diff options
| -rw-r--r-- | include/linux/mm_types.h | 89 | ||||
| -rw-r--r-- | include/linux/page-flags.h | 5 | ||||
| -rw-r--r-- | include/linux/slub_def.h | 3 | ||||
| -rw-r--r-- | mm/slub.c | 764 | ||||
| -rw-r--r-- | tools/slub/slabinfo.c | 59 |
5 files changed, 616 insertions, 304 deletions
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 027935c86c68..774b8952deb4 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -30,23 +30,61 @@ struct address_space; * moment. Note that we have no way to track which tasks are using * a page, though if it is a pagecache page, rmap structures can tell us * who is mapping it. + * + * The objects in struct page are organized in double word blocks in + * order to allows us to use atomic double word operations on portions + * of struct page. That is currently only used by slub but the arrangement + * allows the use of atomic double word operations on the flags/mapping + * and lru list pointers also. */ struct page { + /* First double word block */ unsigned long flags; /* Atomic flags, some possibly * updated asynchronously */ - atomic_t _count; /* Usage count, see below. */ - union { - atomic_t _mapcount; /* Count of ptes mapped in mms, - * to show when page is mapped - * & limit reverse map searches. + struct address_space *mapping; /* If low bit clear, points to + * inode address_space, or NULL. + * If page mapped as anonymous + * memory, low bit is set, and + * it points to anon_vma object: + * see PAGE_MAPPING_ANON below. */ - struct { /* SLUB */ - u16 inuse; - u16 objects; + /* Second double word */ + struct { + union { + pgoff_t index; /* Our offset within mapping. */ + void *freelist; /* slub first free object */ + }; + + union { + /* Used for cmpxchg_double in slub */ + unsigned long counters; + + struct { + + union { + atomic_t _mapcount; /* Count of ptes mapped in mms, + * to show when page is mapped + * & limit reverse map searches. + */ + + struct { + unsigned inuse:16; + unsigned objects:15; + unsigned frozen:1; + }; + }; + atomic_t _count; /* Usage count, see below. */ + }; }; }; + + /* Third double word block */ + struct list_head lru; /* Pageout list, eg. active_list + * protected by zone->lru_lock ! + */ + + /* Remainder is not double word aligned */ union { - struct { unsigned long private; /* Mapping-private opaque data: * usually used for buffer_heads * if PagePrivate set; used for @@ -54,27 +92,13 @@ struct page { * indicates order in the buddy * system if PG_buddy is set. */ - struct address_space *mapping; /* If low bit clear, points to - * inode address_space, or NULL. - * If page mapped as anonymous - * memory, low bit is set, and - * it points to anon_vma object: - * see PAGE_MAPPING_ANON below. - */ - }; #if USE_SPLIT_PTLOCKS - spinlock_t ptl; + spinlock_t ptl; #endif - struct kmem_cache *slab; /* SLUB: Pointer to slab */ - struct page *first_page; /* Compound tail pages */ - }; - union { - pgoff_t index; /* Our offset within mapping. */ - void *freelist; /* SLUB: freelist req. slab lock */ + struct kmem_cache *slab; /* SLUB: Pointer to slab */ + struct page *first_page; /* Compound tail pages */ }; - struct list_head lru; /* Pageout list, eg. active_list - * protected by zone->lru_lock ! - */ + /* * On machines where all RAM is mapped into kernel address space, * we can simply calculate the virtual address. On machines with @@ -100,7 +124,16 @@ struct page { */ void *shadow; #endif -}; +} +/* + * If another subsystem starts using the double word pairing for atomic + * operations on struct page then it must change the #if to ensure + * proper alignment of the page struct. + */ +#if defined(CONFIG_SLUB) && defined(CONFIG_CMPXCHG_LOCAL) + __attribute__((__aligned__(2*sizeof(unsigned long)))) +#endif +; typedef unsigned long __nocast vm_flags_t; diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 3e5a1b189a41..e90a673be67e 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -124,9 +124,6 @@ enum pageflags { /* SLOB */ PG_slob_free = PG_private, - - /* SLUB */ - PG_slub_frozen = PG_active, }; #ifndef __GENERATING_BOUNDS_H @@ -212,8 +209,6 @@ PAGEFLAG(SwapBacked, swapbacked) __CLEARPAGEFLAG(SwapBacked, swapbacked) __PAGEFLAG(SlobFree, slob_free) -__PAGEFLAG(SlubFrozen, slub_frozen) - /* * Private page markings that may be used by the filesystem that owns the page * for its own purposes. diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h index 4b35c06dfbc5..f58d6413d230 100644 --- a/include/linux/slub_def.h +++ b/include/linux/slub_def.h @@ -24,6 +24,7 @@ enum stat_item { ALLOC_FROM_PARTIAL, /* Cpu slab acquired from partial list */ ALLOC_SLAB, /* Cpu slab acquired from page allocator */ ALLOC_REFILL, /* Refill cpu slab from slab freelist */ + ALLOC_NODE_MISMATCH, /* Switching cpu slab */ FREE_SLAB, /* Slab freed to the page allocator */ CPUSLAB_FLUSH, /* Abandoning of the cpu slab */ DEACTIVATE_FULL, /* Cpu slab was full when deactivated */ @@ -31,8 +32,10 @@ enum stat_item { DEACTIVATE_TO_HEAD, /* Cpu slab was moved to the head of partials */ DEACTIVATE_TO_TAIL, /* Cpu slab was moved to the tail of partials */ DEACTIVATE_REMOTE_FREES,/* Slab contained remotely freed objects */ + DEACTIVATE_BYPASS, /* Implicit deactivation */ ORDER_FALLBACK, /* Number of times fallback was necessary */ CMPXCHG_DOUBLE_CPU_FAIL,/* Failure