < sks->sks_objs; i++) {
291 void *obj = base + spl_sks_size(skc) + (i * obj_size);
293 ASSERT(IS_P2ALIGNED(obj, skc->skc_obj_align));
294 spl_kmem_obj_t *sko = spl_sko_from_obj(skc, obj);
296 sko->sko_magic = SKO_MAGIC;
298 INIT_LIST_HEAD(&sko->sko_list);
299 list_add_tail(&sko->sko_list, &sks->sks_free_list);
306 * Remove a slab from complete or partial list, it must be called with
307 * the 'skc->skc_lock' held but the actual free must be performed
308 * outside the lock to prevent deadlocking on vmem addresses.
311 spl_slab_free(spl_kmem_slab_t *sks,
312 struct list_head *sks_list, struct list_head *sko_list)
314 spl_kmem_cache_t *skc;
316 ASSERT(sks->sks_magic == SKS_MAGIC);
317 ASSERT(sks->sks_ref == 0);
319 skc = sks->sks_cache;
320 ASSERT(skc->skc_magic == SKC_MAGIC);
323 * Update slab/objects counters in the cache, then remove the
324 * slab from the skc->skc_partial_list. Finally add the slab
325 * and all its objects in to the private work lists where the
326 * destructors will be called and the memory freed to the system.
328 skc->skc_obj_total -= sks->sks_objs;
329 skc->skc_slab_total--;
330 list_del(&sks->sks_list);
331 list_add(&sks->sks_list, sks_list);
332 list_splice_init(&sks->sks_free_list, sko_list);
336 * Reclaim empty slabs at the end of the partial list.
339 spl_slab_reclaim(spl_kmem_cache_t *skc)
341 spl_kmem_slab_t *sks = NULL, *m = NULL;
342 spl_kmem_obj_t *sko = NULL, *n = NULL;
347 * Empty slabs and objects must be moved to a private list so they
348 * can be safely freed outside the spin lock. All empty slabs are
349 * at the end of skc->skc_partial_list, therefore once a non-empty
350 * slab is found we can stop scanning.
352 spin_lock(&skc->skc_lock);
353 list_for_each_entry_safe_reverse(sks, m,
354 &skc->skc_partial_list, sks_list) {
356 if (sks->sks_ref > 0)
359 spl_slab_free(sks, &sks_list, &sko_list);
361 spin_unlock(&skc->skc_lock);
364 * The following two loops ensure all the object destructors are run,
365 * and the slabs themselves are freed. This is all done outside the
366 * skc->skc_lock since this allows the destructor to sleep, and
367 * allows us to perform a conditional reschedule when a freeing a
368 * large number of objects and slabs back to the system.
371 list_for_each_entry_safe(sko, n, &sko_list, sko_list) {
372 ASSERT(sko->sko_magic == SKO_MAGIC);
375 list_for_each_entry_safe(sks, m, &sks_list, sks_list) {
376 ASSERT(sks->sks_magic == SKS_MAGIC);
377 kv_free(skc, sks, skc->skc_slab_size);
381 static spl_kmem_emergency_t *
382 spl_emergency_search(struct rb_root *root, void *obj)
384 struct rb_node *node = root->rb_node;
385 spl_kmem_emergency_t *ske;
386 unsigned long address = (unsigned long)obj;
389 ske = container_of(node, spl_kmem_emergency_t, ske_node);
391 if (address < ske->ske_obj)
392 node = node->rb_left;
393 else if (address > ske->ske_obj)
394 node = node->rb_right;
403 spl_emergency_insert(struct rb_root *root, spl_kmem_emergency_t *ske)
405 struct rb_node **new = &(root->rb_node), *parent = NULL;
406 spl_kmem_emergency_t *ske_tmp;
407 unsigned long address = ske->ske_obj;
410 ske_tmp = container_of(*new, spl_kmem_emergency_t, ske_node);
413 if (address < ske_tmp->ske_obj)
414 new = &((*new)->rb_left);
415 else if (address > ske_tmp->ske_obj)
416 new = &((*new)->rb_right);
421 rb_link_node(&ske->ske_node, parent, new);
422 rb_insert_color(&ske->ske_node, root);
428 * Allocate a single emergency object and track it in a red black tree.
