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Diffstat (limited to 'module/spl/spl-kmem-cache.c')
| -rw-r--r-- | module/spl/spl-kmem-cache.c | 1769 |
1 files changed, 1769 insertions, 0 deletions
diff --git a/module/spl/spl-kmem-cache.c b/module/spl/spl-kmem-cache.c new file mode 100644 index 000000000..5492c6a46 --- /dev/null +++ b/module/spl/spl-kmem-cache.c @@ -0,0 +1,1769 @@ +/* + * Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC. + * Copyright (C) 2007 The Regents of the University of California. + * Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER). + * Written by Brian Behlendorf <[email protected]>. + * UCRL-CODE-235197 + * + * This file is part of the SPL, Solaris Porting Layer. + * For details, see <http://zfsonlinux.org/>. + * + * The SPL is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License as published by the + * Free Software Foundation; either version 2 of the License, or (at your + * option) any later version. + * + * The SPL is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * for more details. + * + * You should have received a copy of the GNU General Public License along + * with the SPL. If not, see <http://www.gnu.org/licenses/>. + */ + +#include <sys/kmem.h> +#include <sys/kmem_cache.h> +#include <sys/shrinker.h> +#include <sys/taskq.h> +#include <sys/timer.h> +#include <sys/vmem.h> +#include <sys/wait.h> +#include <linux/slab.h> +#include <linux/swap.h> +#include <linux/prefetch.h> + +/* + * Within the scope of spl-kmem.c file the kmem_cache_* definitions + * are removed to allow access to the real Linux slab allocator. + */ +#undef kmem_cache_destroy +#undef kmem_cache_create +#undef kmem_cache_alloc +#undef kmem_cache_free + + +/* + * Linux 3.16 replaced smp_mb__{before,after}_{atomic,clear}_{dec,inc,bit}() + * with smp_mb__{before,after}_atomic() because they were redundant. This is + * only used inside our SLAB allocator, so we implement an internal wrapper + * here to give us smp_mb__{before,after}_atomic() on older kernels. + */ +#ifndef smp_mb__before_atomic +#define smp_mb__before_atomic(x) smp_mb__before_clear_bit(x) +#endif + +#ifndef smp_mb__after_atomic +#define smp_mb__after_atomic(x) smp_mb__after_clear_bit(x) +#endif + +/* + * Cache expiration was implemented because it was part of the default Solaris + * kmem_cache behavior. The idea is that per-cpu objects which haven't been + * accessed in several seconds should be returned to the cache. On the other + * hand Linux slabs never move objects back to the slabs unless there is + * memory pressure on the system. By default the Linux method is enabled + * because it has been shown to improve responsiveness on low memory systems. + * This policy may be changed by setting KMC_EXPIRE_AGE or KMC_EXPIRE_MEM. + */ +/* BEGIN CSTYLED */ +unsigned int spl_kmem_cache_expire = KMC_EXPIRE_MEM; +EXPORT_SYMBOL(spl_kmem_cache_expire); +module_param(spl_kmem_cache_expire, uint, 0644); +MODULE_PARM_DESC(spl_kmem_cache_expire, "By age (0x1) or low memory (0x2)"); + +/* + * Cache magazines are an optimization designed to minimize the cost of + * allocating memory. They do this by keeping a per-cpu cache of recently + * freed objects, which can then be reallocated without taking a lock. This + * can improve performance on highly contended caches. However, because + * objects in magazines will prevent otherwise empty slabs from being + * immediately released this may not be ideal for low memory machines. + * + * For this reason spl_kmem_cache_magazine_size can be used to set a maximum + * magazine size. When this value is set to 0 the magazine size will be + * automatically determined based on the object size. Otherwise magazines + * will be limited to 2-256 objects per magazine (i.e per cpu). Magazines + * may never be entirely disabled in this implementation. + */ +unsigned int spl_kmem_cache_magazine_size = 0; +module_param(spl_kmem_cache_magazine_size, uint, 0444); +MODULE_PARM_DESC(spl_kmem_cache_magazine_size, + "Default magazine size (2-256), set automatically (0)"); + +/* + * The default behavior is to report the number of objects remaining in the + * cache. This allows the Linux VM to repeatedly reclaim objects from the + * cache when memory is low satisfy other memory allocations. Alternately, + * setting this value to KMC_RECLAIM_ONCE limits how aggressively the cache + * is reclaimed. This may increase the likelihood of out of memory events. + */ +unsigned int spl_kmem_cache_reclaim = 0 /* KMC_RECLAIM_ONCE */; +module_param(spl_kmem_cache_reclaim, uint, 0644); +MODULE_PARM_DESC(spl_kmem_cache_reclaim, "Single reclaim pass (0x1)"); + +unsigned int spl_kmem_cache_obj_per_slab = SPL_KMEM_CACHE_OBJ_PER_SLAB; +module_param(spl_kmem_cache_obj_per_slab, uint, 0644); +MODULE_PARM_DESC(spl_kmem_cache_obj_per_slab, "Number of objects per slab"); + +unsigned int spl_kmem_cache_obj_per_slab_min = SPL_KMEM_CACHE_OBJ_PER_SLAB_MIN; +module_param(spl_kmem_cache_obj_per_slab_min, uint, 0644); +MODULE_PARM_DESC(spl_kmem_cache_obj_per_slab_min, + "Minimal number of objects per slab"); + +unsigned int spl_kmem_cache_max_size = SPL_KMEM_CACHE_MAX_SIZE; +module_param(spl_kmem_cache_max_size, uint, 0644); +MODULE_PARM_DESC(spl_kmem_cache_max_size, "Maximum size of slab in MB"); + +/* + * For small objects the Linux slab allocator should be used to make the most + * efficient use of the memory. However, large objects are not supported by + * the Linux slab and therefore the SPL implementation is preferred. A cutoff + * of 16K was determined to be optimal for architectures using 4K pages. + */ +#if PAGE_SIZE == 4096 +unsigned int spl_kmem_cache_slab_limit = 16384; +#else +unsigned int spl_kmem_cache_slab_limit = 0; +#endif +module_param(spl_kmem_cache_slab_limit, uint, 0644); +MODULE_PARM_DESC(spl_kmem_cache_slab_limit, + "Objects less than N bytes use the Linux slab"); + +/* + * This value defaults to a threshold designed to avoid allocations which + * have been deemed costly by the kernel. + */ +unsigned int spl_kmem_cache_kmem_limit = + ((1 << (PAGE_ALLOC_COSTLY_ORDER - 1)) * PAGE_SIZE) / + SPL_KMEM_CACHE_OBJ_PER_SLAB; +module_param(spl_kmem_cache_kmem_limit, uint, 0644); +MODULE_PARM_DESC(spl_kmem_cache_kmem_limit, + "Objects less than N bytes use the kmalloc"); + +/* + * The number of threads available to allocate new slabs for caches. This + * should not need to be tuned but it is available for performance analysis. + */ +unsigned int spl_kmem_cache_kmem_threads = 