of this_cpu_cmpxchg_double */ + CMPXCHG_DOUBLE_FAIL, /* Number of times that cmpxchg double did not match */ NR_SLUB_STAT_ITEMS }; struct kmem_cache_cpu { diff --git a/mm/slub.c b/mm/slub.c index f8f5e8efeb88..eb5a8f93338a 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2,10 +2,11 @@ * SLUB: A slab allocator that limits cache line use instead of queuing * objects in per cpu and per node lists. * - * The allocator synchronizes using per slab locks and only - * uses a centralized lock to manage a pool of partial slabs. + * The allocator synchronizes using per slab locks or atomic operatios + * and only uses a centralized lock to manage a pool of partial slabs. * * (C) 2007 SGI, Christoph Lameter + * (C) 2011 Linux Foundation, Christoph Lameter */ #include <linux/mm.h> @@ -33,15 +34,27 @@ /* * Lock order: - * 1. slab_lock(page) - * 2. slab->list_lock + * 1. slub_lock (Global Semaphore) + * 2. node->list_lock + * 3. slab_lock(page) (Only on some arches and for debugging) * - * The slab_lock protects operations on the object of a particular - * slab and its metadata in the page struct. If the slab lock - * has been taken then no allocations nor frees can be performed - * on the objects in the slab nor can the slab be added or removed - * from the partial or full lists since this would mean modifying - * the page_struct of the slab. + * slub_lock + * + * The role of the slub_lock is to protect the list of all the slabs + * and to synchronize major metadata changes to slab cache structures. + * + * The slab_lock is only used for debugging and on arches that do not + * have the ability to do a cmpxchg_double. It only protects the second + * double word in the page struct. Meaning + * A. page->freelist -> List of object free in a page + * B. page->counters -> Counters of objects + * C. page->frozen -> frozen state + * + * If a slab is frozen then it is exempt from list management. It is not + * on any list. The processor that froze the slab is the one who can + * perform list operations on the page. Other processors may put objects + * onto the freelist but the processor that froze the slab is the only + * one that can retrieve the objects from the page's freelist. * * The list_lock protects the partial and full list on each node and * the partial slab counter. If taken then no new slabs may be added or @@ -54,20 +67,6 @@ * slabs, operations can continue without any centralized lock. F.e. * allocating a long series of objects that fill up slabs does not require * the list lock. - * - * The lock order is sometimes inverted when we are trying to get a slab - * off a list. We take the list_lock and then look for a page on the list - * to use. While we do that objects in the slabs may be freed. We can - * only operate on the slab if we have also taken the slab_lock. So we use - * a slab_trylock() on the slab. If trylock was successful then no frees - * can occur anymore and we can use the slab for allocations etc. If the - * slab_trylock() does not succeed then frees are in progress in the slab and - * we must stay away from it for a while since we may cause a bouncing - * cacheline if we try to acquire the lock. So go onto the next slab. - * If all pages are busy then we may allocate a new slab instead of reusing - * a partial slab. A new slab has no one operating on it and thus there is - * no danger of cacheline contention. - * * Interrupts are disabled during allocation and deallocation in order to * make the slab allocator safe to use in the context of an irq. In addition * interrupts are disabled to ensure that the processor does not change @@ -132,6 +131,9 @@ static inline int kmem_cache_debug(struct kmem_cache *s) /* Enable to test recovery from slab corruption on boot */ #undef SLUB_RESILIENCY_TEST +/* Enable to log cmpxchg failures */ +#undef SLUB_DEBUG_CMPXCHG + /* * Mininum number of partial slabs. These will be left on the partial * lists even if they are empty. kmem_cache_shrink may reclaim them. @@ -167,10 +169,11 @@ static inline int kmem_cache_debug(struct kmem_cache *s) #define OO_SHIFT 16 #define OO_MASK ((1 << OO_SHIFT) - 1) -#define MAX_OBJS_PER_PAGE 65535 /* since page.objects is u16 */ +#define MAX_OBJS_PER_PAGE 32767 /* since page.objects is u15 */ /* Internal SLUB flags */ #define __OBJECT_POISON 0x80000000UL /* Poison object */ +#define __CMPXCHG_DOUBLE 0x40000000UL /* Use cmpxchg_double */ static int kmem_size = sizeof(struct kmem_cache); @@ -343,11 +346,99 @@ static inline int oo_objects(struct kmem_cache_order_objects x) return x.x & OO_MASK; } +/* + * Per slab locking using the pagelock + */ +static __always_inline void slab_lock(struct page *page) +{ + bit_spin_lock(PG_locked, &page->flags); +} + +static __always_inline void slab_unlock(struct page *page) +{ + __bit_spin_unlock(PG_locked, &page->flags); +} + +/* Interrupts must be disabled (for the fallback code to work right) */ +static inline bool __cmpxchg_double_slab(struct kmem_cache *s, struct page *page, + void *freelist_old, unsigned long counters_old, + void *freelist_new, unsigned long counters_new, + const char *n) +{ + VM_BUG_ON(!irqs_disabled()); +#ifdef CONFIG_CMPXCHG_DOUBLE + if (s->flags & __CMPXCHG_DOUBLE) { + if (cmpxchg_double(&page->freelist, + freelist_old, counters_old, + freelist_new, counters_new)) + return 