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  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:	Sun, 30 Sep 2012 17:23:58 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Glauber Costa <glommer@...allels.com>
Cc:	Mel Gorman <mgorman@...e.de>, Michal Hocko <mhocko@...e.cz>,
	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>,
	David Rientjes <rientjes@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH v3 04/13] kmem accounting basic infrastructure

Hello, Glauber.

On Thu, Sep 27, 2012 at 10:30:36PM +0400, Glauber Costa wrote:
> > But that happens only when pages enter and leave slab and if it still
> > is significant, we can try to further optimize charging.  Given that
> > this is only for cases where memcg is already in use and we provide a
> > switch to disable it globally, I really don't think this warrants
> > implementing fully hierarchy configuration.
> 
> Not totally true. We still have to match every allocation to the right
> cache, and that is actually our heaviest hit, responsible for the 2, 3 %
> we're seeing when this is enabled. It is the kind of path so hot that
> people frown upon branches being added, so I don't think we'll ever get
> this close to being free.

Sure, depening on workload, any addition to alloc/free could be
noticeable.  I don't know.  I'll write more about it when replying to
Michal's message.  BTW, __memcg_kmem_get_cache() does seem a bit
heavy.  I wonder whether indexing from cache side would make it
cheaper?  e.g. something like the following.

	kmem_cache *__memcg_kmem_get_cache(cachep, gfp)
	{
		struct kmem_cache *c;

		c = cachep->memcg_params->caches[percpu_read(kmemcg_slab_idx)];
		if (likely(c))
			return c;
		/* try to create and then fall back to cachep */
	}

where kmemcg_slab_idx is updated from sched notifier (or maybe add and
use current->kmemcg_slab_idx?).  You would still need __GFP_* and
in_interrupt() tests but current->mm and PF_KTHREAD tests can be
rolled into index selection.

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/

Powered by blists - more mailing lists