linux-kernel - Re: [PATCH 0/4] Fix ebizzy performance regression due to X86 TLB range flush v2

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Date:	Fri, 20 Dec 2013 11:13:03 +0000
From:	Mel Gorman <mgorman@...e.de>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alex Shi <alex.shi@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Fengguang Wu <fengguang.wu@...el.com>,
	H Peter Anvin <hpa@...or.com>, Linux-X86 <x86@...nel.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 0/4] Fix ebizzy performance regression due to X86 TLB
 range flush v2

On Thu, Dec 19, 2013 at 05:49:25PM +0100, Ingo Molnar wrote:
> 
> * Mel Gorman <mgorman@...e.de> wrote:
> 
> > [...]
> > 
> > Because we lack data on TLB range flush distributions I think we 
> > should still go with the conservative choice for the TLB flush 
> > shift. The worst case is really bad here and it's painfully obvious 
> > on ebizzy.
> 
> So I'm obviously much in favor of this - I'd in fact suggest making 
> the conservative choice on _all_ CPU models that have aggressive TLB 
> range values right now, because frankly the testing used to pick those 
> values does not look all that convincing to me.
> 

I think the choices there are already reasonably conservative. I'd be
reluctant to support merging a patch that made a choice on all CPU models
without having access to the machines to run tests on. I don't see the
Intel people volunteering to do the necessary testing.

-- 
Mel Gorman
SUSE Labs
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