1; + } else +#endif + { + slab_lock(page); + if (page->freelist == freelist_old && page->counters == counters_old) { + page->freelist = freelist_new; + page->counters = counters_new; + slab_unlock(page); + return 1; + } + slab_unlock(page); + } + + cpu_relax(); + stat(s, CMPXCHG_DOUBLE_FAIL); + +#ifdef SLUB_DEBUG_CMPXCHG + printk(KERN_INFO "%s %s: cmpxchg double redo ", n, s->name); +#endif + + return 0; +} + +static inline bool cmpxchg_double_slab(struct kmem_cache *s, struct page *page, + void *freelist_old, unsigned long counters_old, + void *freelist_new, unsigned long counters_new, + const char *n) +{ +#ifdef CONFIG_CMPXCHG_DOUBLE + if (s->flags & __CMPXCHG_DOUBLE) { + if (cmpxchg_double(&page->freelist, + freelist_old, counters_old, + freelist_new, counters_new)) + return 1; + } else +#endif + { + unsigned long flags; + + local_irq_save(flags); + slab_lock(page); + if (page->freelist == freelist_old && page->counters == counters_old) { + page->freelist = freelist_new; + page->counters = counters_new; + slab_unlock(page); + local_irq_restore(flags); + return 1; + } + slab_unlock(page); + local_irq_restore(flags); + } + + cpu_relax(); + stat(s, CMPXCHG_DOUBLE_FAIL); + +#ifdef SLUB_DEBUG_CMPXCHG + printk(KERN_INFO "%s %s: cmpxchg double redo ", n, s->name); +#endif + + return 0; +} + #ifdef CONFIG_SLUB_DEBUG /* * Determine a map of object in use on a page. * - * Slab lock or node listlock must be held to guarantee that the page does + * Node listlock must be held to guarantee that the page does * not vanish from under us. */ static void get_map(struct kmem_cache *s, struct page *page, unsigned long *map) @@ -838,10 +929,11 @@ static int check_slab(struct kmem_cache *s, struct page *page) static int on_freelist(struct kmem_cache *s, struct page *page, void *search) { int nr = 0; - void *fp = page->freelist; + void *fp; void *object = NULL; unsigned long max_objects; + fp = page->freelist; while (fp && nr <= page->objects) { if (fp == search) return 1; @@ -946,26 +1038,27 @@ static inline void slab_free_hook(struct kmem_cache *s, void *x) /* * Tracking of fully allocated slabs for debugging purposes. + * + * list_lock must be held. */ -static void add_full(struct kmem_cache_node *n, struct page *page) +static void add_full(struct kmem_cache *s, + struct kmem_cache_node *n, struct page *page) { - spin_lock(&n->list_lock); + if (!(s->flags & SLAB_STORE_USER)) + return; + list_add(&page->lru, &n->full); - spin_unlock(&n->list_lock); } +/* + * list_lock must be held. + */ static void remove_full(struct kmem_cache *s, struct page *page) { - struct kmem_cache_node *n; - if (!(s->flags & SLAB_STORE_USER)) return; - n = get_node(s, page_to_nid(page)); - - spin_lock(&n->list_lock); list_del(&page->lru); - spin_unlock(&n->list_lock); } /* Tracking of the number of slabs for debugging purposes */ @@ -1021,11 +1114,6 @@ static noinline int alloc_debug_processing(struct kmem_cache *s, struct page *pa if (!check_slab(s, page)) goto bad; - if (!on_freelist(s, page, object)) { - object_err(s, page, object, "Object already allocated"); - goto bad; - } - if (!check_valid_pointer(s, page, object)) { object_err(s, page, object, "Freelist Pointer check fails"); goto bad; @@ -1058,6 +1146,12 @@ bad: static noinline int free_debug_processing(struct kmem_cache *s, struct page *page, void *object, unsigned long addr) { + unsigned long flags; + int rc = 0; + + local_irq_save(flags); + slab_lock(page); + if (!check_slab(s, page)) goto fail; @@ -1072,7 +1166,7 @@ static noinline int free_debug_processing(struct kmem_cache *s, } if (!check_object(s, page, object, SLUB_RED_ACTIVE)) - return 0; + goto out; if (unlikely(s != page->slab)) { if (!PageSlab(page)) { @@ -1089,18 +1183,19 @@ static noinline int free_debug_processing(struct kmem_cache *s, goto fail; } - /* Special debug activities for freeing objects */ - if (!PageSlubFrozen(page) && !page->freelist) - remove_full(s, page); if (s->flags & SLAB_STORE_USER) set_track(s, object, TRACK_FREE, addr); trace(s, page, object, 0); init_object(s, object, SLUB_RED_INACTIVE); - return 1; + rc = 1; +out: + slab_unlock(page); + local_irq_restore(flags); + return rc; fail: slab_fix(s, "Object at 0x%p not freed", object); - return 0; + goto out; } static int __init setup_slub_debug(char *str) @@ -1200,7 +1295,9 @@ static inline int slab_pad_check(struct kmem_cache *s, struct page *page) { return 1; } static inline int check_object(struct kmem_cache *s, struct page *page, void *object, u8 val) { return 1; } -static inline void add_full(struct kmem_cache_node *n, struct page *page) {} +static inline void add_full(struct kmem_cache *s, struct kmem_cache_node *n, + struct page *page) {} +static inline void remove_full(struct kmem_cache *s, struct page *page) {} static inline unsigned long kmem_cache_flags(unsigned long objsize, unsigned long flags, const char *name, void (*ctor)(void *)) @@ -1252,6 +1349,11 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node) struct kmem_cache_order_objects oo = s->oo; gfp_t alloc_gfp; + flags &= gfp_allowed_mask; + + if (flags & __GFP_WAIT) + local_irq_enable(); + flags |= s->allocflags; /* @@ -1268,12 +1370,17 @@ static struct page *allocate_slab(struct kmem_cache *s, gfp_t flags, int node) * Try a lower order alloc if possible */ page = alloc_slab_page(flags, node, oo); - if (!page) - return NULL; - stat(s, ORDER_FALLBACK); + if (page) + stat(s, ORDER_FALLBACK); } + if (flags & __GFP_WAIT) + local_irq_disable(); + + if (!page) + return NULL; + if (kmemcheck_enabled && !