linux-kernel - Re: [PATCH 2/2] vmscan: activate executable pages after first usage

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Date:	Tue, 9 Aug 2011 09:04:55 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	Konstantin Khlebnikov <khlebnikov@...nvz.org>, linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Wu Fengguang <fengguang.wu@...el.com>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH 2/2] vmscan: activate executable pages after first usage

On Tue, 9 Aug 2011 09:02:28 +0900
Minchan Kim <minchan.kim@...il.com> wrote:

> On Mon, Aug 8, 2011 at 8:07 PM, Konstantin Khlebnikov
> <khlebnikov@...nvz.org> wrote:
> > Logic added in commit v2.6.30-5507-g8cab475
> > (vmscan: make mapped executable pages the first class citizen)
> > was noticeably weakened in commit v2.6.33-5448-g6457474
> > (vmscan: detect mapped file pages used only once)
> >
> > Currently these pages can become "first class citizens" only after second usage.
> >
> > After this patch page_check_references() will activate they after first usage,
> > and executable code gets yet better chance to stay in memory.
> >
> > TODO:
> > run some cool tests like in v2.6.30-5507-g8cab475 =)
> >
> > Signed-off-by: Konstantin Khlebnikov <khlebnikov@...nvz.org>
> > ---
> 
> It might be a very controversial topic.
> AFAIR, at least, we did when vmscan: make mapped executable pages the
> first class citizen was merged. :)
> 
> You try to change behavior.
> 
> Old : protect *working set* executable page
> New: protect executable page *unconditionally*.
> 

Hmm ? I thought 
Old: protect pages if referenced twice
New: protect executable page if referenced once.

IIUC, ANON is proteced if it's referenced once.

So, this patch changes EXECUTABLE file to the same class as ANON pages.

Anyway, I agree test/measurement is required.

Thanks,
-Kame









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