431 spl_emergency_alloc(spl_kmem_cache_t *skc, int flags, void **obj)
433 gfp_t lflags = kmem_flags_convert(flags);
434 spl_kmem_emergency_t *ske;
435 int order = get_order(skc->skc_obj_size);
438 /* Last chance use a partial slab if one now exists */
439 spin_lock(&skc->skc_lock);
440 empty = list_empty(&skc->skc_partial_list);
441 spin_unlock(&skc->skc_lock);
445 ske = kmalloc(sizeof (*ske), lflags);
449 ske->ske_obj = __get_free_pages(lflags, order);
450 if (ske->ske_obj == 0) {
455 spin_lock(&skc->skc_lock);
456 empty = spl_emergency_insert(&skc->skc_emergency_tree, ske);
458 skc->skc_obj_total++;
459 skc->skc_obj_emergency++;
460 if (skc->skc_obj_emergency > skc->skc_obj_emergency_max)
461 skc->skc_obj_emergency_max = skc->skc_obj_emergency;
463 spin_unlock(&skc->skc_lock);
465 if (unlikely(!empty)) {
466 free_pages(ske->ske_obj, order);
471 *obj = (void *)ske->ske_obj;
477 * Locate the passed object in the red black tree and free it.
480 spl_emergency_free(spl_kmem_cache_t *skc, void *obj)
482 spl_kmem_emergency_t *ske;
483 int order = get_order(skc->skc_obj_size);
485 spin_lock(&skc->skc_lock);
486 ske = spl_emergency_search(&skc->skc_emergency_tree, obj);
488 rb_erase(&ske->ske_node, &skc->skc_emergency_tree);
489 skc->skc_obj_emergency--;
490 skc->skc_obj_total--;
492 spin_unlock(&skc->skc_lock);
497 free_pages(ske->ske_obj, order);
504 * Release objects from the per-cpu magazine back to their slab. The flush
505 * argument contains the max number of entries to remove from the magazine.
508 spl_cache_flush(spl_kmem_cache_t *skc, spl_kmem_magazine_t *skm, int flush)
510 spin_lock(&skc->skc_lock);
512 ASSERT(skc->skc_magic == SKC_MAGIC);
513 ASSERT(skm->skm_magic == SKM_MAGIC);
515 int count = MIN(flush, skm->skm_avail);
516 for (int i = 0; i < count; i++)
517 spl_cache_shrink(skc, skm->skm_objs[i]);
519 skm->skm_avail -= count;
520 memmove(skm->skm_objs, &(skm->skm_objs[count]),
521 sizeof (void *) * skm->skm_avail);
523 spin_unlock(&skc->skc_lock);
527 * Size a slab based on the size of each aligned object plus spl_kmem_obj_t.
528 * When on-slab we want to target spl_kmem_cache_obj_per_slab. However,
529 * for very small objects we may end up with more than this so as not
530 * to waste space in the minimal allocation of a single page. Also for
531 * very large objects we may use as few as spl_kmem_cache_obj_per_slab_min,
532 * lower than this and we will fail.
535 spl_slab_size(spl_kmem_cache_t *skc, uint32_t *objs, uint32_t *size)
537 uint32_t sks_size, obj_size, max_size, tgt_size, tgt_objs;
539 sks_size = spl_sks_size(skc);
540 obj_size = spl_obj_size(skc);
541 max_size = (spl_kmem_cache_max_size * 1024 * 1024);
542 tgt_size = (spl_kmem_cache_obj_per_slab * obj_size + sks_size);
544 if (tgt_size <= max_size) {
545 tgt_objs = (tgt_size - sks_size) / obj_size;
547 tgt_objs = (max_size - sks_size) / obj_size;
548 tgt_size = (tgt_objs * obj_size) + sks_size;
561 * Make a guess at reasonable per-cpu magazine size based on the size of
562 * each object and the cost of caching N of them in each magazine. Long
563 * term this should really adapt based on an observed usage heuristic.
566 spl_magazine_size(spl_kmem_cache_t *skc)
568 uint32_t obj_size = spl_obj_size(skc);
571 if (spl_kmem_cache_magazine_size > 0)
572 return (MAX(MIN(spl_kmem_cache_magazine_size, 256), 2));
574 /* Per-magazine sizes below assume a 4Kib page size */
575 if (obj_size > (PAGE_SIZE * 256))
576 size = 4; /* Minimum 4Mib per-magazine */
577 else if (obj_size > (PAGE_SIZE * 32))
578 size = 16; /* Minimum 2Mib per-magazine */
579 else if (obj_size > (PAGE_SIZE))
580 size = 64; /* Minimum 256Kib per-magazine */
581 else if (obj_size > (PAGE_SIZE / 4))
582 size = 128; /* Minimum 128Kib per-magazine */
590 * Allocate a per-cpu magazine to associate with a specific core.
