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: <20140624074853.GB18121@esperanza>
Date:	Tue, 24 Jun 2014 11:48:53 +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

On Tue, Jun 24, 2014 at 04:38:41PM +0900, Joonsoo Kim wrote:
> On Fri, Jun 13, 2014 at 12:38:22AM +0400, Vladimir Davydov wrote:
> > @@ -3462,6 +3474,17 @@ static inline void __cache_free(struct kmem_cache *cachep, void *objp,
> >  
> >  	kmemcheck_slab_free(cachep, objp, cachep->object_size);
> >  
> > +#ifdef CONFIG_MEMCG_KMEM
> > +	if (unlikely(!ac)) {
> > +		int nodeid = page_to_nid(virt_to_page(objp));
> > +
> > +		spin_lock(&cachep->node[nodeid]->list_lock);
> > +		free_block(cachep, &objp, 1, nodeid);
> > +		spin_unlock(&cachep->node[nodeid]->list_lock);
> > +		return;
> > +	}
> > +#endif
> > +
> 
> And, please document intention of this code. :)

Sure.

> And, you said that this way of implementation would be slow because
> there could be many object in dead caches and this implementation
> needs node spin_lock on each object freeing. Is it no problem now?

It may be :(

> If you have any performance data about this implementation and
> alternative one, could you share it?

I haven't (shame on me!). I'll do some testing today and send you the
results.

Thanks.
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