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

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Date:	Tue, 19 May 2009 12:48:32 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	Christoph Lameter <cl@...ux-foundation.org>,
	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>,
	Peter Zijlstra <peterz@...radead.org>,
	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, May 19, 2009 at 12:44:19PM +0800, KOSAKI Motohiro wrote:
> > > begin:       2479             2344             9659              210                0           579643
> > > end:          284           232010           234142              260           772776         20917184
> > > restore:      379           232159           234371              301           774888         20967849
> > > 
> > > The numbers show that
> > > 
> > > - The startup pgmajfault of 2.6.30-rc4-mm is merely 1/3 that of 2.6.29.
> > >   I'd attribute that improvement to the mmap readahead improvements :-)
> > > 
> > > - The pgmajfault increment during the file copy is 633-630=3 vs 260-210=50.
> > >   That's a huge improvement - which means with the VM_EXEC protection logic,
> > >   active mmap pages is pretty safe even under partially cache hot streaming IO.
> > > 
> > > - when active:inactive file lru size reaches 1:1, their scan rates is 1:20.8
> > >   under 10% cache hot IO. (computed with formula Dpgdeactivate:Dpgfree)
> > >   That roughly means the active mmap pages get 20.8 more chances to get
> > >   re-referenced to stay in memory.
> > > 
> > > - The absolute nr_mapped drops considerably to 1/9 during the big IO, and the
> > >   dropped pages are mostly inactive ones. The patch has almost no impact in
> > >   this aspect, that means it won't unnecessarily increase memory pressure.
> > >   (In contrast, your 20% mmap protection ratio will keep them all, and
> > >   therefore eliminate the extra 41 major faults to restore working set
> > >   of zsh etc.)
> > 
> > I'm surprised this.
> > Why your patch don't protect mapped page from streaming io?
> 
> I guess you use initlevel=5 and use only terminal, right?
> if so, dropping some graphics component makes sense.

No, it's in pure console mode, no X running at all.

> 
> > 
> > I strongly hope reproduce myself, please teach me reproduce way.
> 
> 
> 
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