linux-kernel - Re: [PATCH -mm v3 8/8] slab: do not keep free objects/slabs on dead memcg caches

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Message-ID: <20140624074258.GA18121@esperanza>
Date:	Tue, 24 Jun 2014 11:42:58 +0400
From:	Vladimir Davydov <vdavydov@...allels.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
CC:	<akpm@...ux-foundation.org>, <cl@...ux.com>, <rientjes@...gle.com>,
	<penberg@...nel.org>, <hannes@...xchg.org>, <mhocko@...e.cz>,
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: [PATCH -mm v3 8/8] slab: do not keep free objects/slabs on dead
 memcg caches

Hi,

On Tue, Jun 24, 2014 at 04:25:54PM +0900, Joonsoo Kim wrote:
> On Fri, Jun 13, 2014 at 12:38:22AM +0400, Vladimir Davydov wrote:
> > @@ -3368,7 +3379,8 @@ static void free_block(struct kmem_cache *cachep, void **objpp, int nr_objects,
> >  
> >  		/* fixup slab chains */
> >  		if (page->active == 0) {
> > -			if (n->free_objects > n->free_limit) {
> > +			if (n->free_objects > n->free_limit ||
> > +			    memcg_cache_dead(cachep)) {
> 
> I'd like to set 0 to free_limit in __kmem_cache_shrink()
> rather than memcg_cache_dead() test here, because memcg_cache_dead()
> is more expensive than it. Is there any problem in this way?

We'd have to be careful on cpu hotplug then, because it may update the
free_limit. Not a big problem though. Will fix.

Thanks.
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