592 static spl_kmem_magazine_t *
593 spl_magazine_alloc(spl_kmem_cache_t *skc, int cpu)
595 spl_kmem_magazine_t *skm;
596 int size = sizeof (spl_kmem_magazine_t) +
597 sizeof (void *) * skc->skc_mag_size;
599 skm = kmalloc_node(size, GFP_KERNEL, cpu_to_node(cpu));
601 skm->skm_magic = SKM_MAGIC;
603 skm->skm_size = skc->skc_mag_size;
604 skm->skm_refill = skc->skc_mag_refill;
605 skm->skm_cache = skc;
613 * Free a per-cpu magazine associated with a specific core.
616 spl_magazine_free(spl_kmem_magazine_t *skm)
618 ASSERT(skm->skm_magic == SKM_MAGIC);
619 ASSERT(skm->skm_avail == 0);
624 * Create all pre-cpu magazines of reasonable sizes.
627 spl_magazine_create(spl_kmem_cache_t *skc)
631 ASSERT((skc->skc_flags & KMC_SLAB) == 0);
633 skc->skc_mag = kzalloc(sizeof (spl_kmem_magazine_t *) *
634 num_possible_cpus(), kmem_flags_convert(KM_SLEEP));
635 skc->skc_mag_size = spl_magazine_size(skc);
636 skc->skc_mag_refill = (skc->skc_mag_size + 1) / 2;
638 for_each_possible_cpu(i) {
639 skc->skc_mag[i] = spl_magazine_alloc(skc, i);
640 if (!skc->skc_mag[i]) {
641 for (i--; i >= 0; i--)
642 spl_magazine_free(skc->skc_mag[i]);
653 * Destroy all pre-cpu magazines.
656 spl_magazine_destroy(spl_kmem_cache_t *skc)
658 spl_kmem_magazine_t *skm;
661 ASSERT((skc->skc_flags & KMC_SLAB) == 0);
663 for_each_possible_cpu(i) {
664 skm = skc->skc_mag[i];
665 spl_cache_flush(skc, skm, skm->skm_avail);
666 spl_magazine_free(skm);
673 * Create a object cache based on the following arguments:
675 * size cache object size
676 * align cache object alignment
677 * ctor cache object constructor
678 * dtor cache object destructor
679 * reclaim cache object reclaim
680 * priv cache private data for ctor/dtor/reclaim
681 * vmp unused must be NULL
683 * KMC_KVMEM Force kvmem backed SPL cache
684 * KMC_SLAB Force Linux slab backed cache
685 * KMC_NODEBUG Disable debugging (unsupported)
688 spl_kmem_cache_create(char *name, size_t size, size_t align,
689 spl_kmem_ctor_t ctor, spl_kmem_dtor_t dtor, void *reclaim,
690 void *priv, void *vmp, int flags)
692 gfp_t lflags = kmem_flags_convert(KM_SLEEP);
693 spl_kmem_cache_t *skc;
700 ASSERT(reclaim == NULL);
704 skc = kzalloc(sizeof (*skc), lflags);
708 skc->skc_magic = SKC_MAGIC;
709 skc->skc_name_size = strlen(name) + 1;
710 skc->skc_name = (char *)kmalloc(skc->skc_name_size, lflags);
711 if (skc->skc_name == NULL) {
715 strncpy(skc->skc_name, name, skc->skc_name_size);
717 skc->skc_ctor = ctor;
718 skc->skc_dtor = dtor;
719 skc->skc_private = priv;
721 skc->skc_linux_cache = NULL;
722 skc->skc_flags = flags;
723 skc->skc_obj_size = size;
724 skc->skc_obj_align = SPL_KMEM_CACHE_ALIGN;
725 atomic_set(&skc->skc_ref, 0);
727 INIT_LIST_HEAD(&skc->skc_list);
728 INIT_LIST_HEAD(&skc->skc_complete_list);
729 INIT_LIST_HEAD(&skc->skc_partial_list);
730 skc->skc_emergency_tree = RB_ROOT;
731 spin_lock_init(&skc->skc_lock);
732 init_waitqueue_head(&skc->skc_waitq);
733 skc->skc_slab_fail = 0;
734 skc->skc_slab_create = 0;
735 skc->skc_slab_destroy = 0;
736 skc->skc_slab_total = 0;
737 skc->skc_slab_alloc = 0;
738 skc->skc_slab_max = 0;
739 skc->skc_obj_total = 0;
740 skc->skc_obj_alloc = 0;
741 skc->skc_obj_max = 0;
742 skc->skc_obj_deadlock = 0;
743 skc->skc_obj_emergency = 0;
744 skc->skc_obj_emergency_max = 0;
746 rc = percpu_counter_init_common(&skc->skc_linux_alloc, 0,
754 * Verify the requested alignment restriction is sane.
