linux-kernel - Re: [PATCH -mm] vmscan: make mapped executable pages the first class citizen

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Date:	Tue, 12 May 2009 12:35:22 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"hannes@...xchg.org" <hannes@...xchg.org>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"riel@...hat.com" <riel@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"tytso@....edu" <tytso@....edu>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"elladan@...imo.com" <elladan@...imo.com>,
	"npiggin@...e.de" <npiggin@...e.de>,
	"cl@...ux-foundation.org" <cl@...ux-foundation.org>,
	"kosaki.motohiro@...fujitsu.com" <kosaki.motohiro@...fujitsu.com>,
	"minchan.kim@...il.com" <minchan.kim@...il.com>
Subject: Re: [PATCH -mm] vmscan: make mapped executable pages the first
	class citizen

On Tue, May 12, 2009 at 10:50:58AM +0800, Wu Fengguang wrote:
> > Now.  How do we know that this patch improves Linux?
> 
> Hmm, it seems hard to get measurable performance numbers.
> 
> But we know that the running executable code is precious and shall be
> protected, and the patch protects them in this way:
> 
>         before patch: will be reclaimed if not referenced in I
>         after  patch: will be reclaimed if not referenced in I+A

s/will/may/, to be more exact.

> where
>         A = time to fully scan the active   file LRU
>         I = time to fully scan the inactive file LRU
> 
> Note that normally A >> I.
> 
> Therefore this patch greatly prolongs the in-cache time of executable code,
> when there are moderate memory pressures.

Thanks,
Fengguang

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