linux-kernel - Re: regression caused by cgroups optimization in 3.17-rc2

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Date:	Tue, 02 Sep 2014 15:36:29 -0700
From:	Dave Hansen <dave@...1.net>
To:	Johannes Weiner <hannes@...xchg.org>
CC:	Michal Hocko <mhocko@...e.com>, Hugh Dickins <hughd@...gle.com>,
	Tejun Heo <tj@...nel.org>,
	Vladimir Davydov <vdavydov@...allels.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>
Subject: Re: regression caused by cgroups optimization in 3.17-rc2

On 09/02/2014 03:18 PM, Johannes Weiner wrote:
> Accounting new pages is buffered through per-cpu caches, but taking
> them off the counters on free is not, so I'm guessing that above a
> certain allocation rate the cost of locking and changing the counters
> takes over.  Is there a chance you could profile this to see if locks
> and res_counter-related operations show up?

It looks pretty much the same, although it might have equalized the
charge and uncharge sides a bit.  Full 'perf top' output attached.

View attachment "perf-20140902-johannes-take1.txt" of type "text/plain" (17406 bytes)