(s->flags & (SLAB_NOTRACK | DEBUG_DEFAULT_FLAGS))) { int pages = 1 << oo_order(oo); @@ -1341,6 +1448,7 @@ static struct page *new_slab(struct kmem_cache *s, gfp_t flags, int node) page->freelist = start; page->inuse = 0; + page->frozen = 1; out: return page; } @@ -1418,77 +1526,87 @@ static void discard_slab(struct kmem_cache *s, struct page *page) } /* - * Per slab locking using the pagelock - */ -static __always_inline void slab_lock(struct page *page) -{ - bit_spin_lock(PG_locked, &page->flags); -} - -static __always_inline void slab_unlock(struct page *page) -{ - __bit_spin_unlock(PG_locked, &page->flags); -} - -static __always_inline int slab_trylock(struct page *page) -{ - int rc = 1; - - rc = bit_spin_trylock(PG_locked, &page->flags); - return rc; -} - -/* - * Management of partially allocated slabs + * Management of partially allocated slabs. + * + * list_lock must be held. */ -static void add_partial(struct kmem_cache_node *n, +static inline void add_partial(struct kmem_cache_node *n, struct page *page, int tail) { - spin_lock(&n->list_lock); n->nr_partial++; if (tail) list_add_tail(&page->lru, &n->partial); else list_add(&page->lru, &n->partial); - spin_unlock(&n->list_lock); } -static inline void __remove_partial(struct kmem_cache_node *n, +/* + * list_lock must be held. + */ +static inline void remove_partial(struct kmem_cache_node *n, struct page *page) { list_del(&page->lru); n->nr_partial--; } -static void remove_partial(struct kmem_cache *s, struct page *page) -{ - struct kmem_cache_node *n = get_node(s, page_to_nid(page)); - - spin_lock(&n->list_lock); - __remove_partial(n, page); - spin_unlock(&n->list_lock); -} - /* - * Lock slab and remove from the partial list. + * Lock slab, remove from the partial list and put the object into the + * per cpu freelist. * * Must hold list_lock. */ -static inline int lock_and_freeze_slab(struct kmem_cache_node *n, - struct page *page) +static inline int acquire_slab(struct kmem_cache *s, + struct kmem_cache_node *n, struct page *page) { - if (slab_trylock(page)) { - __remove_partial(n, page); - __SetPageSlubFrozen(page); + void *freelist; + unsigned long counters; + struct page new; + + /* + * Zap the freelist and set the frozen bit. + * The old freelist is the list of objects for the + * per cpu allocation list. + */ + do { + freelist = page->freelist; + counters = page->counters; + new.counters = counters; + new.inuse = page->objects; + + VM_BUG_ON(new.frozen); + new.frozen = 1; + + } while (!__cmpxchg_double_slab(s, page, + freelist, counters, + NULL, new.counters, + "lock and freeze")); + + remove_partial(n, page); + + if (freelist) { + /* Populate the per cpu freelist */ + this_cpu_write(s->cpu_slab->freelist, freelist); + this_cpu_write(s->cpu_slab->page, page); + this_cpu_write(s->cpu_slab->node, page_to_nid(page)); return 1; + } else { + /* + * Slab page came from the wrong list. No object to allocate + * from. Put it onto the correct list and continue partial + * scan. + */ + printk(KERN_ERR "SLUB: %s : Page without available objects on" + " partial list\n", s->name); + return 0; } - return 0; } /* * Try to allocate a partial slab from a specific node. */ -static struct page *get_partial_node(struct kmem_cache_node *n) +static struct page *get_partial_node(struct kmem_cache *s, + struct kmem_cache_node *n) { struct page *page; @@ -1503,7 +1621,7 @@ static struct page *get_partial_node(struct kmem_cache_node *n) spin_lock(&n->list_lock); list_for_each_entry(page, &n->partial, lru) - if (lock_and_freeze_slab(n, page)) + if (acquire_slab(s, n, page)) goto out; page = NULL; out: @@ -1554,7 +1672,7 @@ static struct page *get_any_partial(struct kmem_cache *s, gfp_t flags) if (n && cpuset_zone_allowed_hardwall(zone, flags) && n->nr_partial > s->min_partial) { - page = get_partial_node(n); + page = get_partial_node(s, n); if (page) { put_mems_allowed(); return page; @@ -1574,60 +1692,13 @@ static struct page *get_partial(struct kmem_cache *s, gfp_t flags, int node) struct page *page; int searchnode = (node == NUMA_NO_NODE) ? numa_node_id() : node; - page = get_partial_node(get_node(s, searchnode)); + page = get_partial_node(s, get_node(s, searchnode)); if (page || node != NUMA_NO_NODE) return page; return get_any_partial(s, flags); } -/* - * Move a page back to the lists. - * - * Must be called with the slab lock held. - * - * On exit the slab lock will have been dropped. - */ -static void unfreeze_slab(struct kmem_cache *s, struct page *page, int tail) - __releases(bitlock) -{ - struct kmem_cache_node *n = get_node(s, page_to_nid(page)); - - __ClearPageSlubFrozen(page); - if (page->inuse) { - - if (page->freelist) { - add_partial(n, page, tail); - stat(s, tail ? DEACTIVATE_TO_TAIL : DEACTIVATE_TO_HEAD); - } else { - stat(s, DEACTIVATE_FULL); - if (kmem_cache_debug(s) && (s->flags & SLAB_STORE_USER)) - add_full(n, page); - } - slab_unlock(page); - } else { - stat(s, DEACTIVATE_EMPTY); - if (n->nr_partial < s->min_partial) { - /* - * Adding an empty slab to the