4; +module_param(spl_kmem_cache_kmem_threads, uint, 0444); +MODULE_PARM_DESC(spl_kmem_cache_kmem_threads, + "Number of spl_kmem_cache threads"); +/* END CSTYLED */ + +/* + * Slab allocation interfaces + * + * While the Linux slab implementation was inspired by the Solaris + * implementation I cannot use it to emulate the Solaris APIs. I + * require two features which are not provided by the Linux slab. + * + * 1) Constructors AND destructors. Recent versions of the Linux + * kernel have removed support for destructors. This is a deal + * breaker for the SPL which contains particularly expensive + * initializers for mutex's, condition variables, etc. We also + * require a minimal level of cleanup for these data types unlike + * many Linux data types which do need to be explicitly destroyed. + * + * 2) Virtual address space backed slab. Callers of the Solaris slab + * expect it to work well for both small are very large allocations. + * Because of memory fragmentation the Linux slab which is backed + * by kmalloc'ed memory performs very badly when confronted with + * large numbers of large allocations. Basing the slab on the + * virtual address space removes the need for contiguous pages + * and greatly improve performance for large allocations. + * + * For these reasons, the SPL has its own slab implementation with + * the needed features. It is not as highly optimized as either the + * Solaris or Linux slabs, but it should get me most of what is + * needed until it can be optimized or obsoleted by another approach. + * + * One serious concern I do have about this method is the relatively + * small virtual address space on 32bit arches. This will seriously + * constrain the size of the slab caches and their performance. + */ + +struct list_head spl_kmem_cache_list; /* List of caches */ +struct rw_semaphore spl_kmem_cache_sem; /* Cache list lock */ +taskq_t *spl_kmem_cache_taskq; /* Task queue for ageing / reclaim */ + +static void spl_cache_shrink(spl_kmem_cache_t *skc, void *obj); + +SPL_SHRINKER_CALLBACK_FWD_DECLARE(spl_kmem_cache_generic_shrinker); +SPL_SHRINKER_DECLARE(spl_kmem_cache_shrinker, + spl_kmem_cache_generic_shrinker, KMC_DEFAULT_SEEKS); + +static void * +kv_alloc(spl_kmem_cache_t *skc, int size, int flags) +{ + gfp_t lflags = kmem_flags_convert(flags); + void *ptr; + + if (skc->skc_flags & KMC_KMEM) { + ASSERT(ISP2(size)); + ptr = (void *)__get_free_pages(lflags, get_order(size)); + } else { + ptr = __vmalloc(size, lflags | __GFP_HIGHMEM, PAGE_KERNEL); + } + + /* Resulting allocated memory will be page aligned */ + ASSERT(IS_P2ALIGNED(ptr, PAGE_SIZE)); + + return (ptr); +} + +static void +kv_free(spl_kmem_cache_t *skc, void *ptr, int size) +{ + ASSERT(IS_P2ALIGNED(ptr, PAGE_SIZE)); + + /* + * The Linux direct reclaim path uses this out of band value to + * determine if forward progress is being made. Normally this is + * incremented by kmem_freepages() which is part of the various + * Linux slab implementations. However, since we are using none + * of that infrastructure we are responsible for incrementing it. + */ + if (current->reclaim_state) + current->reclaim_state->reclaimed_slab += size >> PAGE_SHIFT; + + if (skc->skc_flags & KMC_KMEM) { + ASSERT(ISP2(size)); + free_pages((unsigned long)ptr, get_order(size)); + } else { + vfree(ptr); + } +} + +/* + * Required space for each aligned sks. + */ +static inline uint32_t +spl_sks_size(spl_kmem_cache_t *skc) +{ + return (P2ROUNDUP_TYPED(sizeof (spl_kmem_slab_t), + skc->skc_obj_align, uint32_t)); +} + +/* + * Required space for each aligned object. + */ +static inline uint32_t +spl_obj_size(spl_kmem_cache_t *skc) +{ + uint32_t align = skc->skc_obj_align; + + return (P2ROUNDUP_TYPED(skc->skc_obj_size, align, uint32_t) + + P2ROUNDUP_TYPED(sizeof (spl_kmem_obj_t), align, uint32_t)); +} + +/* + * Lookup the spl_kmem_object_t for an object given that object. + */ +static inline spl_kmem_obj_t * +spl_sko_from_obj(spl_kmem_cache_t *skc, void *obj) +{ + return (obj + P2ROUNDUP_TYPED(skc->skc_obj_size, + skc->skc_obj_align, uint32_t)); +} + +/* + * Required space for each offslab object taking in to account alignment + * restrictions and the power-of-two requirement of kv_alloc(). + */ +static inline uint32_t +spl_offslab_size(spl_kmem_cache_t *skc) +{ + return (1UL << (fls64(spl_obj_size(skc)) + 1)); +} + +/* + * It's important that we pack the spl_kmem_obj_t structure and the + * actual objects in to one large address space to minimize the number + * of calls to the allocator. It is far better to do a few large + * allocations and then subdivide it ourselves. Now which allocator + * we use requires balancing a few trade offs. + * + * For small objects we use kmem_alloc() because as long as you are + * only requesting a small number of pages (ideally just one) its cheap. + * However, when you start requesting multiple pages with kmem_alloc() + * it gets increasingly expensive since it requires contiguous pages. + * For this reason we shift to vmem_alloc() for slabs of large objects + * which removes the need for contiguous pages. We do not use + * vmem_alloc() in all cases because there is significant locking + * overhead in __get_vm_area_node(). This function takes a single + * global lock when acquiring an available virtual address range which + * serializes all vmem_alloc()'s for all slab caches. Using slightly + * different allocation functions for small and large objects should + * give us the best of both worlds. + * + * KMC_ONSLAB KMC_OFFSLAB + * + * +------------------------+ +-----------------+ + * | spl_kmem_slab_t --+-+ | | spl_kmem_slab_t |---+-+ + * | skc_obj_size <-+ | | +-----------------+ | | + * | spl_kmem_obj_t | | | | + * | skc_obj_size <---+ | +-----------------+ | | + * | spl_kmem_obj_t | | | skc_obj_size | <-+ | + * | ... v | | spl_kmem_obj_t | | + * +------------------------+ +-----------------+ v + */ +static spl_kmem_slab_t * +spl_slab_alloc(spl_kmem_cache_t *skc, int flags) +{ + spl_kmem_slab_t *sks; + spl_kmem_obj_t *sko, *n; + void *base, *obj; + uint32_t obj_size, offslab_size = 0; + int i, rc = 0; + + base = kv_alloc(skc, skc->skc_slab_size, flags); + if (base == NULL) + return (NULL); + + sks = (spl_kmem_slab_t *)base; + sks->sks_magic = SKS_MAGIC; + sks->sks_objs = skc->skc_slab_objs; + sks->sks_age = jiffies; + sks->sks_cache = skc; + INIT_LIST_HEAD(&sks->sks_list); + INIT_LIST_HEAD(&sks->sks_free_list); + sks->sks_ref = 0; + obj_size = spl_obj_size(skc); + + if (skc->skc_flags & KMC_OFFSLAB) + offslab_size = spl_offslab_size(skc); + + for (i = 0; i < sks->sks_objs; i++) { + if (skc->skc_flags & KMC_OFFSLAB) { + obj = kv_alloc(skc, offslab_size, flags); + if (!obj) { + rc = -ENOMEM; + goto out; + } + } else { + obj = base + spl_sks_size(skc) + (i * obj_size); + } + + ASSERT(IS_P2ALIGNED(obj, skc->skc_obj_align)); + sko = spl_sko_from_obj(skc, obj); + sko->sko_addr = obj; + sko->sko_magic = SKO_MAGIC; + sko->sko_slab = sks; + INIT_LIST_HEAD(&sko->sko_list); + list_add_tail(&sko->sko_list, &sks->sks_free_list); + } + +out: + if (rc) { + if (skc->skc_flags & KMC_OFFSLAB) + list_for_each_entry_safe(sko, + n, &sks->sks_free_list, sko_list) { + kv_free(skc, sko->sko_addr, offslab_size); + } + + kv_free(skc, base, skc->skc_slab_size); + sks = NULL; + } + + return (sks); +} + +/* + * Remove a slab from complete or partial list, it must be called with + * the 'skc->skc_lock' held but the actual free must be performed + * outside the lock to prevent deadlocking on vmem addresses. + */ +static void +spl_slab_free(spl_kmem_slab_t *sks, + struct list_head *sks_list, struct list_head *sko_list) +{ + spl_kmem_cache_t *skc; + + ASSERT(sks->sks_magic == SKS_MAGIC); + ASSERT(sks->sks_ref == 0); + + skc = sks->sks_cache; + ASSERT(skc->skc_magic == SKC_MAGIC); + + /* + * Update slab/objects counters in the cache, then remove the + * slab from the skc->skc_partial_list. Finally add the slab + * and all its objects in to the private work lists where the + * destructors will be called and the memory freed to the system. + */ + skc->skc_obj_total -= sks->sks_objs; + skc->skc_slab_total--; + list_del(&sks->sks_list); + list_add(&sks->sks_list, sks_list); + list_splice_init(&sks->sks_free_list, sko_list); +} + +/* + * Reclaim empty slabs at the end of the partial list. + */ +static void +spl_slab_reclaim(spl_kmem_cache_t *skc) +{ + spl_kmem_slab_t *sks, *m; + spl_kmem_obj_t *sko, *n; + LIST_HEAD(sks_list); + LIST_HEAD(sko_list); + uint32_t size = 0; + + /* + * Empty slabs and objects must be moved to a private list so they + * can be safely freed outside the spin lock. All empty slabs are + * at the end of skc->skc_partial_list, therefore once a non-empty + * slab is found we can stop scanning. + */ + spin_lock(&skc->skc_lock); + list_for_each_entry_safe_reverse(sks, m, + &skc->skc_partial_list, sks_list) { + + if (sks->sks_ref > 0) + break; + + spl_slab_free(sks, &sks_list, &sko_list); + } + spin_unlock(&skc->skc_lock); + + /* + * The following two loops ensure all the object destructors are + * run, any offslab objects are freed, and the slabs themselves + * are freed. This is all done outside the skc->skc_lock since + * this allows the destructor to sleep, and allows us to perform + * a conditional reschedule when a freeing a large number of + * objects and slabs back to the system. + */ + if (skc->skc_flags & KMC_OFFSLAB) + size = spl_offslab_size(skc); + + list_for_each_entry_safe(sko, n, &sko_list, sko_list) { + ASSERT(sko->sko_magic == SKO_MAGIC); + + if (skc->skc_flags & KMC_OFFSLAB) + kv_free(skc, sko->sko_addr, size); + } + + list_for_each_entry_safe(sks, m, &sks_list, sks_list) { + ASSERT(sks->sks_magic == SKS_MAGIC); + kv_free(skc, sks, skc->skc_slab_size); + } +} + +static spl_kmem_emergency_t * +spl_emergency_search(struct rb_root *root, void *obj) +{ + struct rb_node *node = root->rb_node; + spl_kmem_emergency_t *ske; + unsigned long address = (unsigned long)obj; + + while (node) { + ske = container_of(node, spl_kmem_emergency_t, ske_node); + + if (address < ske->ske_obj) + node = node->rb_left; + else if (address > ske->ske_obj) + node = node->rb_right; + else + return (ske); + } + + return (NULL); +} + +static int +spl_emergency_insert(struct rb_root *root, spl_kmem_emergency_t *ske) +{ + struct rb_node **new = &(root->rb_node), *parent = NULL; + spl_kmem_emergency_t *ske_tmp; + unsigned long address = ske->ske_obj; + + while (*new) { + ske_tmp = container_of(*new, spl_kmem_emergency_t, ske_node); + + parent = *new; + if (address < ske_tmp->ske_obj) + new = &((*new)->rb_left); + else if (address > ske_tmp->ske_obj) + new = &((*new)->rb_right); + else + return (0); + } + + rb_link_node(&ske->ske_node, parent, new); + rb_insert_color(&ske->ske_node, root); + + return (1); +} + +/* + * Allocate a single emergency object and track it in a red black tree. + */ +static int +spl_emergency_alloc(spl_kmem_cache_t *skc, int flags, void **obj) +{ + gfp_t lflags = kmem_flags_convert(flags); + spl_kmem_emergency_t *ske; + int order = get_order(skc->skc_obj_size); + int empty; + + /* Last chance use a partial slab if one now exists */ + spin_lock(&skc->skc_lock); + empty = list_empty(&skc->skc_partial_list); + spin_unlock(&skc->skc_lock); + if (!empty) + return (-EEXIST); + + ske = kmalloc(sizeof (*ske), lflags); + if (ske == NULL) + return (-ENOMEM); + + ske->ske_obj = __get_free_pages(lflags, order); + if (ske->ske_obj == 0) { + kfree(ske); + return (-ENOMEM); + } + + spin_lock(&skc->skc_lock); + empty = spl_emergency_insert(&skc->skc_emergency_tree, ske); + if (likely(empty)) { + skc->skc_obj_total++; + skc->skc_obj_emergency++; + if (skc->skc_obj_emergency > skc->skc_obj_emergency_max) + skc->skc_obj_emergency_max = skc->skc_obj_emergency; + } + spin_unlock(&skc->skc_lock); + + if (unlikely(!empty)) { + free_pages(ske->ske_obj, order); + kfree(ske); + return (-EINVAL); + } + + *obj = (void *)ske->ske_obj; + + return (0); +} + +/* + * Locate the passed object in the red black tree and free it. + */ +static int +spl_emergency_free(spl_kmem_cache_t *skc, void *obj) +{ + spl_kmem_emergency_t *ske; + int order = get_order(skc->skc_obj_size); + + spin_lock(&skc->skc_lock); + ske = spl_emergency_search(&skc->skc_emergency_tree, obj); + if (ske) { + rb_erase(&ske->ske_node, &skc->skc_emergency_tree); + skc->skc_obj_emergency--; + skc->skc_obj_total--; + } + spin_unlock(&skc->skc_lock); + + if (ske == NULL) + return (-ENOENT); + + free_pages(ske->ske_obj, order); + kfree(ske); + + return (0); +} + +/* + * Release objects from the per-cpu magazine back to their slab. The flush + * argument contains the max number of entries to remove from the magazine. + */ +static void +__spl_cache_flush(spl_kmem_cache_t *skc, spl_kmem_magazine_t *skm, int flush) +{ + int i, count = MIN(flush, skm->skm_avail); + + ASSERT(skc->skc_magic == SKC_MAGIC); + ASSERT(skm->skm_magic == SKM_MAGIC); + + for (i = 0; i < count; i++) + spl_cache_shrink(skc, skm->skm_objs[i]); + + skm->skm_avail -= count; + memmove(skm->skm_objs, &(skm->skm_objs[count]), + sizeof (void *) * skm->skm_avail); +} + +static void +spl_cache_flush(spl_kmem_cache_t *skc, spl_kmem_magazine_t *skm, int flush) +{ + spin_lock(&skc->skc_lock); + __spl_cache_flush(skc, skm, flush); + spin_unlock(&skc->skc_lock); +} + +static void +spl_magazine_age(void *data) +{ + spl_kmem_cache_t *skc = (spl_kmem_cache_t *)data; + spl_kmem_magazine_t *skm = skc->skc_mag[smp_processor_id()]; + + ASSERT(skm->skm_magic == SKM_MAGIC); + ASSERT(skm->skm_cpu == smp_processor_id()); + ASSERT(irqs_disabled()); + + /* There are no available objects or they are too young to age out */ + if ((skm->skm_avail == 0) || + time_before(jiffies, skm->skm_age + skc->skc_delay * HZ)) + return; + + /* + * Because we're executing in interrupt context we may have + * interrupted the holder of this lock. To avoid a potential + * deadlock return if the lock is contended. + */ + if (!spin_trylock(&skc->skc_lock)) + return; + + __spl_cache_flush(skc, skm, skm->skm_refill); + spin_unlock(&skc->skc_lock); +} + +/* + * Called regularly to keep a downward pressure on the cache. + * + * Objects older than skc->skc_delay seconds in the per-cpu magazines will + * be returned to the caches. This is done to prevent idle magazines from + * holding memory which could be better used elsewhere. The delay is + * present to prevent thrashing the magazine. + * + * The newly released objects may result in empty partial slabs. Those + * slabs should be released to the system. Otherwise moving the objects + * out of the magazines is just wasted work. + */ +static void +spl_cache_age(void *data) +{ + spl_kmem_cache_t *skc = (spl_kmem_cache_t *)data; + taskqid_t id = 0; + + ASSERT(skc->skc_magic == SKC_MAGIC); + + /* Dynamically disabled at run time */ + if (!(spl_kmem_cache_expire & KMC_EXPIRE_AGE)) + return; + + atomic_inc(&skc->skc_ref); + + if (!(skc->skc_flags & KMC_NOMAGAZINE)) + on_each_cpu(spl_magazine_age, skc, 1); + + spl_slab_reclaim(skc); + + while (!test_bit(KMC_BIT_DESTROY, &skc->skc_flags) && !id) { + id = taskq_dispatch_delay( + spl_kmem_cache_taskq, spl_cache_age, skc, TQ_SLEEP, + ddi_get_lbolt() + skc->skc_delay / 3 * HZ); + + /* Destroy issued after dispatch immediately cancel it */ + if (test_bit(KMC_BIT_DESTROY, &skc->skc_flags) && id) + taskq_cancel_id(spl_kmem_cache_taskq, id); + } + + spin_lock(&skc->skc_lock); + skc->skc_taskqid = id; + spin_unlock(&skc->skc_lock); + + atomic_dec(&skc->skc_ref); +} + +/* + * Size a slab based on the size of each aligned object plus spl_kmem_obj_t. + * When on-slab we want to target spl_kmem_cache_obj_per_slab. However, + * for very small objects we may end up with more than this so as not + * to waste space in the minimal allocation of a single page. Also for + * very large objects we may use as few as spl_kmem_cache_obj_per_slab_min, + * lower than this and we will fail. + */ +static int +spl_slab_size(spl_kmem_cache_t *skc, uint32_t *objs, uint32_t *size) +{ + uint32_t sks_size, obj_size, max_size, tgt_size, tgt_objs; + + if (skc->skc_flags & KMC_OFFSLAB) { + tgt_objs = spl_kmem_cache_obj_per_slab; + tgt_size = P2ROUNDUP(sizeof (spl_kmem_slab_t), PAGE_SIZE); + + if ((skc->skc_flags & KMC_KMEM) && + (spl_obj_size(skc) > (SPL_MAX_ORDER_NR_PAGES * PAGE_SIZE))) + return (-ENOSPC); + } else { + sks_size = spl_sks_size(skc); + obj_size = spl_obj_size(skc); + max_size = (spl_kmem_cache_max_size * 1024 * 1024); + tgt_size = (spl_kmem_cache_obj_per_slab * obj_size + sks_size); + + /* + * KMC_KMEM slabs are allocated by __get_free_pages() which + * rounds up to the nearest order. Knowing this the size + * should be rounded up to the next power of two with a hard + * maximum defined by the maximum allowed allocation order. + */ + if (skc->skc_flags & KMC_KMEM) { + max_size = SPL_MAX_ORDER_NR_PAGES * PAGE_SIZE; + tgt_size = MIN(max_size, + PAGE_SIZE * (1 << MAX(get_order(tgt_size) - 1, 1))); + } + + if (tgt_size <= max_size) { + tgt_objs = (tgt_size - sks_size) / obj_size; + } else { + tgt_objs = (max_size - sks_size) / obj_size; + tgt_size = (tgt_objs * obj_size) + sks_size; + } + } + + if (tgt_objs == 0) + return (-ENOSPC); + + *objs = tgt_objs; + *size = tgt_size; + + return (0); +} + +/* + * Make a guess at reasonable per-cpu magazine size based on the size of + * each object and the cost of caching N of them in each magazine. Long + * term this should really adapt based on an observed usage heuristic. + */ +static int +spl_magazine_size(spl_kmem_cache_t *skc) +{ + uint32_t obj_size = spl_obj_size(skc); + int size; + + if (spl_kmem_cache_magazine_size > 0) + return (MAX(MIN(spl_kmem_cache_magazine_size, 256), 2)); + + /* Per-magazine sizes below assume a 4Kib page size */ + if (obj_size > (PAGE_SIZE * 256)) + size = 4; /* Minimum 4Mib per-magazine */ + else if (obj_size > (PAGE_SIZE * 32)) + size = 16; /* Minimum 2Mib per-magazine */ + else if (obj_size > (PAGE_SIZE)) + size = 64; /* Minimum 256Kib per-magazine */ + else if (obj_size > (PAGE_SIZE / 4)) + size = 128; /* Minimum 128Kib per-magazine */ + else + size = 256; + + return (size); +} + +/* + * Allocate a per-cpu magazine to associate with a specific core. + */ +static spl_kmem_magazine_t * +spl_magazine_alloc(spl_kmem_cache_t *skc, int cpu) +{ + spl_kmem_magazine_t *skm; + int size = sizeof (spl_kmem_magazine_t) + + sizeof (void *) * skc->skc_mag_size; + + skm = kmalloc_node(size, GFP_KERNEL, cpu_to_node(cpu)); + if (skm) { + skm->skm_magic = SKM_MAGIC; + skm->skm_avail = 0; + skm->skm_size = skc->skc_mag_size; + skm->skm_refill = skc->skc_mag_refill; + skm->skm_cache = skc; + skm->skm_age = jiffies; + skm->skm_cpu = cpu; + } + + return (skm); +} + +/* + * Free a per-cpu magazine associated with a specific core. + */ +static void +spl_magazine_free(spl_kmem_magazine_t *skm) +{ + ASSERT(skm->skm_magic == SKM_MAGIC); + ASSERT(skm->skm_avail == 0); + kfree(skm); +} + +/* + * Create all pre-cpu magazines of reasonable sizes. + */ +static int +spl_magazine_create(spl_kmem_cache_t *skc) +{ + int i; + + if (skc->skc_flags & KMC_NOMAGAZINE) + return (0); + + skc->skc_mag = kzalloc(sizeof (spl_kmem_magazine_t *) * + num_possible_cpus(), kmem_flags_convert(KM_SLEEP)); + skc->skc_mag_size = spl_magazine_size(skc); + skc->skc_mag_refill = (skc->skc_mag_size + 1) / 2; + + for_each_possible_cpu(i) { + skc->skc_mag[i] = spl_magazine_alloc(skc, i); + if (!skc->skc_mag[i]) { + for (i--; i >= 0; i--) + spl_magazine_free(skc->skc_mag[i]); + + kfree(skc->skc_mag); + return (-ENOMEM); + } + } + + return (0); +} + +/* + * Destroy all pre-cpu magazines. + */ +static void +spl_magazine_destroy(spl_kmem_cache_t *skc) +{ + spl_kmem_magazine_t *skm; + int i; + + if (skc->skc_flags & KMC_NOMAGAZINE) + return; + + for_each_possible_cpu(i) { + skm = skc->skc_mag[i]; + spl_cache_flush(skc, skm, skm->skm_avail); + spl_magazine_free(skm); + } + + kfree(skc->skc_mag); +} + +/* + * Create a object cache based on the following arguments: + * name cache name + * size cache object size + * align cache object alignment + * ctor cache object constructor + * dtor cache object destructor + * reclaim cache object reclaim + * priv cache private data for ctor/dtor/reclaim + * vmp unused must be NULL + * flags + * KMC_NOTOUCH Disable cache object aging (unsupported) + * KMC_NODEBUG Disable debugging (unsupported) + * KMC_NOHASH Disable hashing (unsupported) + * KMC_QCACHE Disable qcache (unsupported) + * KMC_NOMAGAZINE Enabled for kmem/vmem, Disabled for Linux slab + * KMC_KMEM Force kmem backed cache + * KMC_VMEM Force vmem backed cache + * KMC_SLAB Force Linux slab backed cache + * KMC_OFFSLAB Locate objects off the slab + */ +spl_kmem_cache_t * +spl_kmem_cache_create(char *name, size_t size, size_t align, + spl_kmem_ctor_t ctor, spl_kmem_dtor_t dtor, spl_kmem_reclaim_t reclaim, + void *priv, void *vmp, int flags) +{ + gfp_t lflags = kmem_flags_convert(KM_SLEEP); + spl_kmem_cache_t *skc; + int rc; + + /* + * Unsupported flags + */ + ASSERT0(flags & KMC_NOMAGAZINE); + ASSERT0(flags & KMC_NOHASH); + ASSERT0(flags & KMC_QCACHE); + ASSERT(vmp == NULL); + + might_sleep(); + + skc = kzalloc(sizeof (*skc), lflags); + if (skc == NULL) + return (NULL); + + skc->skc_magic = SKC_MAGIC; + skc->skc_name_size = strlen(name) + 1; + skc->skc_name = (char *)kmalloc(skc->skc_name_size, lflags); + if (skc->skc_name == NULL) { + kfree(skc); + return (NULL); + } + strncpy(skc->skc_name, name, skc->skc_name_size); + + skc->skc_ctor = ctor; + skc->skc_dtor = dtor; + skc->skc_reclaim = reclaim; + skc->skc_private = priv; + skc->skc_vmp = vmp; + skc->skc_linux_cache = NULL; + skc->skc_flags = flags; + skc->skc_obj_size = size; + skc->skc_obj_align = SPL_KMEM_CACHE_ALIGN; + skc->skc_delay = SPL_KMEM_CACHE_DELAY; + skc->skc_reap = SPL_KMEM_CACHE_REAP; + atomic_set(&skc->skc_ref, 0); + + INIT_LIST_HEAD(&skc->skc_list); + INIT_LIST_HEAD(&skc->skc_complete_list); + INIT_LIST_HEAD(&skc->skc_partial_list); + skc->skc_emergency_tree = RB_ROOT; + spin_lock_init(&skc->skc_lock); + init_waitqueue_head(&skc->skc_waitq); + skc->skc_slab_fail = 0; + skc->skc_slab_create = 0; + skc->skc_slab_destroy = 0; + skc->skc_slab_total = 0; + skc->skc_slab_alloc = 0; + skc->skc_slab_max = 0; + skc->skc_obj_total = 0; + skc->skc_obj_alloc = 0; + skc->skc_obj_max = 0; + skc->skc_obj_deadlock = 0; + skc->skc_obj_emergency = 0; + skc->skc_obj_emergency_max = 0; + + /* + * Verify the requested alignment restriction is sane. + */ + if (align) { + VERIFY(ISP2(align)); + VERIFY3U(align, >=, SPL_KMEM_CACHE_ALIGN); + VERIFY3U(align, <=, PAGE_SIZE); + skc->skc_obj_align = align; + } + + /* + * When no specific type of slab is requested (kmem, vmem, or + * linuxslab) then select a cache type based on the object size + * and default tunables. + */ + if (!(skc->skc_flags & (KMC_KMEM | KMC_VMEM | KMC_SLAB))) { + + /* + * Objects smaller than spl_kmem_cache_slab_limit can + * use the Linux slab for better space-efficiency. By + * default this functionality is disabled until its + * performance characteristics are fully understood. + */ + if (spl_kmem_cache_slab_limit && + size <= (size_t)spl_kmem_cache_slab_limit) + skc->skc_flags |= KMC_SLAB; + + /* + * Small objects, less than spl_kmem_cache_kmem_limit per + * object should use kmem because their slabs are small. + */ + else if (spl_obj_size(skc) <= spl_kmem_cache_kmem_limit) + skc->skc_flags |= KMC_KMEM; + + /* + * All other objects are considered large and are placed + * on vmem backed slabs. + */ + else + skc->skc_flags |= KMC_VMEM; + } + + /* + * Given the type of slab allocate the required resources. + */ + if (skc->skc_flags & (KMC_KMEM | KMC_VMEM)) { + rc = spl_slab_size(skc, + &skc->skc_slab_objs, &skc->skc_slab_size); + if (rc) + goto out; + + rc = spl_magazine_create(skc); + if (rc) + goto out; + } else { + unsigned long slabflags = 0; + + if (size > (SPL_MAX_KMEM_ORDER_NR_PAGES * PAGE_SIZE)) { + rc = EINVAL; + goto out; + } + +#if defined(SLAB_USERCOPY) + /* + * Required for PAX-enabled kernels if the slab is to be + * used for coping between user and kernel space. + */ + slabflags |= SLAB_USERCOPY; +#endif + +#if defined(HAVE_KMEM_CACHE_CREATE_USERCOPY) + /* + * Newer grsec patchset uses kmem_cache_create_usercopy() + * instead of SLAB_USERCOPY flag + */ + skc->skc_linux_cache = kmem_cache_create_usercopy( + skc->skc_name, size, align, slabflags, 0, size, NULL); +#else + skc->skc_linux_cache = kmem_cache_create( + skc->skc_name, size, align, slabflags, NULL); +#endif + if (skc->skc_linux_cache == NULL) { + rc = ENOMEM; + goto out; + } + +#if defined(HAVE_KMEM_CACHE_ALLOCFLAGS) + skc->skc_linux_cache->allocflags |= __GFP_COMP; +#elif defined(HAVE_KMEM_CACHE_GFPFLAGS) + skc->skc_linux_cache->gfpflags |= __GFP_COMP; +#endif + skc->skc_flags |= KMC_NOMAGAZINE; + } + + if (spl_kmem_cache_expire & KMC_EXPIRE_AGE) + skc->skc_taskqid = taskq_dispatch_delay(spl_kmem_cache_taskq, + spl_cache_age, skc, TQ_SLEEP, + ddi_get_lbolt() + skc->skc_delay / 3 * HZ); + + down_write(&spl_kmem_cache_sem); + list_add_tail(&skc->skc_list, &spl_kmem_cache_list); + up_write(&spl_kmem_cache_sem); + + return (skc); +out: + kfree(skc->skc_name); + kfree(skc); + return (NULL); +} +EXPORT_SYMBOL(spl_kmem_cache_create); + +/* + * Register a move callback for cache defragmentation. + * XXX: Unimplemented but harmless to stub out for now. + */ +void +spl_kmem_cache_set_move(spl_kmem_cache_t *skc, + kmem_cbrc_t (move)(void *, void *, size_t, void *)) +{ + ASSERT(move != NULL); +} +EXPORT_SYMBOL(spl_kmem_cache_set_move); + +/* + * Destroy a cache and all objects associated with the cache. + */ +void +spl_kmem_cache_destroy(spl_kmem_cache_t *skc) +{ + DECLARE_WAIT_QUEUE_HEAD(wq); + taskqid_t id; + + ASSERT(skc->skc_magic == SKC_MAGIC); + ASSERT(skc->skc_flags & (KMC_KMEM | KMC_VMEM | KMC_SLAB)); + + down_write(&spl_kmem_cache_sem); + list_del_init(&skc->skc_list); + up_write(&spl_kmem_cache_sem); + + /* Cancel any and wait for any pending delayed tasks */ + VERIFY(!test_and_set_bit(KMC_BIT_DESTROY, &skc->skc_flags)); + + spin_lock(&skc->skc_lock); + id = skc->skc_taskqid; + spin_unlock(&skc->skc_lock); + + taskq_cancel_id(spl_kmem_cache_taskq, id); + + /* + * Wait until all current callers complete, this is mainly + * to catch the case where a low memory situation triggers a + * cache reaping action which races with this destroy. + */ + wait_event(wq, atomic_read(&skc->skc_ref) == 0); + + if (skc->skc_flags & (KMC_KMEM | KMC_VMEM)) { + spl_magazine_destroy(skc); + spl_slab_reclaim(skc); + } else { + ASSERT(skc->skc_flags & KMC_SLAB); + kmem_cache_destroy(skc->skc_linux_cache); + } + + spin_lock(&skc->skc_lock); + + /* + * Validate there are no objects in use and free all the + * spl_kmem_slab_t, spl_kmem_obj_t, and object buffers. + */ + ASSERT3U(skc->skc_slab_alloc, ==, 0); + ASSERT3U(skc->skc_obj_alloc, ==, 0); + ASSERT3U(skc->skc_slab_total, ==, 0); + ASSERT3U(skc->skc_obj_total, ==, 0); + ASSERT3U(skc->skc_obj_emergency, ==, 0); + ASSERT(list_empty(&skc->skc_complete_list)); + + spin_unlock(&skc->skc_lock); + + kfree(skc->skc_name); + kfree(skc); +} +EXPORT_SYMBOL(spl_kmem_cache_destroy); + +/* + * Allocate an object from a slab attached to the cache. This is used to + * repopulate the per-cpu magazine caches in batches when they run low. + */ +static void * +spl_cache_obj(spl_kmem_cache_t *skc, spl_kmem_slab_t *sks) +{ + spl_kmem_obj_t *sko; + + ASSERT(skc->skc_magic == SKC_MAGIC); + ASSERT(sks->sks_magic == SKS_MAGIC); + + sko = list_entry(sks->sks_free_list.next, spl_kmem_obj_t, sko_list); + ASSERT(sko->sko_magic == SKO_MAGIC); + ASSERT(sko->sko_addr != NULL); + + /* Remove from sks_free_list */ + list_del_init(&sko->sko_list); + + sks->sks_age = jiffies; + sks->sks_ref++; + skc->skc_obj_alloc++; + + /* Track max obj usage statistics */ + if (skc->skc_obj_alloc > skc->skc_obj_max) + skc->skc_obj_max = skc->skc_obj_alloc; + + /* Track max slab usage statistics */ + if (sks->sks_ref == 1) { + skc->skc_slab_alloc++; + + if (skc->skc_slab_alloc > skc->skc_slab_max) + skc->skc_slab_max = skc->skc_slab_alloc; + } + + return (sko->sko_addr); +} + +/* + * Generic slab allocation function to run by the global work queues. + * It is responsible for allocating a new slab, linking it in to the list + * of partial slabs, and then waking any waiters. + */ +static int +__spl_cache_grow(spl_kmem_cache_t *skc, int flags) +{ + spl_kmem_slab_t *sks; + + fstrans_cookie_t cookie = spl_fstrans_mark(); + sks = spl_slab_alloc(skc, flags); + spl_fstrans_unmark(cookie); + + spin_lock(&skc->skc_lock); + if (sks) { + skc->skc_slab_total++; + skc->skc_obj_total += sks->sks_objs; + list_add_tail(&sks->sks_list, &skc->skc_partial_list); + + smp_mb__before_atomic(); + clear_bit(KMC_BIT_DEADLOCKED, &skc->skc_flags); + smp_mb__after_atomic(); + wake_up_all(&skc->skc_waitq); + } + spin_unlock(&skc->skc_lock); + + return (sks == NULL ? -ENOMEM : 0); +} + +static void +spl_cache_grow_work(void *data) +{ + spl_kmem_alloc_t *ska = (spl_kmem_alloc_t *)data; + spl_kmem_cache_t *skc = ska->ska_cache; + + (void) __spl_cache_grow(skc, ska->ska_flags); + + atomic_dec(&skc->skc_ref); + smp_mb__before_atomic(); + clear_bit(KMC_BIT_GROWING, &skc->skc_flags); + smp_mb__after_atomic(); + + kfree(ska); +} + +/* + * Returns non-zero when a new slab should be available. + */ +static int +spl_cache_grow_wait(spl_kmem_cache_t *skc) +{ + return (!test_bit(KMC_BIT_GROWING, &skc->skc_flags)); +} + +/* + * No available objects on any slabs, create a new slab. Note that this + * functionality is disabled for KMC_SLAB caches which are backed by the + * Linux slab. + */ +static int +spl_cache_grow(spl_kmem_cache_t *skc, int flags, void **obj) +{ + int remaining, rc = 0; + + ASSERT0(flags & ~KM_PUBLIC_MASK); + ASSERT(skc->skc_magic == SKC_MAGIC); + ASSERT((skc->skc_flags & KMC_SLAB) == 0); + might_sleep(); + *obj = NULL; + + /* + * Before allocating a new slab wait for any reaping to complete and + * then return so the local magazine can be rechecked for new objects. + */ + if (test_bit(KMC_BIT_REAPING, &skc->skc_flags)) { + rc = spl_wait_on_bit(&skc->skc_flags, KMC_BIT_REAPING, + TASK_UNINTERRUPTIBLE); + return (rc ? rc : -EAGAIN); + } + + /* + * To reduce the overhead of context switch and improve NUMA locality, + * it tries to allocate a new slab in the current process context with + * KM_NOSLEEP flag. If it fails, it will launch a new taskq to do the + * allocation. + * + * However, this can't be applied to KVM_VMEM due to a bug that + * __vmalloc() doesn't honor gfp flags in page table allocation. + */ + if (!(skc->skc_flags & KMC_VMEM)) { + rc = __spl_cache_grow(skc, flags | KM_NOSLEEP); + if (rc == 0) + return (0); + } + + /* + * This is handled by dispatching a work request to the global work + * queue. This allows us to asynchronously allocate a new slab while + * retaining the ability to safely fall back to a smaller synchronous + * allocations to ensure forward progress is always maintained. + */ + if (test_and_set_bit(KMC_BIT_GROWING, &skc->skc_flags) == 0) { + spl_kmem_alloc_t *ska; + + ska = kmalloc(sizeof (*ska), kmem_flags_convert(flags)); + if (ska == NULL) { + clear_bit_unlock(KMC_BIT_GROWING, &skc->skc_flags); + smp_mb__after_atomic(); + wake_up_all(&skc->skc_waitq); + return (-ENOMEM); + } + + atomic_inc(&skc->skc_ref); + ska->ska_cache = skc; + ska->ska_flags = flags; + taskq_init_ent(&ska->ska_tqe); + taskq_dispatch_ent(spl_kmem_cache_taskq, + spl_cache_grow_work, ska, 0, &ska->ska_tqe); + } + + /* + * The goal here is to only detect the rare case where a virtual slab + * allocation has deadlocked. We must be careful to minimize the use + * of emergency objects which are more expensive to track. Therefore, + * we set a very long timeout for the asynchronous allocation and if + * the timeout is reached the cache is flagged as deadlocked. From + * this point only new emergency objects will be allocated until the + * asynchronous allocation completes and clears the deadlocked flag. + */ + if (test_bit(KMC_BIT_DEADLOCKED, &skc->skc_flags)) { + rc = spl_emergency_alloc(skc, flags, obj); + } else { + remaining = wait_event_timeout(skc->skc_waitq, + spl_cache_grow_wait(skc), HZ / 10); + + if (!remaining) { + spin_lock(&skc->skc_lock); + if (test_bit(KMC_BIT_GROWING, &skc->skc_flags)) { + set_bit(KMC_BIT_DEADLOCKED, &skc->skc_flags); + skc->skc_obj_deadlock++; + } + spin_unlock(&skc->skc_lock); + } + + rc = -ENOMEM; + } + + return (rc); +} + +/* + * Refill a per-cpu magazine with objects from the slabs for this cache. + * Ideally