758 VERIFY3U(align, >=, SPL_KMEM_CACHE_ALIGN);
759 VERIFY3U(align, <=, PAGE_SIZE);
760 skc->skc_obj_align = align;
764 * When no specific type of slab is requested (kmem, vmem, or
765 * linuxslab) then select a cache type based on the object size
766 * and default tunables.
768 if (!(skc->skc_flags & (KMC_SLAB | KMC_KVMEM))) {
769 if (spl_kmem_cache_slab_limit &&
770 size <= (size_t)spl_kmem_cache_slab_limit) {
772 * Objects smaller than spl_kmem_cache_slab_limit can
773 * use the Linux slab for better space-efficiency.
775 skc->skc_flags |= KMC_SLAB;
778 * All other objects are considered large and are
779 * placed on kvmem backed slabs.
781 skc->skc_flags |= KMC_KVMEM;
786 * Given the type of slab allocate the required resources.
788 if (skc->skc_flags & KMC_KVMEM) {
789 rc = spl_slab_size(skc,
790 &skc->skc_slab_objs, &skc->skc_slab_size);
794 rc = spl_magazine_create(skc);
798 unsigned long slabflags = 0;
800 if (size > (SPL_MAX_KMEM_ORDER_NR_PAGES * PAGE_SIZE)) {
805 #if defined(SLAB_USERCOPY)
807 * Required for PAX-enabled kernels if the slab is to be
808 * used for copying between user and kernel space.
810 slabflags |= SLAB_USERCOPY;
813 #if defined(HAVE_KMEM_CACHE_CREATE_USERCOPY)
815 * Newer grsec patchset uses kmem_cache_create_usercopy()
816 * instead of SLAB_USERCOPY flag
818 skc->skc_linux_cache = kmem_cache_create_usercopy(
819 skc->skc_name, size, align, slabflags, 0, size, NULL);
821 skc->skc_linux_cache = kmem_cache_create(
822 skc->skc_name, size, align, slabflags, NULL);
824 if (skc->skc_linux_cache == NULL) {
830 down_write(&spl_kmem_cache_sem);
831 list_add_tail(&skc->skc_list, &spl_kmem_cache_list);
832 up_write(&spl_kmem_cache_sem);
836 kfree(skc->skc_name);
837 percpu_counter_destroy(&skc->skc_linux_alloc);
841 EXPORT_SYMBOL(spl_kmem_cache_create);
844 * Register a move callback for cache defragmentation.
845 * XXX: Unimplemented but harmless to stub out for now.
848 spl_kmem_cache_set_move(spl_kmem_cache_t *skc,
849 kmem_cbrc_t (move)(void *, void *, size_t, void *))
851 ASSERT(move != NULL);
853 EXPORT_SYMBOL(spl_kmem_cache_set_move);
856 * Destroy a cache and all objects associated with the cache.
859 spl_kmem_cache_destroy(spl_kmem_cache_t *skc)
861 DECLARE_WAIT_QUEUE_HEAD(wq);
864 ASSERT(skc->skc_magic == SKC_MAGIC);
865 ASSERT(skc->skc_flags & (KMC_KVMEM | KMC_SLAB));
867 down_write(&spl_kmem_cache_sem);
868 list_del_init(&skc->skc_list);
869 up_write(&spl_kmem_cache_sem);
871 /* Cancel any and wait for any pending delayed tasks */
872 VERIFY(!test_and_set_bit(KMC_BIT_DESTROY, &skc->skc_flags));
874 spin_lock(&skc->skc_lock);
875 id = skc->skc_taskqid;
876 spin_unlock(&skc->skc_lock);
878 taskq_cancel_id(spl_kmem_cache_taskq, id);
881 * Wait until all current callers complete, this is mainly
882 * to catch the case where a low memory situation triggers a
883 * cache reaping action which races with this destroy.
885 wait_event(wq, atomic_read(&skc->skc_ref) == 0);
887 if (skc->skc_flags & KMC_KVMEM) {
888 spl_magazine_destroy(skc);
889 spl_slab_reclaim(skc);
891 ASSERT(skc->skc_flags & KMC_SLAB);
892 kmem_cache_destroy(skc->skc_linux_cache);
895 spin_lock(&skc->skc_lock);
898 * Validate there are no objects in use and free all the
899 * spl_kmem_slab_t, spl_kmem_obj_t, and object buffers.
