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

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Message-Id: <1241709466.11251.164.camel@twins>
Date:	Thu, 07 May 2009 17:17:46 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Johannes Weiner <hannes@...xchg.org>
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>,
	Christoph Lameter <cl@...ux-foundation.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 17:10 +0200, Johannes Weiner wrote:

> > @@ -1269,8 +1270,15 @@ static void shrink_active_list(unsigned 
> >  
> >  		/* page_referenced clears PageReferenced */
> >  		if (page_mapping_inuse(page) &&
> > -		    page_referenced(page, 0, sc->mem_cgroup))
> > +		    page_referenced(page, 0, sc->mem_cgroup)) {
> > +			struct address_space *mapping = page_mapping(page);
> > +
> >  			pgmoved++;
> > +			if (mapping && test_bit(AS_EXEC, &mapping->flags)) {
> > +				list_add(&page->lru, &l_active);
> > +				continue;
> > +			}
> > +		}
> 
> Since we walk the VMAs in page_referenced anyway, wouldn't it be
> better to check if one of them is executable?  This would even work
> for executable anon pages.  After all, there are applications that cow
> executable mappings (sbcl and other language environments that use an
> executable, run-time modified core image come to mind).

Hmm, like provide a vm_flags mask along to page_referenced() to only
account matching vmas... seems like a sensible idea.

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