the magazine can be repopulated using existing objects which have + * been released, however if we are unable to locate enough free objects new + * slabs of objects will be created. On success NULL is returned, otherwise + * the address of a single emergency object is returned for use by the caller. + */ +static void * +spl_cache_refill(spl_kmem_cache_t *skc, spl_kmem_magazine_t *skm, int flags) +{ + spl_kmem_slab_t *sks; + int count = 0, rc, refill; + void *obj = NULL; + + ASSERT(skc->skc_magic == SKC_MAGIC); + ASSERT(skm->skm_magic == SKM_MAGIC); + + refill = MIN(skm->skm_refill, skm->skm_size - skm->skm_avail); + spin_lock(&skc->skc_lock); + + while (refill > 0) { + /* No slabs available we may need to grow the cache */ + if (list_empty(&skc->skc_partial_list)) { + spin_unlock(&skc->skc_lock); + + local_irq_enable(); + rc = spl_cache_grow(skc, flags, &obj); + local_irq_disable(); + + /* Emergency object for immediate use by caller */ + if (rc == 0 && obj != NULL) + return (obj); + + if (rc) + goto out; + + /* Rescheduled to different CPU skm is not local */ + if (skm != skc->skc_mag[smp_processor_id()]) + goto out; + + /* + * Potentially rescheduled to the same CPU but + * allocations may have occurred from this CPU while + * we were sleeping so recalculate max refill. + */ + refill = MIN(refill, skm->skm_size - skm->skm_avail); + + spin_lock(&skc->skc_lock); + continue; + } + + /* Grab the next available slab */ + sks = list_entry((&skc->skc_partial_list)->next, + spl_kmem_slab_t, sks_list); + ASSERT(sks->sks_magic == SKS_MAGIC); + ASSERT(sks->sks_ref < sks->sks_objs); + ASSERT(!list_empty(&sks->sks_free_list)); + + /* + * Consume as many objects as needed to refill the requested + * cache. We must also be careful not to overfill it. + */ + while (sks->sks_ref < sks->sks_objs && refill-- > 0 && + ++count) { + ASSERT(skm->skm_avail < skm->skm_size); + ASSERT(count < skm->skm_size); + skm->skm_objs[skm->skm_avail++] = + spl_cache_obj(skc, sks); + } + + /* Move slab to skc_complete_list when full */ + if (sks->sks_ref == sks->sks_objs) { + list_del(&sks->sks_list); + list_add(&sks->sks_list, &skc->skc_complete_list); + } + } + + spin_unlock(&skc->skc_lock); +out: + return (NULL); +} + +/* + * Release an object back to the slab from which it came. + */ +static void +spl_cache_shrink(spl_kmem_cache_t *skc, void *obj) +{ + spl_kmem_slab_t *sks = NULL; + spl_kmem_obj_t *sko = NULL; + + ASSERT(skc->skc_magic == SKC_MAGIC); + + sko = spl_sko_from_obj(skc, obj); + ASSERT(sko->sko_magic == SKO_MAGIC); + sks = sko->sko_slab; + ASSERT(sks->sks_magic == SKS_MAGIC); + ASSERT(sks->sks_cache == skc); + list_add(&sko->sko_list, &sks->sks_free_list); + + sks->sks_age = jiffies; + sks->sks_ref--; + skc->skc_obj_alloc--; + + /* + * Move slab to skc_partial_list when no longer full. Slabs + * are added to the head to keep the partial list is quasi-full + * sorted order. Fuller at the head, emptier at the tail. + */ + if (sks->sks_ref == (sks->sks_objs - 1)) { + list_del(&sks->sks_list); + list_add(&sks->sks_list, &skc->skc_partial_list); + } + + /* + * Move empty slabs to the end of the partial list so + * they can be easily found and freed during reclamation. + */ + if (sks->sks_ref == 0) { + list_del(&sks->sks_list); + list_add_tail(&sks->sks_list, &skc->skc_partial_list); + skc->skc_slab_alloc--; + } +} + +/* + * Allocate an object from the per-cpu magazine, or if the magazine + * is empty directly allocate from a slab and repopulate the magazine. + */ +void * +spl_kmem_cache_alloc(spl_kmem_cache_t *skc, int flags) +{ + spl_kmem_magazine_t *skm; + void *obj = NULL; + + ASSERT0(flags & ~KM_PUBLIC_MASK); + ASSERT(skc->skc_magic == SKC_MAGIC); + ASSERT(!test_bit(KMC_BIT_DESTROY, &skc->skc_flags)); + + /* + * Allocate directly from a Linux slab. All optimizations are left + * to the underlying cache we only need to guarantee that KM_SLEEP + * callers will never fail. + */ + if (skc->skc_flags & KMC_SLAB) { + struct kmem_cache *slc = skc->skc_linux_cache; + do { + obj = kmem_cache_alloc(slc, kmem_flags_convert(flags)); + } while ((obj == NULL) && !(flags & KM_NOSLEEP)); + + goto ret; + } + + local_irq_disable(); + +restart: + /* + * Safe to update per-cpu structure without lock, but + * in the restart case we must be careful to reacquire + * the local magazine since this may have changed + * when we need to grow the cache. + */ + skm = skc->skc_mag[smp_processor_id()]; + ASSERT(skm->skm_magic == SKM_MAGIC); + + if (likely(skm->skm_avail)) { + /* Object available in CPU cache, use it */ + obj = skm->skm_objs[--skm->skm_avail]; + skm->skm_age = jiffies; + } else { + obj = spl_cache_refill(skc, skm, flags); + if ((obj == NULL) && !(flags & KM_NOSLEEP)) + goto restart; + + local_irq_enable(); + goto ret; + } + + local_irq_enable(); + ASSERT(obj); + ASSERT(IS_P2ALIGNED(obj, skc->skc_obj_align)); + +ret: + /* Pre-emptively migrate object to CPU L1 cache */ + if (obj) { + if (obj && skc->skc_ctor) + skc->skc_ctor(obj, skc->skc_private, flags); + else + prefetchw(obj); + } + + return (obj); +} +EXPORT_SYMBOL(spl_kmem_cache_alloc); + +/* + * Free an object back to the local per-cpu magazine, there is no + * guarantee that this is the same magazine the object was originally + * allocated from. We may need to flush entire from the magazine + * back to the slabs to make space. + */ +void +spl_kmem_cache_free(spl_kmem_cache_t *skc, void *obj) +{ + spl_kmem_magazine_t *skm; + unsigned long flags; + int do_reclaim = 0; + int do_emergency = 0; + + ASSERT(skc->skc_magic == SKC_MAGIC); + ASSERT(!test_bit(KMC_BIT_DESTROY, &skc->skc_flags)); + + /* + * Run the destructor + */ + if (skc->skc_dtor) + skc->skc_dtor(obj, skc->skc_private); + + /* + * Free the object from the Linux underlying Linux slab. + */ + if (skc->skc_flags & KMC_SLAB) { + kmem_cache_free(skc->skc_linux_cache, obj); + return; + } + + /* + * While a cache has outstanding emergency objects all freed objects + * must be checked. However, since emergency objects will never use + * a virtual address these objects can be safely excluded as an + * optimization. + */ + if (!is_vmalloc_addr(obj)) { + spin_lock(&skc->skc_lock); + do_emergency = (skc->skc_obj_emergency > 0); + spin_unlock(&skc->skc_lock); + + if (do_emergency && (spl_emergency_free(skc, obj) == 0)) + return; + } + + local_irq_save(flags); + + /* + * Safe to update per-cpu structure without lock, but + * no remote memory allocation tracking is being performed + * it is entirely