From 8ff12cfc009a2a38d87fa7058226fe197bb2696f Mon Sep 17 00:00:00 2001 From: Christoph Lameter Date: Thu, 7 Feb 2008 17:47:41 -0800 Subject: SLUB: Support for performance statistics The statistics provided here allow the monitoring of allocator behavior but at the cost of some (minimal) loss of performance. Counters are placed in SLUB's per cpu data structure. The per cpu structure may be extended by the statistics to grow larger than one cacheline which will increase the cache footprint of SLUB. There is a compile option to enable/disable the inclusion of the runtime statistics and its off by default. The slabinfo tool is enhanced to support these statistics via two options: -D Switches the line of information displayed for a slab from size mode to activity mode. -A Sorts the slabs displayed by activity. This allows the display of the slabs most important to the performance of a certain load. -r Report option will report detailed statistics on Example (tbench load): slabinfo -AD ->Shows the most active slabs Name Objects Alloc Free %Fast skbuff_fclone_cache 33 111953835 111953835 99 99 :0000192 2666 5283688 5281047 99 99 :0001024 849 5247230 5246389 83 83 vm_area_struct 1349 119642 118355 91 22 :0004096 15 66753 66751 98 98 :0000064 2067 25297 23383 98 78 dentry 10259 28635 18464 91 45 :0000080 11004 18950 8089 98 98 :0000096 1703 12358 10784 99 98 :0000128 762 10582 9875 94 18 :0000512 184 9807 9647 95 81 :0002048 479 9669 9195 83 65 anon_vma 777 9461 9002 99 71 kmalloc-8 6492 9981 5624 99 97 :0000768 258 7174 6931 58 15 So the skbuff_fclone_cache is of highest importance for the tbench load. Pretty high load on the 192 sized slab. Look for the aliases slabinfo -a | grep 000192 :0000192 <- xfs_btree_cur filp kmalloc-192 uid_cache tw_sock_TCP request_sock_TCPv6 tw_sock_TCPv6 skbuff_head_cache xfs_ili Likely skbuff_head_cache. Looking into the statistics of the skbuff_fclone_cache is possible through slabinfo skbuff_fclone_cache ->-r option implied if cache name is mentioned .... Usual output ... Slab Perf Counter Alloc Free %Al %Fr -------------------------------------------------- Fastpath 111953360 111946981 99 99 Slowpath 1044 7423 0 0 Page Alloc 272 264 0 0 Add partial 25 325 0 0 Remove partial 86 264 0 0 RemoteObj/SlabFrozen 350 4832 0 0 Total 111954404 111954404 Flushes 49 Refill 0 Deactivate Full=325(92%) Empty=0(0%) ToHead=24(6%) ToTail=1(0%) Looks good because the fastpath is overwhelmingly taken. skbuff_head_cache: Slab Perf Counter Alloc Free %Al %Fr -------------------------------------------------- Fastpath 5297262 5259882 99 99 Slowpath 4477 39586 0 0 Page Alloc 937 824 0 0 Add partial 0 2515 0 0 Remove partial 1691 824 0 0 RemoteObj/SlabFrozen 2621 9684 0 0 Total 5301739 5299468 Deactivate Full=2620(100%) Empty=0(0%) ToHead=0(0%) ToTail=0(0%) Descriptions of the output: Total: The total number of allocation and frees that occurred for a slab Fastpath: The number of allocations/frees that used the fastpath. Slowpath: Other allocations Page Alloc: Number of calls to the page allocator as a result of slowpath processing Add Partial: Number of slabs added to the partial list through free or alloc (occurs during cpuslab flushes) Remove Partial: Number of slabs removed from the partial list as a result of allocations retrieving a partial slab or by a free freeing the last object of a slab. RemoteObj/Froz: How many times were remotely freed object encountered when a slab was about to be deactivated. Frozen: How many times was free able to skip list processing because the slab was in use as the cpuslab of another processor. Flushes: Number of times the cpuslab was flushed on request (kmem_cache_shrink, may result from races in __slab_alloc) Refill: Number of times we were able to refill the cpuslab from remotely freed objects for the same slab. Deactivate: Statistics how slabs were deactivated. Shows how they were put onto the partial list. In general fastpath is very good. Slowpath without