Messages in this thread | | | Date | Mon, 30 Jul 2012 14:12:39 -0500 (CDT) | From | Christoph Lameter <> | Subject | Re: [PATCH] slub: remove one code path and reduce lock contention in __slab_free() |
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On Sat, 28 Jul 2012, JoonSoo Kim wrote:
> 2012/7/28 Christoph Lameter <cl@linux.com>: > > On Sat, 28 Jul 2012, Joonsoo Kim wrote: > > > >> Subject and commit log are changed from v1. > > > > That looks a bit better. But the changelog could use more cleanup and > > clearer expression. > > > >> @@ -2490,25 +2492,17 @@ static void __slab_free(struct kmem_cache *s, struct page *page, > >> return; > >> } > >> > >> + if (unlikely(!new.inuse && n->nr_partial > s->min_partial)) > >> + goto slab_empty; > >> + > > > > So we can never encounter a empty slab that was frozen before? Really? > > In my suggestion, 'was_frozen = 1' is "always" handled without taking a lock.
Yepo that is true with this patch.
> Then, never hit following code. > + if (unlikely(!new.inuse && n->nr_partial > s->min_partial)) > + goto slab_empty; > +
Correct.
> Instead, hit following code. > if (likely(!n)) { > > /* > * If we just froze the page then put it onto the > * per cpu partial list. > */ > if (new.frozen && !was_frozen) { > put_cpu_partial(s, page, 1); > stat(s, CPU_PARTIAL_FREE); > } > /* > * The list lock was not taken therefore no list > * activity can be necessary. > */ > if (was_frozen) > stat(s, FREE_FROZEN); > return; > } > > So, even if we encounter a empty slab that was frozen before, we just > do "stat(s, FREE_FROZEN)". > Please let me know my answer is sufficient.
Yes.
Acked-by: Christoph Lameter <cl@linux.com>
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