From: "Daniel P. Berrange" <berrange@redhat.com>
To: Glauber Costa <glommer@parallels.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
linux-mm@kvack.org, devel@openvz.org,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Michal Hocko <mhocko@suse.cz>,
Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Mel Gorman <mgorman@suse.de>
Subject: Re: [RFC 2/4] memcg: make it suck faster
Date: Wed, 26 Sep 2012 10:03:43 +0100 [thread overview]
Message-ID: <20120926090343.GB31968@redhat.com> (raw)
In-Reply-To: <5062C281.4080805@parallels.com>
On Wed, Sep 26, 2012 at 12:53:21PM +0400, Glauber Costa wrote:
> On 09/26/2012 01:02 AM, Andrew Morton wrote:
> >> nomemcg : memcg compile disabled.
> >> > base : memcg enabled, patch not applied.
> >> > bypassed : memcg enabled, with patch applied.
> >> >
> >> > base bypassed
> >> > User 109.12 105.64
> >> > System 1646.84 1597.98
> >> > Elapsed 229.56 215.76
> >> >
> >> > nomemcg bypassed
> >> > User 104.35 105.64
> >> > System 1578.19 1597.98
> >> > Elapsed 212.33 215.76
> >> >
> >> > So as one can see, the difference between base and nomemcg in terms
> >> > of both system time and elapsed time is quite drastic, and consistent
> >> > with the figures shown by Mel Gorman in the Kernel summit. This is a
> >> > ~ 7 % drop in performance, just by having memcg enabled. memcg functions
> >> > appear heavily in the profiles, even if all tasks lives in the root
> >> > memcg.
> >> >
> >> > With bypassed kernel, we drop this down to 1.5 %, which starts to fall
> >> > in the acceptable range. More investigation is needed to see if we can
> >> > claim that last percent back, but I believe at last part of it should
> >> > be.
> > Well that's encouraging. I wonder how many users will actually benefit
> > from this - did I hear that major distros are now using memcg in some
> > system-infrastructure-style code?
> >
>
> If they do, they actually be come "users of memcg". This here is aimed
> at non-users of memcg, which given all the whining about it, it seems to
> be plenty.
>
> Also, I noticed, for instance, that libvirt is now creating memcg
> hierarchies for lxc and qemu as placeholders, before you actually create
> any vm or container.
This is mostly just lazyness on our part. There's no technical reason
why we can't delay creating our intermediate cgroups until we actually
have a VM ready to start, it was just simpler to create them when we
started the main daemon.
Daniel
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next prev parent reply other threads:[~2012-09-26 9:04 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-25 8:52 [RFC 0/4] bypass charges if memcg is not used Glauber Costa
2012-09-25 8:52 ` [RFC 1/4] memcg: provide root figures from system totals Glauber Costa
2012-10-01 17:00 ` Michal Hocko
2012-10-02 9:15 ` Glauber Costa
2012-10-02 9:34 ` Michal Hocko
2012-09-25 8:52 ` [RFC 2/4] memcg: make it suck faster Glauber Costa
2012-09-25 21:02 ` Andrew Morton
2012-09-26 8:53 ` Glauber Costa
2012-09-26 9:03 ` Daniel P. Berrange [this message]
2012-09-25 8:52 ` [RFC 3/4] memcg: do not call page_cgroup_init at system_boot Glauber Costa
2012-09-25 8:52 ` [RFC 4/4] memcg: do not walk all the way to the root for memcg Glauber Costa
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