linux-kernel - Re: [PATCH -mm 3/3] slub: make dead caches discard free slabs immediately

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Message-ID: <CAAmzW4N+HVEO7_29QpzW9ezask4FZYVVUdm0eMKv4CdUwLWYxQ@mail.gmail.com>
Date:	Tue, 27 Jan 2015 18:21:14 +0900
From:	Joonsoo Kim <js1304@...il.com>
To:	Vladimir Davydov <vdavydov@...allels.com>
Cc:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...nel.org>,
	David Rientjes <rientjes@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	Linux Memory Management List <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -mm 3/3] slub: make dead caches discard free slabs immediately

2015-01-27 17:23 GMT+09:00 Vladimir Davydov <vdavydov@...allels.com>:
> Hi Joonsoo,
>
> On Tue, Jan 27, 2015 at 05:00:09PM +0900, Joonsoo Kim wrote:
>> On Mon, Jan 26, 2015 at 03:55:29PM +0300, Vladimir Davydov wrote:
>> > @@ -3381,6 +3390,15 @@ void __kmem_cache_shrink(struct kmem_cache *s)
>> >             kmalloc(sizeof(struct list_head) * objects, GFP_KERNEL);
>> >     unsigned long flags;
>> >
>> > +   if (deactivate) {
>> > +           /*
>> > +            * Disable empty slabs caching. Used to avoid pinning offline
>> > +            * memory cgroups by freeable kmem pages.
>> > +            */
>> > +           s->cpu_partial = 0;
>> > +           s->min_partial = 0;
>> > +   }
>> > +
>>
>> Maybe, kick_all_cpus_sync() is needed here since object would
>> be freed asynchronously so they can't see this updated value.
>
> I thought flush_all() should do the trick, no?

Unfortunately, it doesn't.

flush_all() sends IPI to not all cpus. It only sends IPI to cpus where
some conditions
are met and freeing could occur on the other ones.

Thanks.
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