/* * 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 . * UCRL-CODE-235197 * * This file is part of the SPL, Solaris Porting Layer. * For details, see . * * 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 . */ #include #include #include #include #include #include #include #include #include #include /* * 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. */ 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"); /* * 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); ASSERT(spin_is_locked(&skc->skc_lock)); /* * 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); ASSERT(spin_is_locked(&skc->skc_lock)); 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 skc->skc_linux_cache = kmem_cache_create( skc->skc_name, size, align, slabflags, NULL); 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); ASSERT(spin_is_locked(&skc->skc_lock)); 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); ASSERT(spin_is_locked(&skc->skc_lock)); 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); }