linux-kernel - Re: [PATCH] mm: slub: fix page->

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Message-ID: <alpine.DEB.2.02.1401290029120.12210@chino.kir.corp.google.com>
Date:	Wed, 29 Jan 2014 00:30:19 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Dave Hansen <dave@...1.net>
cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, cl@...ux-foundation.org,
	penberg@...nel.org, mpm@...enic.com, pshelar@...ira.com,
	Wu Fengguang <fengguang.wu@...el.com>
Subject: Re: [PATCH] mm: slub: fix page->_count corruption (again)

On Tue, 28 Jan 2014, Dave Hansen wrote:

> It has measurable performance benefits, and the benefits go up as the
> cost of en/disabling interrupts goes up (like if it takes you a hypercall).
> 
> Fengguang, could you run a set of tests for the top patch in this branch
> to see if we'd be giving much up by axing the code?
> 
> 	https://github.com/hansendc/linux/tree/slub-nocmpxchg-for-Fengguang-20140128
> 
> I was talking with one of the distros about turning it off as well.
> They mentioned that they saw a few performance regressions when it was
> turned off.  I'll share details when I get them.
> 

FWIW, I've compared netperf TCP_RR on all machine types I have available 
with and without cmpxchg_double and I've never measured a regression.
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