901 ASSERT3U(skc->skc_slab_alloc, ==, 0);
902 ASSERT3U(skc->skc_obj_alloc, ==, 0);
903 ASSERT3U(skc->skc_slab_total, ==, 0);
904 ASSERT3U(skc->skc_obj_total, ==, 0);
905 ASSERT3U(skc->skc_obj_emergency, ==, 0);
906 ASSERT(list_empty(&skc->skc_complete_list));
908 ASSERT3U(percpu_counter_sum(&skc->skc_linux_alloc), ==, 0);
909 percpu_counter_destroy(&skc->skc_linux_alloc);
911 spin_unlock(&skc->skc_lock);
913 kfree(skc->skc_name);
916 EXPORT_SYMBOL(spl_kmem_cache_destroy);
919 * Allocate an object from a slab attached to the cache. This is used to
920 * repopulate the per-cpu magazine caches in batches when they run low.
923 spl_cache_obj(spl_kmem_cache_t *skc, spl_kmem_slab_t *sks)
927 ASSERT(skc->skc_magic == SKC_MAGIC);
928 ASSERT(sks->sks_magic == SKS_MAGIC);
930 sko = list_entry(sks->sks_free_list.next, spl_kmem_obj_t, sko_list);
931 ASSERT(sko->sko_magic == SKO_MAGIC);
932 ASSERT(sko->sko_addr != NULL);
934 /* Remove from sks_free_list */
935 list_del_init(&sko->sko_list);
937 sks->sks_age = jiffies;
939 skc->skc_obj_alloc++;
941 /* Track max obj usage statistics */
942 if (skc->skc_obj_alloc > skc->skc_obj_max)
943 skc->skc_obj_max = skc->skc_obj_alloc;
945 /* Track max slab usage statistics */
946 if (sks->sks_ref == 1) {
947 skc->skc_slab_alloc++;
949 if (skc->skc_slab_alloc > skc->skc_slab_max)
950 skc->skc_slab_max = skc->skc_slab_alloc;
953 return (sko->sko_addr);
957 * Generic slab allocation function to run by the global work queues.
958 * It is responsible for allocating a new slab, linking it in to the list
959 * of partial slabs, and then waking any waiters.
962 __spl_cache_grow(spl_kmem_cache_t *skc, int flags)
964 spl_kmem_slab_t *sks;
966 fstrans_cookie_t cookie = spl_fstrans_mark();
967 sks = spl_slab_alloc(skc, flags);
968 spl_fstrans_unmark(cookie);
970 spin_lock(&skc->skc_lock);
972 skc->skc_slab_total++;
973 skc->skc_obj_total += sks->sks_objs;
974 list_add_tail(&sks->sks_list, &skc->skc_partial_list);
976 smp_mb__before_atomic();
977 clear_bit(KMC_BIT_DEADLOCKED, &skc->skc_flags);
978 smp_mb__after_atomic();
980 spin_unlock(&skc->skc_lock);
982 return (sks == NULL ? -ENOMEM : 0);
986 spl_cache_grow_work(void *data)
988 spl_kmem_alloc_t *ska = (spl_kmem_alloc_t *)data;
989 spl_kmem_cache_t *skc = ska->ska_cache;
991 int error = __spl_cache_grow(skc, ska->ska_flags);
993 atomic_dec(&skc->skc_ref);
994 smp_mb__before_atomic();
995 clear_bit(KMC_BIT_GROWING, &skc->skc_flags);
996 smp_mb__after_atomic();
998 wake_up_all(&skc->skc_waitq);
1004 * Returns non-zero when a new slab should be available.
1007 spl_cache_grow_wait(spl_kmem_cache_t *skc)
1009 return (!test_bit(KMC_BIT_GROWING, &skc->skc_flags));
1013 * No available objects on any slabs, create a new slab. Note that this
1014 * functionality is disabled for KMC_SLAB caches which are backed by the
1018 spl_cache_grow(spl_kmem_cache_t *skc, int flags, void **obj)
1020 int remaining, rc = 0;
1022 ASSERT0(flags & ~KM_PUBLIC_MASK);
1023 ASSERT(skc->skc_magic == SKC_MAGIC);
1024 ASSERT((skc->skc_flags & KMC_SLAB) == 0);
1029 * Before allocating a new slab wait for any reaping to complete and
1030 * then return so the local magazine can be rechecked for new objects.
1032 if (test_bit(KMC_BIT_REAPING, &skc->skc_flags)) {
1033 rc = spl_wait_on_bit(&skc->skc_flags, KMC_BIT_REAPING,
1034 TASK_UNINTERRUPTIBLE);
1035 return (rc ? rc : -EAGAIN);
1039 * Note: It would be nice to reduce the overhead of context switch
1040 * and improve NUMA locality, by trying to allocate a new slab in the
1041 * current process context with KM_NOSLEEP flag.