possible to allocate an object from one + * CPU cache and return it to another. + */ + skm = skc->skc_mag[smp_processor_id()]; + ASSERT(skm->skm_magic == SKM_MAGIC); + + /* + * Per-CPU cache full, flush it to make space for this object, + * this may result in an empty slab which can be reclaimed once + * interrupts are re-enabled. + */ + if (unlikely(skm->skm_avail >= skm->skm_size)) { + spl_cache_flush(skc, skm, skm->skm_refill); + do_reclaim = 1; + } + + /* Available space in cache, use it */ + skm->skm_objs[skm->skm_avail++] = obj; + + local_irq_restore(flags); + + if (do_reclaim) + spl_slab_reclaim(skc); +} +EXPORT_SYMBOL(spl_kmem_cache_free); + +/* + * The generic shrinker function for all caches. Under Linux a shrinker + * may not be tightly coupled with a slab cache. In fact Linux always + * systematically tries calling all registered shrinker callbacks which + * report that they contain unused objects. Because of this we only + * register one shrinker function in the shim layer for all slab caches. + * We always attempt to shrink all caches when this generic shrinker + * is called. + * + * If sc->nr_to_scan is zero, the caller is requesting a query of the + * number of objects which can potentially be freed. If it is nonzero, + * the request is to free that many objects. + * + * Linux kernels >= 3.12 have the count_objects and scan_objects callbacks + * in struct shrinker and also require the shrinker to return the number + * of objects freed. + * + * Older kernels require the shrinker to return the number of freeable + * objects following the freeing of nr_to_free. + * + * Linux semantics differ from those under Solaris, which are to + * free all available objects which may (and probably will) be more + * objects than the requested nr_to_scan. + */ +static spl_shrinker_t +__spl_kmem_cache_generic_shrinker(struct shrinker *shrink, + struct shrink_control *sc) +{ + spl_kmem_cache_t *skc; + int alloc = 0; + + /* + * No shrinking in a transaction context. Can cause deadlocks. + */ + if (sc->nr_to_scan && spl_fstrans_check()) + return (SHRINK_STOP); + + down_read(&spl_kmem_cache_sem); + list_for_each_entry(skc, &spl_kmem_cache_list, skc_list) { + if (sc->nr_to_scan) { +#ifdef HAVE_SPLIT_SHRINKER_CALLBACK + uint64_t oldalloc = skc->skc_obj_alloc; + spl_kmem_cache_reap_now(skc, + MAX(sc->nr_to_scan>>fls64(skc->skc_slab_objs), 1)); + if (oldalloc > skc->skc_obj_alloc) + alloc += oldalloc - skc->skc_obj_alloc; +#else + spl_kmem_cache_reap_now(skc, + MAX(sc->nr_to_scan>>fls64(skc->skc_slab_objs), 1)); + alloc += skc->skc_obj_alloc; +#endif /* HAVE_SPLIT_SHRINKER_CALLBACK */ + } else { + /* Request to query number of freeable objects */ + alloc += skc->skc_obj_alloc; + } + } + up_read(&spl_kmem_cache_sem); + + /* + * When KMC_RECLAIM_ONCE is set allow only a single reclaim pass. + * This functionality only exists to work around a rare issue where + * shrink_slabs() is repeatedly invoked by many cores causing the + * system to thrash. + */ + if ((spl_kmem_cache_reclaim & KMC_RECLAIM_ONCE) && sc->nr_to_scan) + return (SHRINK_STOP); + + return (MAX(alloc, 0)); +} + +SPL_SHRINKER_CALLBACK_WRAPPER(spl_kmem_cache_generic_shrinker); + +/* + * Call the registered reclaim function for a cache. Depending on how + * many and which objects are released it may simply repopulate the + * local magazine which will then need to age-out. Objects which cannot + * fit in the magazine we will be released back to their slabs which will + * also need to age out before being release. This is all just best + * effort and we do not want to thrash creating and destroying slabs. + */ +void +spl_kmem_cache_reap_now(spl_kmem_cache_t *skc, int count) +{ + ASSERT(skc->skc_magic == SKC_MAGIC); + ASSERT(!test_bit(KMC_BIT_DESTROY, &skc->skc_flags)); + + atomic_inc(&skc->skc_ref); + + /* + * Execute the registered reclaim callback if it exists. + */ + if (skc->skc_flags & KMC_SLAB) { + if (skc->skc_reclaim) + skc->skc_reclaim(skc->skc_private); + goto out; + } + + /* + * Prevent concurrent cache reaping when contended. + */ + if (test_and_set_bit(KMC_BIT_REAPING, &skc->skc_flags)) + goto out; + + /* + * When a reclaim function is available it may be invoked repeatedly + * until at least a single slab can be freed. This ensures that we + * do free memory back to the system. This helps minimize the chance + * of an OOM event when the bulk of memory is used by the slab. + * + * When free slabs are already available the reclaim callback will be + * skipped. Additionally, if no forward progress is detected despite + * a reclaim function the cache will be skipped to avoid deadlock. + * + * Longer term this would be the correct place to add the code which + * repacks the slabs in order minimize fragmentation. + */ + if (skc->skc_reclaim) { + uint64_t objects = UINT64_MAX; + int do_reclaim; + + do { + spin_lock(&skc->skc_lock); + do_reclaim = + (skc->skc_slab_total > 0) && + ((skc->skc_slab_total-skc->skc_slab_alloc) == 0) && + (skc->skc_obj_alloc < objects); + + objects = skc->skc_obj_alloc; + spin_unlock(&skc->skc_lock); + + if (do_reclaim) + skc->skc_reclaim(skc->skc_private); + + } while (do_reclaim); + } + + /* Reclaim from the magazine and free all now empty slabs. */ + if (spl_kmem_cache_expire & KMC_EXPIRE_MEM) { + spl_kmem_magazine_t *skm; + unsigned long irq_flags; + + local_irq_save(irq_flags); + skm = skc->skc_mag[smp_processor_id()]; + spl_cache_flush(skc, skm, skm->skm_avail); + local_irq_restore(irq_flags); + } + + spl_slab_reclaim(skc); + clear_bit_unlock(KMC_BIT_REAPING, &skc->skc_flags); + smp_mb__after_atomic(); + wake_up_bit(&skc->skc_flags, KMC_BIT_REAPING); +out: + atomic_dec(&skc->skc_ref); +} +EXPORT_SYMBOL(spl_kmem_cache_reap_now); + +/* + * Reap all free slabs from all registered caches. + */ +void +spl_kmem_reap(void) +{ + struct shrink_control sc; + + sc.nr_to_scan = KMC_REAP_CHUNK; + sc.gfp_mask = GFP_KERNEL; + + (void) __spl_kmem_cache_generic_shrinker(NULL, &sc); +} +EXPORT_SYMBOL(spl_kmem_reap); + +int +spl_kmem_cache_init(void) +{ + init_rwsem(&spl_kmem_cache_sem); + INIT_LIST_HEAD(&spl_kmem_cache_list); + spl_kmem_cache_taskq = taskq_create("spl_kmem_cache", + spl_kmem_cache_kmem_threads, maxclsyspri, + spl_kmem_cache_kmem_threads * 8, INT_MAX, + TASKQ_PREPOPULATE | TASKQ_DYNAMIC); + spl_register_shrinker(&spl_kmem_cache_shrinker); + + return (0); +} + +void +spl_kmem_cache_fini(void) +{ + spl_unregister_shrinker(&spl_kmem_cache_shrinker); + taskq_destroy(spl_kmem_cache_taskq); +} |