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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Pekka Enberg <penberg@cs.helsinki.fi>
Subject: Re: [PATCH 2/3] vmscan: make mapped executable pages the first class  citizen
Cc: kosaki.motohiro@jp.fujitsu.com, Wu Fengguang <fengguang.wu@intel.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       LKML <linux-kernel@vger.kernel.org>, Elladan <elladan@eskimo.com>,
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Date: Tue, 19 May 2009 15:56:25 +0900 (JST)
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Hi

> 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.

anon pages are already protected from streaming-io by get_scan_ratio().