partial slabs in order - * to avoid page allocator overhead. This slab needs - * to come after the other slabs with objects in - * so that the others get filled first. That way the - * size of the partial list stays small. - * - * kmem_cache_shrink can reclaim any empty slabs from - * the partial list. - */ - add_partial(n, page, 1); - slab_unlock(page); - } else { - slab_unlock(page); - stat(s, FREE_SLAB); - discard_slab(s, page); - } - } -} - #ifdef CONFIG_PREEMPT /* * Calculate the next globally unique transaction for disambiguiation @@ -1697,42 +1768,161 @@ void init_kmem_cache_cpus(struct kmem_cache *s) /* * Remove the cpu slab */ + +/* + * Remove the cpu slab + */ static void deactivate_slab(struct kmem_cache *s, struct kmem_cache_cpu *c) - __releases(bitlock) { + enum slab_modes { M_NONE, M_PARTIAL, M_FULL, M_FREE }; struct page *page = c->page; - int tail = 1; - - if (page->freelist) + struct kmem_cache_node *n = get_node(s, page_to_nid(page)); + int lock = 0; + enum slab_modes l = M_NONE, m = M_NONE; + void *freelist; + void *nextfree; + int tail = 0; + struct page new; + struct page old; + + if (page->freelist) { stat(s, DEACTIVATE_REMOTE_FREES); + tail = 1; + } + + c->tid = next_tid(c->tid); + c->page = NULL; + freelist = c->freelist; + c->freelist = NULL; + + /* + * Stage one: Free all available per cpu objects back + * to the page freelist while it is still frozen. Leave the + * last one. + * + * There is no need to take the list->lock because the page + * is still frozen. + */ + while (freelist && (nextfree = get_freepointer(s, freelist))) { + void *prior; + unsigned long counters; + + do { + prior = page->freelist; + counters = page->counters; + set_freepointer(s, freelist, prior); + new.counters = counters; + new.inuse--; + VM_BUG_ON(!new.frozen); + + } while (!__cmpxchg_double_slab(s, page, + prior, counters, + freelist, new.counters, + "drain percpu freelist")); + + freelist = nextfree; + } + /* - * Merge cpu freelist into slab freelist. Typically we get here - * because both freelists are empty. So this is unlikely - * to occur. + * Stage two: Ensure that the page is unfrozen while the + * list presence reflects the actual number of objects + * during unfreeze. + * + * We setup the list membership and then perform a cmpxchg + * with the count. If there is a mismatch then the page + * is not unfrozen but the page is on the wrong list. + * + * Then we restart the process which may have to remove + * the page from the list that we just put it on again + * because the number of objects in the slab may have + * changed. */ - while (unlikely(c->freelist)) { - void **object; +redo: - tail = 0; /* Hot objects. Put the slab first */ + old.freelist = page->freelist; + old.counters = page->counters; + VM_BUG_ON(!old.frozen); - /* Retrieve object from cpu_freelist */ - object = c->freelist; - c->freelist = get_freepointer(s, c->freelist); + /* Determine target state of the slab */ + new.counters = old.counters; + if (freelist) { + new.inuse--; + set_freepointer(s, freelist, old.freelist); + new.freelist = freelist; + } else + new.freelist = old.freelist; + + new.frozen = 0; + + if (!new.inuse && n->nr_partial < s->min_partial) + m = M_FREE; + else if (new.freelist) { + m = M_PARTIAL; + if (!lock) { + lock = 1; + /* + * Taking the spinlock removes the possiblity + * that acquire_slab() will see a slab page that + * is frozen + */ + spin_lock(&n->list_lock); + } + } else { + m = M_FULL; + if (kmem_cache_debug(s) && !lock) { + lock = 1; + /* + * This also ensures that the scanning of full + * slabs from diagnostic functions will not see + * any frozen slabs. + */ + spin_lock(&n->list_lock); + } + } + + if (l != m) { + + if (l == M_PARTIAL) + + remove_partial(n, page); + + else if (l == M_FULL) + + remove_full(s, page); + + if (m == M_PARTIAL) { + + add_partial(n, page, tail); + stat(s, tail ? DEACTIVATE_TO_TAIL : DEACTIVATE_TO_HEAD); + + } else if (m == M_FULL) { - /* And put onto the regular freelist */ - set_freepointer(s, object, page->freelist); - page->freelist = object; - page->inuse--; + stat(s, DEACTIVATE_FULL); + add_full(s, n, page); + + } + } + + l = m; + if (!__cmpxchg_double_slab(s, page, + old.freelist, old.counters, + new.freelist, new.counters, + "unfreezing slab")) + goto redo; + + if (lock) + spin_unlock(&n->list_lock); + + if (m == M_FREE) { + stat(s, DEACTIVATE_EMPTY); + discard_slab(s, page); + stat(s, FREE_SLAB); } - c->page = NULL; - c->tid = next_tid(c->tid); - unfreeze_slab(s, page, tail); } static inline void flush_slab(struct kmem_cache *s, struct kmem_cache_cpu *c) { stat(s, CPUSLAB_FLUSH); - slab_lock(c->page); deactivate_slab(s, c); } @@ -1861,6 +2051,8 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, void **object; struct page *page; unsigned long flags; + struct page new; + unsigned long counters; local_irq_save(flags); #ifdef CONFIG_PREEMPT @@ -1879,72 +2071,97 @@ static void *__slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node, if (!page) goto new_slab; - slab_lock(page); - if (unlikely(!node_match(c, node))) - goto another_slab; + if (unlikely(!node_match(c, node))) { + stat(s, ALLOC_NODE_MISMATCH); + deactivate_slab(s, c); + goto new_slab; + } + + stat(s, ALLOC_SLOWPATH); + + do { + object = page->freelist; + counters = page->counters; + new.counters = counters; + VM_BUG_ON(!new.frozen); + + /* + * If there is no object left then we use this loop to + * deactivate the slab which is simple since no objects + * are left in the slab and therefore we do not need to + * put the page back onto the partial list. + * + * If there are objects left then we retrieve them + * and use them to refill the per cpu queue. + */ + + new.inuse = page->objects; + new.frozen = object != NULL; + + } while (!