linux-kernel - Re: [PATCH 3/9] slab: simplify shutdown_memcg

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Date:   Sat, 14 Jan 2017 10:53:43 -0500
From:   Tejun Heo <tj@...nel.org>
To:     Vladimir Davydov <vdavydov@...antool.org>
Cc:     cl@...ux.com, penberg@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, akpm@...ux-foundation.org, jsvana@...com,
        hannes@...xchg.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, cgroups@...r.kernel.org, kernel-team@...com
Subject: Re: [PATCH 3/9] slab: simplify shutdown_memcg_caches()

On Sat, Jan 14, 2017 at 10:38:01AM -0500, Tejun Heo wrote:
> On Sat, Jan 14, 2017 at 04:27:22PM +0300, Vladimir Davydov wrote:
> > > -	 * Second, shutdown all caches left from memory cgroups that are now
> > > -	 * offline.
> > > +	 * Shutdown all caches.
> > >  	 */
> > >  	list_for_each_entry_safe(c, c2, &s->memcg_params.list,
> > >  				 memcg_params.list)
> > >  		shutdown_cache(c);
> > 
> > The point of this complexity was to leave caches that happen to have
> > objects when kmem_cache_destroy() is called on the list, so that they
> > could be reused later. This behavior was inherited from the global
> 
> Ah, right, I misread the branch.  I don't quite get how the cache can
> be reused later tho?  This is called when the memcg gets released and
> a clear error condition - the caller, kmem_cache_destroy(), handles it
> as an error condition too.

I think I understand it now.  This is the alias being able to find and
reuse the cache.  Heh, that's a weird optimization for a corner error
case.  Anyways, I'll drop this patch.

Thanks.

-- 
tejun