partial list processing is also desirable. Any touching of partial list uses node specific locks which may potentially cause list lock contention. Signed-off-by: Christoph Lameter --- mm/slub.c | 127 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 119 insertions(+), 8 deletions(-) (limited to 'mm') diff --git a/mm/slub.c b/mm/slub.c index 20ab8f0a4eb9..ac836d31e3be 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -250,6 +250,7 @@ enum track_item { TRACK_ALLOC, TRACK_FREE }; static int sysfs_slab_add(struct kmem_cache *); static int sysfs_slab_alias(struct kmem_cache *, const char *); static void sysfs_slab_remove(struct kmem_cache *); + #else static inline int sysfs_slab_add(struct kmem_cache *s) { return 0; } static inline int sysfs_slab_alias(struct kmem_cache *s, const char *p) @@ -258,8 +259,16 @@ static inline void sysfs_slab_remove(struct kmem_cache *s) { kfree(s); } + #endif +static inline void stat(struct kmem_cache_cpu *c, enum stat_item si) +{ +#ifdef CONFIG_SLUB_STATS + c->stat[si]++; +#endif +} + /******************************************************************** * Core slab cache functions *******************************************************************/ @@ -1364,17 +1373,22 @@ static struct page *get_partial(struct kmem_cache *s, gfp_t flags, int node) static void unfreeze_slab(struct kmem_cache *s, struct page *page, int tail) { struct kmem_cache_node *n = get_node(s, page_to_nid(page)); + struct kmem_cache_cpu *c = get_cpu_slab(s, smp_processor_id()); ClearSlabFrozen(page); if (page->inuse) { - if (page->freelist != page->end) + if (page->freelist != page->end) { add_partial(n, page, tail); - else if (SlabDebug(page) && (s->flags & SLAB_STORE_USER)) - add_full(n, page); + stat(c, tail ? DEACTIVATE_TO_TAIL : DEACTIVATE_TO_HEAD); + } else { + stat(c, DEACTIVATE_FULL); + if (SlabDebug(page) && (s->flags & SLAB_STORE_USER)) + add_full(n, page); + } slab_unlock(page); - } else { + stat(c, DEACTIVATE_EMPTY); if (n->nr_partial < MIN_PARTIAL) { /* * Adding an empty slab to the partial slabs in order @@ -1388,6 +1402,7 @@ static void unfreeze_slab(struct kmem_cache *s, struct page *page, int tail) slab_unlock(page); } else { slab_unlock(page); + stat(get_cpu_slab(s, raw_smp_processor_id()), FREE_SLAB); discard_slab(s, page); } } @@ -1400,6 +1415,9 @@ static void deactivate_slab(struct kmem_cache *s, struct kmem_cache_cpu *c) { struct page *page = c->page; int tail = 1; + + if (c->freelist) + stat(c, DEACTIVATE_REMOTE_FREES); /* * Merge cpu freelist into freelist. Typically we get here * because both freelists are empty. So this is unlikely @@ -1429,6 +1447,7 @@ static void deactivate_slab(struct kmem_cache *s, struct kmem_cache_cpu *c) static inline void flush_slab(struct kmem_cache *s, struct kmem_cache_cpu *c) { + stat(c, CPUSLAB_FLUSH); slab_lock(c->page); deactivate_slab(s, c); } @@ -1511,6 +1530,7 @@ static void *__slab_alloc(struct kmem_cache *s, slab_lock(c->page); if (unlikely(!node_match(c, node))) goto another_slab; + stat(c, ALLOC_REFILL); load_freelist: object = c->page->freelist; if (unlikely(object == c->page->end)) @@ -1525,6 +1545,7 @@ load_freelist: c->node = page_to_nid(c->page); unlock_out: slab_unlock(c->page); + stat(c, ALLOC_SLOWPATH); out: #ifdef SLUB_FASTPATH local_irq_restore(flags); @@ -1538,6 +1559,7 @@ new_slab: new = get_partial(s, gfpflags, node); if (new) { c->page = new; + stat(c, ALLOC_FROM_PARTIAL); goto load_freelist; } @@ -1551,6 +1573,7 @@ new_slab: if (new) { c = get_cpu_slab(s, smp_processor_id()); + stat(c, ALLOC_SLAB); if (c->page) flush_slab(s, c); slab_lock(new); @@ -1610,6 +1633,7 @@ static __always_inline void *slab_alloc(struct kmem_cache *s, object = __slab_alloc(s, gfpflags, node, addr, c); break; } + stat(c, ALLOC_FASTPATH); } while (cmpxchg_local(&c->freelist, object, object[c->offset]) != object); #else @@ -1624,6 +1648,7 @@ static __always_inline void *slab_alloc(struct kmem_cache *s, else { object = c->freelist; c->freelist = object[c->offset]; + stat(c, ALLOC_FASTPATH); } local_irq_restore(flags); #endif @@ -1661,12 +1686,15 @@ static void __slab_free(struct kmem_cache *s, struct page *page, { void *prior; void **object = (void *)x; + struct kmem_cache_cpu *c; #ifdef SLUB_FASTPATH unsigned long flags; local_irq_save(flags); #endif + c = get_cpu_slab(s, raw_smp_processor_id()); + stat(c, FREE_SLOWPATH); slab_lock(page); if (unlikely(SlabDebug(page))) @@ -1676,8 +1704,10 @@ checks_ok: page->freelist = object; page->inuse--; - if (unlikely(SlabFrozen(page))) + if (unlikely(SlabFrozen(page))) { + stat(c, FREE_FROZEN); goto out_unlock; + } if (unlikely(!page->inuse)) goto slab_empty; @@ -1687,8 +1717,10 @@ checks_ok: * was not on the partial list before * then add it. */ - if (unlikely(prior == page->end)) + if (unlikely(prior == page->end)) { add_partial(get_node(s, page_to_nid(page)), page, 1); + stat(c, FREE_ADD_PARTIAL); + } out_unlock: slab_unlock(page); @@ -1698,13 +1730,15 @@ out_unlock: return; slab_empty: - if (prior != page->end) + if (prior != page->end) { /* * Slab still on the partial list. */ remove_partial(s, page); - + stat(c, FREE_REMOVE_PARTIAL); + } slab_unlock(page); + stat(c, FREE_SLAB); #ifdef SLUB_FASTPATH local_irq_restore(flags); #endif @@ -1758,6 +1792,7 @@ static __always_inline void slab_free(struct kmem_cache *s, break; } object[c->offset] = freelist; + stat(c, FREE_FASTPATH); } while (cmpxchg_local(&c->freelist, freelist, object) != freelist); #else unsigned long flags; @@ -1768,6 +1803,7 @@ static __always_inline void slab_free(struct kmem_cache *s, if (likely(page == c->page && c->node >= 0)) { object[c->offset] = c->freelist; c->freelist = object; + stat(c, FREE_FASTPATH); } else __slab_free(s, page, x, addr, c->offset); @@ -3980,6 +4016,62 @@ static ssize_t remote_node_defrag_ratio_store(struct kmem_cache *s, SLAB_ATTR(remote_node_defrag_ratio); #endif +#ifdef CONFIG_SLUB_STATS + +static int show_stat(struct kmem_cache *s, char *buf, enum stat_item si) +{ + unsigned long sum = 0; + int cpu; + int len; + int *data = kmalloc(nr_cpu_ids * sizeof(int), GFP_KERNEL); + + if (!data) + return -ENOMEM; + + for_each_online_cpu(cpu) { + unsigned x = get_cpu_slab(s, cpu)->stat[si]; + + data[cpu] = x; + sum += x; + } + + len = sprintf(buf, "%lu", sum); + + for_each_online_cpu(cpu) { + if (data[cpu] && len < PAGE_SIZE - 20) + len += sprintf(buf + len, " c%d=%u", cpu, data[cpu]); + } + kfree(data); + return len + sprintf(buf + len, "\n"); +} + +#define STAT_ATTR(si, text) \ +static ssize_t text##_show(struct kmem_cache *s, char *buf) \ +{ \ + return show_stat(s, buf, si); \ +} \ +SLAB_ATTR_RO(text); \ + +STAT_ATTR(ALLOC_FASTPATH, alloc_fastpath); +STAT_ATTR(ALLOC_SLOWPATH, alloc_slowpath); +STAT_ATTR(FREE_FASTPATH, free_fastpath); +STAT_ATTR(FREE_SLOWPATH, free_slowpath); +STAT_ATTR(FREE_FROZEN, free_frozen); +STAT_ATTR(FREE_ADD_PARTIAL, free_add_partial); +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(FREE_SLAB, free_slab); +STAT_ATTR(CPUSLAB_FLUSH, cpuslab_flush); +STAT_ATTR(DEACTIVATE_FULL, deactivate_full); +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); + +#endif + static struct attribute *slab_attrs[] = { &slab_size_attr.attr, &object_size_attr.attr, @@ -4009,6 +4101,25 @@ static struct attribute *slab_attrs[] = { #endif #ifdef CONFIG_NUMA &remote_node_defrag_ratio_attr.attr, +#endif +#ifdef CONFIG_SLUB_STATS + &alloc_fastpath_attr.attr, + &alloc_slowpath_attr.attr, + &free_fastpath_attr.attr, + &free_slowpath_attr.attr, + &free_frozen_attr.attr, + &free_add_partial_attr.attr, + &free_remove_partial_attr.attr, + &alloc_from_partial_attr.attr, + &alloc_slab_attr.attr, + &alloc_refill_attr.attr, + &free_slab_attr.attr, + &cpuslab_flush_attr.attr, + &deactivate_full_attr.attr, + &deactivate_empty_attr.attr, + &deactivate_to_head_attr.attr, + &deactivate_to_tail_attr.attr, + &deactivate_remote_frees_attr.attr, #endif NULL }; 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