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Message-ID: <alpine.DEB.2.00.1001132229250.15428@chino.kir.corp.google.com>
Date: Wed, 13 Jan 2010 22:33:03 -0800 (PST)
From: David Rientjes <rientjes@...gle.com>
To: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
cc: LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
Andrew Morton <akpm@...ux-foundation.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
Minchan Kim <minchan.kim@...il.com>,
Wu Fengguang <fengguang.wu@...el.com>,
Huang Shijie <shijie8@...il.com>
Subject: Re: [resend][PATCH] mm: Restore zone->all_unreclaimable to independence
word
On Thu, 14 Jan 2010, KOSAKI Motohiro wrote:
> commit e815af95 (change all_unreclaimable zone member to flags) chage
> all_unreclaimable member to bit flag. but It have undesireble side
> effect.
> free_one_page() is one of most hot path in linux kernel and increasing
> atomic ops in it can reduce kernel performance a bit.
>
> Thus, this patch revert such commit partially. at least
> all_unreclaimable shouldn't share memory word with other zone flags.
>
I still think you need to quantify this; saying you don't have a large
enough of a machine that will benefit from it isn't really a rationale for
the lack of any data supporting your claim. We should be basing VM
changes on data, not on speculation that there's a measurable impact
here.
Perhaps you could ask a colleague or another hacker to run a benchmark for
you so that the changelog is complete?
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