From: Chengming Zhou zhouchengming@bytedance.com
mainline inclusion from mainline-v6.9-rc1 commit 90b1e56641bbab801e22141c56aa79dc095a3764 category: performance bugzilla: https://gitee.com/openeuler/kernel/issues/I9CSFJ CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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The likely case is that we get a usable slab from the cpu partial list, we can directly load freelist from it and return back, instead of going the other way that need more work, like reenable interrupt and recheck.
But we need to remove the "VM_BUG_ON(!new.frozen)" in get_freelist() for reusing it, since cpu partial slab is not frozen. It seems acceptable since it's only for debug purpose.
And get_freelist() also assumes it can return NULL if the freelist is empty, which is not possible for the cpu partial slab case, so we add "VM_BUG_ON(!freelist)" after get_freelist() to make it explicit.
There is some small performance improvement too, which shows by: perf bench sched messaging -g 5 -t -l 100000
mm-stable slub-optimize Total time 7.473 7.209
Signed-off-by: Chengming Zhou zhouchengming@bytedance.com Reviewed-by: Vlastimil Babka vbabka@suse.cz Signed-off-by: Vlastimil Babka vbabka@suse.cz Signed-off-by: ZhangPeng zhangpeng362@huawei.com --- mm/slub.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-)
diff --git a/mm/slub.c b/mm/slub.c index 211db507a321..07509c40a637 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -3004,7 +3004,6 @@ static inline void *get_freelist(struct kmem_cache *s, struct slab *slab) counters = slab->counters;
new.counters = counters; - VM_BUG_ON(!new.frozen);
new.inuse = slab->objects; new.frozen = freelist != NULL; @@ -3176,18 +3175,20 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
slab = slub_percpu_partial(c); slub_set_percpu_partial(c, slab); - local_unlock_irqrestore(&s->cpu_slab->lock, flags); - stat(s, CPU_PARTIAL_ALLOC);
- if (unlikely(!node_match(slab, node) || - !pfmemalloc_match(slab, gfpflags))) { - slab->next = NULL; - __put_partials(s, slab); - continue; + if (likely(node_match(slab, node) && + pfmemalloc_match(slab, gfpflags))) { + c->slab = slab; + freelist = get_freelist(s, slab); + VM_BUG_ON(!freelist); + stat(s, CPU_PARTIAL_ALLOC); + goto load_freelist; }
- freelist = freeze_slab(s, slab); - goto retry_load_slab; + local_unlock_irqrestore(&s->cpu_slab->lock, flags); + + slab->next = NULL; + __put_partials(s, slab); } #endif