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

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Message-Id: <1241707081.11251.160.camel@twins>
Date:	Thu, 07 May 2009 16:38:01 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Wu Fengguang <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <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 <elladan@...imo.com>, Nick Piggin <npiggin@...e.de>,
	Johannes Weiner <hannes@...xchg.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Subject: Re: [PATCH -mm] vmscan: make mapped executable pages the first
 class citizen

On Thu, 2009-05-07 at 10:18 -0400, Christoph Lameter wrote:
> On Thu, 7 May 2009, Peter Zijlstra wrote:
> 
> > It re-instates the young bit for PROT_EXEC pages, so that they will only
> > be paged when they are really cold, or there is severe pressure.
> 
> But they are rescanned until then. Really cold means what exactly? I do a
> back up of a few hundred gigabytes and do not use firefox while the backup
> is ongoing. Will the firefox pages still be in memory or not?

Likely not.

What this patch does is check the young bit on active_file scan, if its
found to be set and the page is PROT_EXEC, put the page back on the
active_file list, otherwise drop it to the inactive_file list.

So if you haven't ran any firefox code, it should be gone from the
active list after 2 full cycles, and from the inactive list on the first
full inactive cycle after that.

If you don't understand the patch, what are you complaining about, whats
your point?
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