__cmpxchg_double_slab(s, page, + object, counters, + NULL, new.counters, + "__slab_alloc")); + + if (unlikely(!object)) { + c->page = NULL; + stat(s, DEACTIVATE_BYPASS); + goto new_slab; + } stat(s, ALLOC_REFILL); load_freelist: - object = page->freelist; - if (unlikely(!object)) - goto another_slab; - if (kmem_cache_debug(s)) - goto debug; - + VM_BUG_ON(!page->frozen); c->freelist = get_freepointer(s, object); - page->inuse = page->objects; - page->freelist = NULL; - - slab_unlock(page); c->tid = next_tid(c->tid); local_irq_restore(flags); - stat(s, ALLOC_SLOWPATH); return object; -another_slab: - deactivate_slab(s, c); - new_slab: page = get_partial(s, gfpflags, node); if (page) { stat(s, ALLOC_FROM_PARTIAL); - c->node = page_to_nid(page); - c->page = page; + object = c->freelist; + + if (kmem_cache_debug(s)) + goto debug; goto load_freelist; } - gfpflags &= gfp_allowed_mask; - if (gfpflags & __GFP_WAIT) - local_irq_enable(); - page = new_slab(s, gfpflags, node); - if (gfpflags & __GFP_WAIT) - local_irq_disable(); - if (page) { c = __this_cpu_ptr(s->cpu_slab); - stat(s, ALLOC_SLAB); if (c->page) flush_slab(s, c); - slab_lock(page); - __SetPageSlubFrozen(page); + /* + * No other reference to the page yet so we can + * muck around with it freely without cmpxchg + */ + object = page->freelist; + page->freelist = NULL; + page->inuse = page->objects; + + stat(s, ALLOC_SLAB); c->node = page_to_nid(page); c->page = page; + + if (kmem_cache_debug(s)) + goto debug; goto load_freelist; } if (!(gfpflags & __GFP_NOWARN) && printk_ratelimit()) slab_out_of_memory(s, gfpflags, node); local_irq_restore(flags); return NULL; + debug: - if (!alloc_debug_processing(s, page, object, addr)) - goto another_slab; + if (!object || !alloc_debug_processing(s, page, object, addr)) + goto new_slab; - page->inuse++; - page->freelist = get_freepointer(s, object); + c->freelist = get_freepointer(s, object); deactivate_slab(s, c); c->page = NULL; c->node = NUMA_NO_NODE; @@ -2096,40 +2313,75 @@ static void __slab_free(struct kmem_cache *s, struct page *page, { void *prior; void **object = (void *)x; - unsigned long flags; + int was_frozen; + int inuse; + struct page new; + unsigned long counters; + struct kmem_cache_node *n = NULL; + unsigned long uninitialized_var(flags); - local_irq_save(flags); - slab_lock(page); stat(s, FREE_SLOWPATH); if (kmem_cache_debug(s) && !free_debug_processing(s, page, x, addr)) - goto out_unlock; + return; - prior = page->freelist; - set_freepointer(s, object, prior); - page->freelist = object; - page->inuse--; + do { + prior = page->freelist; + counters = page->counters; + set_freepointer(s, object, prior); + new.counters = counters; + was_frozen = new.frozen; + new.inuse--; + if ((!new.inuse || !prior) && !was_frozen && !n) { + n = get_node(s, page_to_nid(page)); + /* + * Speculatively acquire the list_lock. + * If the cmpxchg does not succeed then we may + * drop the list_lock without any processing. + * + * Otherwise the list_lock will synchronize with + * other processors updating the list of slabs. + */ + spin_lock_irqsave(&n->list_lock, flags); + } + inuse = new.inuse; - if (unlikely(PageSlubFrozen(page))) { - stat(s, FREE_FROZEN); - goto out_unlock; - } + } while (!cmpxchg_double_slab(s, page, + prior, counters, + object, new.counters, + "__slab_free")); - if (unlikely(!page->inuse)) - goto slab_empty; + if (likely(!n)) { + /* + * The list lock was not taken therefore no list + * activity can be necessary. + */ + if (was_frozen) + stat(s, FREE_FROZEN); + return; + } /* - * Objects left in the slab. If it was not on the partial list before - * then add it. + * was_frozen may have been set after we acquired the list_lock in + * an earlier loop. So we need to check it here again. */ - if (unlikely(!prior)) { - add_partial(get_node(s, page_to_nid(page)), page, 1); - stat(s, FREE_ADD_PARTIAL); - } + if (was_frozen) + stat(s, FREE_FROZEN); + else { + if (unlikely(!inuse && n->nr_partial > s->min_partial)) + goto slab_empty; -out_unlock: - slab_unlock(page); - local_irq_restore(flags); + /* + * Objects left in the slab. If it was not on the partial list before + * then add it. + */ + if (unlikely(!prior)) { + remove_full(s, page); + add_partial(n, page, 0); + stat(s, FREE_ADD_PARTIAL); + } + } + spin_unlock_irqrestore(&n->list_lock, flags); return; slab_empty: @@ -2137,11 +2389,11 @@ slab_empty: /* * Slab still on the partial list. */ - remove_partial(s, page); + remove_partial(n, page); stat(s, FREE_REMOVE_PARTIAL); } - slab_unlock(page); - local_irq_restore(flags); + + spin_unlock_irqrestore(&n->list_lock, flags); stat(s, FREE_SLAB); discard_slab(s, page); } @@ -2415,7 +2667,6 @@ static void early_kmem_cache_node_alloc(int node) { struct page *page; struct kmem_cache_node *n; - unsigned long flags; BUG_ON(kmem_cache_node->size < sizeof(struct kmem_cache_node)); @@ -2433,6 +2684,7 @@ static void early_kmem_cache_node_alloc(int node) BUG_ON(!n); page->freelist = get_freepointer(kmem_cache_node, n); page->inuse++; + page->frozen = 0; kmem_cache_node->node[node] = n; #ifdef CONFIG_SLUB_DEBUG init_object(kmem_cache_node, n, SLUB_RED_ACTIVE); @@ -2441,14 +2693,7 @@ static void early_kmem_cache_node_alloc(int node) init_kmem_cache_node(n, kmem_cache_node); inc_slabs_node(kmem_cache_node, node, page->objects); - /* - * lockdep requires consistent irq usage for each lock - * so even though there cannot be a race this early in - * the boot sequence, we still disable irqs. - */ - local_irq_save(flags); add_partial(n, page, 0); - local_irq_restore(flags); } static void free_kmem_cache_nodes(struct kmem_cache *s) @@ -2654,6 +2899,12 @@ static int kmem_cache_open(struct kmem_cache *s, } } +#ifdef CONFIG_CMPXCHG_DOUBLE + if (system_has_cmpxchg_double() && (s->flags & SLAB_DEBUG_FLAGS) == 0) + /* Enable fast mode */ + s->flags |= __CMPXCHG_DOUBLE; +#endif + /* * The larger the object size is, the more pages we want on the partial * list to avoid pounding the page allocator excessively. @@ -2726,7 +2977,7 @@ static void free_partial(struct kmem_cache *s, struct kmem_cache_node *n) spin_lock_irqsave(&n->list_lock, flags); list_for_each_entry_safe(page, h, &n->partial, lru) { if (!page->inuse) { - __remove_partial(n, page); + remove_partial(n, page); discard_slab(s, page); } else { list_slab_objects(s, page, @@ -3094,14 +3345,8 @@ int kmem_cache_shrink(struct kmem_cache *s) * list_lock. page->inuse here is the upper limit. */ list_for_each_entry_safe(page, t, &n->partial, lru) { - if (!page->inuse && slab_trylock(page)) { - /* - * Must hold slab lock here because slab_free - * may have freed the last object and be - * waiting to release the slab. - */ - __remove_partial(n, page); - slab_unlock(page); + if (!page->inuse) { + remove_partial(n, page); discard_slab(s, page); } else { list_move(&page->lru, @@ -3689,12 +3934,9 @@ static int validate_slab(struct kmem_cache *s, struct page *page, static void validate_slab_slab(struct kmem_cache *s, struct page *page, unsigned long *map) { - if (slab_trylock(page)) { - validate_slab(s, page, map); - slab_unlock(page); - } else - printk(KERN_INFO "SLUB %s: Skipped busy slab 0x%p\n", - s->name, page); + slab_lock(page); + validate_slab(s, page, map); + slab_unlock(page); } static int validate_slab_node(struct kmem_cache *s, @@ -4342,8 +4584,10 @@ static ssize_t sanity_checks_store(struct kmem_cache *s, const char *buf, size_t length) { s->flags &= ~SLAB_DEBUG_FREE; - if (buf[0] == '1') + if (buf[0] == '1') { + s->flags &= ~__CMPXCHG_DOUBLE; s->flags |= SLAB_DEBUG_FREE; + } return length; } SLAB_ATTR(sanity_checks); @@ -4357,8 +4601,10 @@ static ssize_t trace_store(struct kmem_cache *s, const char *buf, size_t length) { s->flags &= ~SLAB_TRACE; - if (buf[0] == '1') + if (buf[0] == '1') { + s->flags &= ~__CMPXCHG_DOUBLE; s->flags |= SLAB_TRACE; + } return length; } SLAB_ATTR(trace); @@ -4375,8 +4621,10 @@ static ssize_t red_zone_store(struct kmem_cache *s, return -EBUSY; s->flags &= ~SLAB_RED_ZONE; - if (buf[0] == '1') + if (buf[0] == '1') { + s->flags &= ~__CMPXCHG_DOUBLE; s->flags |= SLAB_RED_ZONE; + } calculate_sizes(s, -1); return length; } @@ -4394,8 +4642,10 @@ static ssize_t poison_store(struct kmem_cache *s, return -EBUSY; s->flags &= ~SLAB_POISON; - if (buf[0] == '1') + if (buf[0] == '1') { + s->flags &= ~__CMPXCHG_DOUBLE; s->flags |= SLAB_POISON; + } calculate_sizes(s, -1); return length; } @@ -4413,8 +4663,10 @@ static ssize_t store_user_store(struct kmem_cache *s, return -EBUSY; s->flags &= ~SLAB_STORE_USER; - if (buf[0] == '1') + if (buf[0] == '1') { + s->flags &= ~__CMPXCHG_DOUBLE; s->flags |= SLAB_STORE_USER; + } calculate_sizes(s, -1); return length; } @@ -4579,6 +4831,7 @@ STAT_ATTR(FREE_REMOVE_PARTIAL, free_remove_partial); STAT_ATTR(ALLOC_FROM_PARTIAL, alloc_from_partial); STAT_ATTR(ALLOC_SLAB, alloc_slab); STAT_ATTR(ALLOC_REFILL, alloc_refill); +STAT_ATTR(ALLOC_NODE_MISMATCH, alloc_node_mismatch); STAT_ATTR(FREE_SLAB, free_slab); STAT_ATTR(CPUSLAB_FLUSH, cpuslab_flush); STAT_ATTR(DEACTIVATE_FULL, deactivate_full); @@ -4586,7 +4839,10 @@ STAT_ATTR(DEACTIVATE_EMPTY, deactivate_empty); STAT_ATTR(DEACTIVATE_TO_HEAD, deactivate_to_head); STAT_ATTR(DEACTIVATE_TO_TAIL, deactivate_to_tail); STAT_ATTR(DEACTIVATE_REMOTE_FREES, deactivate_remote_frees); +STAT_ATTR(DEACTIVATE_BYPASS, deactivate_bypass); STAT_ATTR(ORDER_FALLBACK, order_fallback); +STAT_ATTR(CMPXCHG_DOUBLE_CPU_FAIL, cmpxchg_double_cpu_fail); +STAT_ATTR(CMPXCHG_DOUBLE_FAIL, cmpxchg_double_fail); #endif static struct attribute *slab_attrs[] = { @@ -4636,6 +4892,7 @@ static struct attribute *slab_attrs[] = { &alloc_from_partial_attr.attr, &alloc_slab_attr.attr, &alloc_refill_attr.attr, + &alloc_node_mismatch_attr.attr, &free_slab_attr.attr, &cpuslab_flush_attr.attr, &deactivate_full_attr.attr, @@ -4643,7 +4900,10 @@ static struct attribute *slab_attrs[] = { &deactivate_to_head_attr.attr, &deactivate_to_tail_attr.attr, &deactivate_remote_frees_attr.attr, + &deactivate_bypass_attr.attr, &order_fallback_attr.attr, + &cmpxchg_double_fail_attr.attr, + &cmpxchg_double_cpu_fail_attr.attr, #endif #ifdef CONFIG_FAILSLAB &failslab_attr.attr, diff --git a/tools/slub/slabinfo.c b/tools/slub/slabinfo.c index 516551c9f172..868cc93f7ac2 100644 --- a/tools/slub/slabinfo.c +++ b/tools/slub/slabinfo.c @@ -2,8 +2,9 @@ * Slabinfo: Tool to get reports about slabs * * (C) 2007 sgi, Christoph Lameter + * (C) 2011 Linux Foundation, Christoph Lameter * - * Compile by: + * Compile with: * * gcc -o slabinfo slabinfo.c */ @@ -39,6 +40,8 @@ struct slabinfo { unsigned long cpuslab_flush, deactivate_full, deactivate_empty; unsigned long deactivate_to_head, deactivate_to_tail; unsigned long deactivate_remote_frees, order_fallback; + unsigned long cmpxchg_double_cpu_fail, cmpxchg_double_fail; + unsigned long alloc_node_mismatch, deactivate_bypass; int numa[MAX_NODES]; int numa_partial[MAX_NODES]; } slabinfo[MAX_SLABS]; @@ -99,7 +102,7 @@ static void fatal(const char *x, ...) static void usage(void) { - printf("slabinfo 5/7/2007. (c) 2007 sgi.\n\n" + printf("slabinfo 4/15/2011. (c) 2007 sgi/(c) 2011 Linux Foundation.\n\n" "slabinfo [-ahnpvtsz] [-d debugopts] [slab-regexp]\n" "-a|--aliases Show aliases\n" "-A|--activity Most active slabs first\n" @@ -293,7 +296,7 @@ int line = 0; static void first_line(void) { if (show_activity) - printf("Name Objects Alloc Free %%Fast Fallb O\n"); + printf("Name Objects Alloc Free %%Fast Fallb O CmpX UL\n"); else printf("Name Objects Objsize Space " "Slabs/Part/Cpu O/S O %%Fr %%Ef Flg\n"); @@ -379,14 +382,14 @@ static void show_tracking(struct slabinfo *s) printf("\n%s: Kernel object allocation\n", s->name); printf("-----------------------------------------------------------------------\n"); if (read_slab_obj(s, "alloc_calls")) - printf(buffer); + printf("%s", buffer); else printf("No Data\n"); printf("\n%s: Kernel object freeing\n", s->name); printf("------------------------------------------------------------------------\n"); if (read_slab_obj(s, "free_calls")) - printf(buffer); + printf("%s", buffer); else printf("No Data\n"); @@ -400,7 +403,7 @@ static void ops(struct slabinfo *s) if (read_slab_obj(s, "ops")) { printf("\n%s: kmem_cache operations\n", s->name); printf("--------------------------------------------\n"); - printf(buffer); + printf("%s", buffer); } else printf("\n%s has no kmem_cache operations\n", s->name); } @@ -462,19 +465,32 @@ static void slab_stats(struct slabinfo *s) if (s->cpuslab_flush) printf("Flushes %8lu\n", s->cpuslab_flush); - if (s->alloc_refill) - printf("Refill %8lu\n", s->alloc_refill); - total = s->deactivate_full + s->deactivate_empty + - s->deactivate_to_head + s->deactivate_to_tail; - - if (total) - printf("Deactivate Full=%lu(%lu%%) Empty=%lu(%lu%%) " - "ToHead=%lu(%lu%%) ToTail=%lu(%lu%%)\n", - s->deactivate_full, (s->deactivate_full * 100) / total, - s->deactivate_empty, (s->deactivate_empty * 100) / total, - s->deactivate_to_head, (s->deactivate_to_head * 100) / total, + s->deactivate_to_head + s->deactivate_to_tail + s->deactivate_bypass; + + if (total) { + printf("\nSlab Deactivation Ocurrences %%\n"); + printf("-------------------------------------------------\n"); + printf("Slab full %7lu %3lu%%\n", + s->deactivate_full, (s->deactivate_full * 100) / total); + printf("Slab empty %7lu %3lu%%\n", + s->deactivate_empty, (s->deactivate_empty * 100) / total); + printf("Moved to head of partial list %7lu %3lu%%\n", + s->deactivate_to_head, (s->deactivate_to_head * 100) / total); + printf("Moved to tail of partial list %7lu %3lu%%\n", s->deactivate_to_tail, (s->deactivate_to_tail * 100) / total); + printf("Deactivation bypass %7lu %3lu%%\n", + s->deactivate_bypass, (s->deactivate_bypass * 100) / total); + printf("Refilled from foreign frees %7lu %3lu%%\n", + s->alloc_refill, (s->alloc_refill * 100) / total); + printf("Node mismatch %7lu %3lu%%\n", + s->alloc_node_mismatch, (s->alloc_node_mismatch * 100) / total); + } + + if (s->cmpxchg_double_fail || s->cmpxchg_double_cpu_fail) + printf("\nCmpxchg_double Looping\n------------------------\n"); + printf("Locked Cmpxchg Double redos %lu\nUnlocked Cmpxchg Double redos %lu\n", + s->cmpxchg_double_fail, s->cmpxchg_double_cpu_fail); } static void report(struct slabinfo *s) @@ -573,12 +589,13 @@ static void slabcache(struct slabinfo *s) total_alloc = s->alloc_fastpath + s->alloc_slowpath; total_free = s->free_fastpath + s->free_slowpath; - printf("%-21s %8ld %10ld %10ld %3ld %3ld %5ld %1d\n", + printf("%-21s %8ld %10ld %10ld %3ld %3ld %5ld %1d %4ld %4ld\n", s->name, s->objects, total_alloc, total_free, total_alloc ? (s->alloc_fastpath * 100 / total_alloc) : 0, total_free ? (s->free_fastpath * 100 / total_free) : 0, - s->order_fallback, s->order); + s->order_fallback, s->order, s->cmpxchg_double_fail, + s->cmpxchg_double_cpu_fail); } else printf("%-21s %8ld %7d %8s %14s %4d %1d %3ld %3ld %s\n", @@ -1190,6 +1207,10 @@ static void read_slab_dir(void) slab->deactivate_to_tail = get_obj("deactivate_to_tail"); slab->deactivate_remote_frees = get_obj("deactivate_remote_frees"); slab->order_fallback = get_obj("order_fallback"); + slab->cmpxchg_double_cpu_fail = get_obj("cmpxchg_double_cpu_fail"); + slab->cmpxchg_double_fail = get_obj("cmpxchg_double_fail"); + slab->alloc_node_mismatch = get_obj("alloc_node_mismatch"); + slab->deactivate_bypass = get_obj("deactivate_bypass"); chdir(".."); if (slab->name[0] == ':') alias_targets++; |