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Subject: Re: [PATCH 2/3] vmscan: make mapped executable pages the first
 class  citizen
From: Peter Zijlstra <peterz@infradead.org>
To: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Wu Fengguang <fengguang.wu@intel.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       LKML <linux-kernel@vger.kernel.org>, Elladan <elladan@eskimo.com>,
       Nick Piggin <npiggin@suse.de>, Johannes Weiner <hannes@cmpxchg.org>,
       Christoph Lameter <cl@linux-foundation.org>,
       KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
       Rik van Riel <riel@redhat.com>, "tytso@mit.edu" <tytso@mit.edu>,
       "linux-mm@kvack.org" <linux-mm@kvack.org>,
       "minchan.kim@gmail.com" <minchan.kim@gmail.com>
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Date: Tue, 19 May 2009 09:44:23 +0200
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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@intel.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.