linux-kernel - Re: [PATCH v3 06/16] memcg: infrastructure to match an allocation to the right cache

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 24 Sep 2012 10:56:19 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Glauber Costa <glommer@...allels.com>
Cc:	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	kamezawa.hiroyu@...fujitsu.com, devel@...nvz.org,
	linux-mm@...ck.org, Suleiman Souhlal <suleiman@...gle.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH v3 06/16] memcg: infrastructure to match an allocation
 to the right cache

Hello, Glauber.

On Mon, Sep 24, 2012 at 12:46:35PM +0400, Glauber Costa wrote:
> >> +#ifdef CONFIG_MEMCG_KMEM
> >> +	/* Slab accounting */
> >> +	struct kmem_cache *slabs[MAX_KMEM_CACHE_TYPES];
> >> +#endif
> > 
> > Bah, 400 entry array in struct mem_cgroup.  Can't we do something a
> > bit more flexible?
> > 
> 
> I guess. I still would like it to be an array, so we can easily access
> its fields. There are two ways around this:
> 
> 1) Do like the events mechanism and allocate this in a separate
> structure. Add a pointer chase in the access, and I don't think it helps
> much because it gets allocated anyway. But we could at least
> defer it to the time when we limit the cache.

Start at some reasonable size and then double it as usage grows?  How
many kmem_caches do we typically end up using?

> >> +	if (memcg->slabs[idx] == NULL) {
> >> +		memcg_create_cache_enqueue(memcg, cachep);
> > 
> > Do we want to wait for the work item if @gfp allows?
> > 
> 
> I tried this once, and it got complicated enough that I deemed as "not
> worth it". I honestly don't remember much of the details now, it was one
> of the first things I tried, and a bunch of time has passed. If you
> think it is absolutely worth it, I can try it again. But at the very
> best, I view this as an optimization.

I don't know.  It seems like a logical thing to try and depends on how
complex it gets.  I don't think it's a must.  The whole thing is
somewhat opportunistic after all.

Thanks.

-- 
tejun
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/