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mm/slub: directly load freelist from cpu partial slab in the likely case

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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>
This commit is contained in:
Chengming Zhou 2024-01-23 09:33:29 +00:00 committed by Vlastimil Babka
parent 6613476e22
commit 90b1e56641
1 changed files with 11 additions and 10 deletions
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21
mm/slub.c
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@ -3326,7 +3326,6 @@ 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;
@ -3498,18 +3497,20 @@ new_slab:
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