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

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Date:	Tue, 02 Sep 2014 13:18:55 -0700
From:	Dave Hansen <dave.hansen@...el.com>
To:	Dave Hansen <dave@...1.net>, Johannes Weiner <hannes@...xchg.org>,
	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 12:05 PM, Dave Hansen wrote:
> It does not revert cleanly because of the hunks below.  The code in
> those hunks was removed, so I tried running without properly merging
> them and it spews warnings because counter->usage is seen going negative.
> 
> So, it doesn't appear we can quickly revert this.

I'm fairly confident that I missed some of the cases (especially in the
charge-moving code), but the attached patch does at least work around
the regression for me.  It restores the original performance, or at
least gets _close_ to it.



View attachment "try-partial-revert-of-root-charge-regression-patch.patch" of type "text/x-patch" (1516 bytes)