1043 * However, this can't be applied to vmem/kvmem due to a bug that
1044 * spl_vmalloc() doesn't honor gfp flags in page table allocation.
1048 * This is handled by dispatching a work request to the global work
1049 * queue. This allows us to asynchronously allocate a new slab while
1050 * retaining the ability to safely fall back to a smaller synchronous
1051 * allocations to ensure forward progress is always maintained.
1053 if (test_and_set_bit(KMC_BIT_GROWING, &skc->skc_flags) == 0) {
1054 spl_kmem_alloc_t *ska;
1056 ska = kmalloc(sizeof (*ska), kmem_flags_convert(flags));
1058 clear_bit_unlock(KMC_BIT_GROWING, &skc->skc_flags);
1059 smp_mb__after_atomic();
1060 wake_up_all(&skc->skc_waitq);
1064 atomic_inc(&skc->skc_ref);
1065 ska->ska_cache = skc;
1066 ska->ska_flags = flags;
1067 taskq_init_ent(&ska->ska_tqe);
1068 taskq_dispatch_ent(spl_kmem_cache_taskq,
1069 spl_cache_grow_work, ska, 0, &ska->ska_tqe);
1073 * The goal here is to only detect the rare case where a virtual slab
1074 * allocation has deadlocked. We must be careful to minimize the use
1075 * of emergency objects which are more expensive to track. Therefore,
1076 * we set a very long timeout for the asynchronous allocation and if
1077 * the timeout is reached the cache is flagged as deadlocked. From
1078 * this point only new emergency objects will be allocated until the
1079 * asynchronous allocation completes and clears the deadlocked flag.
1081 if (test_bit(KMC_BIT_DEADLOCKED, &skc->skc_flags)) {
1082 rc = spl_emergency_alloc(skc, flags, obj);
1084 remaining = wait_event_timeout(skc->skc_waitq,
1085 spl_cache_grow_wait(skc), HZ / 10);
1088 spin_lock(&skc->skc_lock);
1089 if (test_bit(KMC_BIT_GROWING, &skc->skc_flags)) {
1090 set_bit(KMC_BIT_DEADLOCKED, &skc->skc_flags);
1091 skc->skc_obj_deadlock++;
1093 spin_unlock(&skc->skc_lock);
1103 * Refill a per-cpu magazine with objects from the slabs for this cache.
1104 * Ideally the magazine can be repopulated using existing objects which have
1105 * been released, however if we are unable to locate enough free objects new
1106 * slabs of objects will be created. On success NULL is returned, otherwise
1107 * the address of a single emergency object is returned for use by the caller.
1110 spl_cache_refill(spl_kmem_cache_t *skc, spl_kmem_magazine_t *skm, int flags)
1112 spl_kmem_slab_t *sks;
1113 int count = 0, rc, refill;
1116 ASSERT(skc->skc_magic == SKC_MAGIC);
1117 ASSERT(skm->skm_magic == SKM_MAGIC);
1119 refill = MIN(skm->skm_refill, skm->skm_size - skm->skm_avail);
1120 spin_lock(&skc->skc_lock);
1122 while (refill > 0) {
1123 /* No slabs available we may need to grow the cache */
1124 if (list_empty(&skc->skc_partial_list)) {
1125 spin_unlock(&skc->skc_lock);
1128 rc = spl_cache_grow(skc, flags, &obj);
1129 local_irq_disable();
1131 /* Emergency object for immediate use by caller */
1132 if (rc == 0 && obj != NULL)
1138 /* Rescheduled to different CPU skm is not local */
1139 if (skm != skc->skc_mag[smp_processor_id()])
1143 * Potentially rescheduled to the same CPU but
1144 * allocations may have occurred from this CPU while
1145 * we were sleeping so recalculate max refill.
1147 refill = MIN(refill, skm->skm_size - skm->skm_avail);
1149 spin_lock(&skc->skc_lock);
1153 /* Grab the next available slab */
1154 sks = list_entry((&skc->skc_partial_list)->next,
1155 spl_kmem_slab_t, sks_list);
1156 ASSERT(sks->sks_magic == SKS_MAGIC);
1157 ASSERT(sks->sks_ref < sks->sks_objs);
1158 ASSERT(!list_empty(&sks->sks_free_list));
1161 * Consume as many objects as needed to refill the requested
1162 * cache. We must also be careful not to overfill it.
1164 while (sks->sks_ref < sks->sks_objs && refill-- > 0 &&
1166 ASSERT(skm->skm_avail < skm->skm_size);
1167 ASSERT(count < skm->skm_size);
1168 skm->skm_objs[skm->skm_avail++] =
1169 spl_cache_obj(skc, sks);
1172 /* Move slab to skc_complete_list when full */
1173 if (sks->sks_ref == sks->sks_objs) {
1174 list_del(&sks->sks_list);
1175 list_add(&sks->sks_list, &skc->skc_complete_list);
1179 spin_unlock(&skc->skc_lock);
1185 * Release an object back to the slab from which it came.
