linux-kernel - Re: [PATCH v4 0/8] Avoid cache trashing on clearing huge/gigantic page

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Message-ID: <20120925142703.GA1598@otc-wbsnb-06>
Date:	Tue, 25 Sep 2012 17:27:03 +0300
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Andi Kleen <ak@...ux.intel.com>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Alex Shi <alex.shu@...el.com>,
	Jan Beulich <jbeulich@...ell.com>,
	Robert Richter <robert.richter@....com>,
	Andy Lutomirski <luto@...capital.net>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Hugh Dickins <hughd@...gle.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Mel Gorman <mgorman@...e.de>, linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-mips@...ux-mips.org,
	linux-sh@...r.kernel.org, sparclinux@...r.kernel.org
Subject: Re: [PATCH v4 0/8] Avoid cache trashing on clearing huge/gigantic
 page

On Fri, Sep 14, 2012 at 07:52:10AM +0200, Ingo Molnar wrote:
> Without repeatable hard numbers such code just gets into the 
> kernel and bitrots there as new CPU generations come in - a few 
> years down the line the original decisions often degrade to pure 
> noise. We've been there, we've done that, we don't want to 
> repeat it.

<sorry, for late answer..>

Hard numbers are hard.
I've checked some workloads: Mosbench, NPB, specjvm2008. Most of time the
patchset doesn't show any difference (within run-to-run deviation).
On NPB it recovers THP regression, but it's probably not enough to make
decision.

It would be nice if somebody test the patchset on other system or
workload. Especially, if the configuration shows regression with
THP enabled.

-- 
 Kirill A. Shutemov

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