linux-kernel - Re: inux-next: Tree for Apr 27 (uml + mm/memcontrol.c)

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Message-ID: <CABEgKgrkQ=asB2WExQb1KTd1MyoWDwJCO2_u2cJC4toEUa3C4g@mail.gmail.com>
Date:	Fri, 4 May 2012 08:21:31 +0900
From:	Hiroyuki Kamezawa <kamezawa.hiroyuki@...il.com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Randy Dunlap <rdunlap@...otime.net>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-next@...r.kernel.org, linux-kernel@...r.kernel.org,
	Richard Weinberger <richard@....at>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: inux-next: Tree for Apr 27 (uml + mm/memcontrol.c)

On Fri, May 4, 2012 at 6:57 AM, David Rientjes <rientjes@...gle.com> wrote:
> On Thu, 3 May 2012, David Rientjes wrote:
>
>> Is this a claim that memory-intensive workloads will have the exact same
>> performance with and without memcg enabled?
>
> I've just run specjbb2005 three times on my system both with and without
> cgroup_disable=memory on the command line and it is consistently 1% faster
> without memcg.
Hm, ok. Where is that overheads from ? Do you have perf output ?
I'll need to check what is bad.

> If I add XX:+UseLargePages to the command line to use
> hugepages it's even larger.  So why must I incur this performance
> degradation if I simply want to control who may mmap hugepages out of the
> global pool?

Is that common use case ? If he wants to do some resource control,
common users will limit usual memory, too. That kinds of too much flexibility
makes cgroup complicated, hard-to-use.

Thanks,
-Kame
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