1188 spl_cache_shrink(spl_kmem_cache_t *skc, void *obj)
1190 spl_kmem_slab_t *sks = NULL;
1191 spl_kmem_obj_t *sko = NULL;
1193 ASSERT(skc->skc_magic == SKC_MAGIC);
1195 sko = spl_sko_from_obj(skc, obj);
1196 ASSERT(sko->sko_magic == SKO_MAGIC);
1197 sks = sko->sko_slab;
1198 ASSERT(sks->sks_magic == SKS_MAGIC);
1199 ASSERT(sks->sks_cache == skc);
1200 list_add(&sko->sko_list, &sks->sks_free_list);
1202 sks->sks_age = jiffies;
1204 skc->skc_obj_alloc--;
1207 * Move slab to skc_partial_list when no longer full. Slabs
1208 * are added to the head to keep the partial list is quasi-full
1209 * sorted order. Fuller at the head, emptier at the tail.
1211 if (sks->sks_ref == (sks->sks_objs - 1)) {
1212 list_del(&sks->sks_list);
1213 list_add(&sks->sks_list, &skc->skc_partial_list);
1217 * Move empty slabs to the end of the partial list so
1218 * they can be easily found and freed during reclamation.
1220 if (sks->sks_ref == 0) {
1221 list_del(&sks->sks_list);
1222 list_add_tail(&sks->sks_list, &skc->skc_partial_list);
1223 skc->skc_slab_alloc--;
1228 * Allocate an object from the per-cpu magazine, or if the magazine
1229 * is empty directly allocate from a slab and repopulate the magazine.
1232 spl_kmem_cache_alloc(spl_kmem_cache_t *skc, int flags)
1234 spl_kmem_magazine_t *skm;
1237 ASSERT0(flags & ~KM_PUBLIC_MASK);
1238 ASSERT(skc->skc_magic == SKC_MAGIC);
1239 ASSERT(!test_bit(KMC_BIT_DESTROY, &skc->skc_flags));
1242 * Allocate directly from a Linux slab. All optimizations are left
1243 * to the underlying cache we only need to guarantee that KM_SLEEP
1244 * callers will never fail.
1246 if (skc->skc_flags & KMC_SLAB) {
1247 struct kmem_cache *slc = skc->skc_linux_cache;
1249 obj = kmem_cache_alloc(slc, kmem_flags_convert(flags));
1250 } while ((obj == NULL) && !(flags & KM_NOSLEEP));
1254 * Even though we leave everything up to the
1255 * underlying cache we still keep track of
1256 * how many objects we've allocated in it for
1257 * better debuggability.
1259 percpu_counter_inc(&skc->skc_linux_alloc);
1264 local_irq_disable();
1268 * Safe to update per-cpu structure without lock, but
1269 * in the restart case we must be careful to reacquire
1270 * the local magazine since this may have changed
1271 * when we need to grow the cache.
1273 skm = skc->skc_mag[smp_processor_id()];
1274 ASSERT(skm->skm_magic == SKM_MAGIC);
1276 if (likely(skm->skm_avail)) {
1277 /* Object available in CPU cache, use it */
1278 obj = skm->skm_objs[--skm->skm_avail];
1280 obj = spl_cache_refill(skc, skm, flags);
1281 if ((obj == NULL) && !(flags & KM_NOSLEEP))
1290 ASSERT(IS_P2ALIGNED(obj, skc->skc_obj_align));
1293 /* Pre-emptively migrate object to CPU L1 cache */
1295 if (obj && skc->skc_ctor)
1296 skc->skc_ctor(obj, skc->skc_private, flags);
1303 EXPORT_SYMBOL(spl_kmem_cache_alloc);
1306 * Free an object back to the local per-cpu magazine, there is no
1307 * guarantee that this is the same magazine the object was originally
1308 * allocated from. We may need to flush entire from the magazine
1309 * back to the slabs to make space.
1312 spl_kmem_cache_free(spl_kmem_cache_t *skc, void *obj)
1314 spl_kmem_magazine_t *skm;
1315 unsigned long flags;
1317 int do_emergency = 0;
1319 ASSERT(skc->skc_magic == SKC_MAGIC);
1320 ASSERT(!test_bit(KMC_BIT_DESTROY, &skc->skc_flags));
1323 * Run the destructor
1326 skc->skc_dtor(obj, skc->skc_private);
1329 * Free the object from the Linux underlying Linux slab.
