linux-kernel - Re: [PATCH 2/3] vmscan: make mapped executable pages the first class citizen

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Message-Id: <1242719063.26820.457.camel@twins>
Date:	Tue, 19 May 2009 09:44:23 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Pekka Enberg <penberg@...helsinki.fi>
Cc:	Wu Fengguang <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Elladan <elladan@...imo.com>, Nick Piggin <npiggin@...e.de>,
	Johannes Weiner <hannes@...xchg.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>,
	"tytso@....edu" <tytso@....edu>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"minchan.kim@...il.com" <minchan.kim@...il.com>
Subject: Re: [PATCH 2/3] vmscan: make mapped executable pages the first
 class  citizen

On Tue, 2009-05-19 at 09:39 +0300, Pekka Enberg wrote:
> Hi!
> 
> On Sat, May 16, 2009 at 12:00 PM, Wu Fengguang <fengguang.wu@...el.com> wrote:
> > @@ -1272,28 +1273,40 @@ static void shrink_active_list(unsigned
> >
> >                /* page_referenced clears PageReferenced */
> >                if (page_mapping_inuse(page) &&
> > -                   page_referenced(page, 0, sc->mem_cgroup, &vm_flags))
> > +                   page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
> >                        pgmoved++;
> > +                       /*
> > +                        * Identify referenced, file-backed active pages and
> > +                        * give them one more trip around the active list. So
> > +                        * that executable code get better chances to stay in
> > +                        * memory under moderate memory pressure.  Anon pages
> > +                        * are ignored, since JVM can create lots of anon
> > +                        * VM_EXEC pages.
> > +                        */
> > +                       if ((vm_flags & VM_EXEC) && !PageAnon(page)) {
> > +                               list_add(&page->lru, &l_active);
> > +                               continue;
> > +                       }
> 
> Why do we need to skip JIT'd code? There are plenty of desktop
> applications that use Mono, for example, and it would be nice if we
> gave them the same treatment as native applications. Likewise, I am
> sure all browsers that use JIT for JavaScript need to be considered.

Its a sekrit conspiracy against bloat by making JIT'd crap run
slower :-)

<rant>
Anyway, I just checked, we install tons of mono junk for _2_
applications, f-spot and tomboy, both are shite and both have
alternatives not requiring this disease.
</rant>

But seriously, like Kosaka-san already said, anonymous pages are treated
differently from file pages and should not suffer the same problems.
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