1331 if (skc->skc_flags & KMC_SLAB) {
1332 kmem_cache_free(skc->skc_linux_cache, obj);
1333 percpu_counter_dec(&skc->skc_linux_alloc);
1338 * While a cache has outstanding emergency objects all freed objects
1339 * must be checked. However, since emergency objects will never use
1340 * a virtual address these objects can be safely excluded as an
1343 if (!is_vmalloc_addr(obj)) {
1344 spin_lock(&skc->skc_lock);
1345 do_emergency = (skc->skc_obj_emergency > 0);
1346 spin_unlock(&skc->skc_lock);
1348 if (do_emergency && (spl_emergency_free(skc, obj) == 0))
1352 local_irq_save(flags);
1355 * Safe to update per-cpu structure without lock, but
1356 * no remote memory allocation tracking is being performed
1357 * it is entirely possible to allocate an object from one
1358 * CPU cache and return it to another.
1360 skm = skc->skc_mag[smp_processor_id()];
1361 ASSERT(skm->skm_magic == SKM_MAGIC);
1364 * Per-CPU cache full, flush it to make space for this object,
1365 * this may result in an empty slab which can be reclaimed once
1366 * interrupts are re-enabled.
1368 if (unlikely(skm->skm_avail >= skm->skm_size)) {
1369 spl_cache_flush(skc, skm, skm->skm_refill);
1373 /* Available space in cache, use it */
1374 skm->skm_objs[skm->skm_avail++] = obj;
1376 local_irq_restore(flags);
1379 spl_slab_reclaim(skc);
1381 EXPORT_SYMBOL(spl_kmem_cache_free);
1384 * Depending on how many and which objects are released it may simply
1385 * repopulate the local magazine which will then need to age-out. Objects
1386 * which cannot fit in the magazine will be released back to their slabs
1387 * which will also need to age out before being released. This is all just
1388 * best effort and we do not want to thrash creating and destroying slabs.
1391 spl_kmem_cache_reap_now(spl_kmem_cache_t *skc)
1393 ASSERT(skc->skc_magic == SKC_MAGIC);
1394 ASSERT(!test_bit(KMC_BIT_DESTROY, &skc->skc_flags));
1396 if (skc->skc_flags & KMC_SLAB)
1399 atomic_inc(&skc->skc_ref);
1402 * Prevent concurrent cache reaping when contended.
1404 if (test_and_set_bit(KMC_BIT_REAPING, &skc->skc_flags))
1407 /* Reclaim from the magazine and free all now empty slabs. */
1408 unsigned long irq_flags;
1409 local_irq_save(irq_flags);
1410 spl_kmem_magazine_t *skm = skc->skc_mag[smp_processor_id()];
1411 spl_cache_flush(skc, skm, skm->skm_avail);
1412 local_irq_restore(irq_flags);
1414 spl_slab_reclaim(skc);
1415 clear_bit_unlock(KMC_BIT_REAPING, &skc->skc_flags);
1416 smp_mb__after_atomic();
1417 wake_up_bit(&skc->skc_flags, KMC_BIT_REAPING);
1419 atomic_dec(&skc->skc_ref);
1421 EXPORT_SYMBOL(spl_kmem_cache_reap_now);
1424 * This is stubbed out for code consistency with other platforms. There
1425 * is existing logic to prevent concurrent reaping so while this is ugly
1426 * it should do no harm.
1429 spl_kmem_cache_reap_active()
1433 EXPORT_SYMBOL(spl_kmem_cache_reap_active);
1436 * Reap all free slabs from all registered caches.
1441 spl_kmem_cache_t *skc = NULL;
1443 down_read(&spl_kmem_cache_sem);
1444 list_for_each_entry(skc, &spl_kmem_cache_list, skc_list) {
1445 spl_kmem_cache_reap_now(skc);
1447 up_read(&spl_kmem_cache_sem);
1449 EXPORT_SYMBOL(spl_kmem_reap);
1452 spl_kmem_cache_init(void)
1454 init_rwsem(&spl_kmem_cache_sem);
1455 INIT_LIST_HEAD(&spl_kmem_cache_list);
1456 spl_kmem_cache_taskq = taskq_create("spl_kmem_cache",
1457 spl_kmem_cache_kmem_threads, maxclsyspri,
1458 spl_kmem_cache_kmem_threads * 8, INT_MAX,
1459 TASKQ_PREPOPULATE | TASKQ_DYNAMIC);
1465 spl_kmem_cache_fini(void)
1467 taskq_destroy(spl_kmem_cache_taskq);