Subject: Re: why swap at all?
From: FabF <fabian.frederick@skynet.be>
To: Con Kolivas <kernel@kolivas.org>
Cc: Bernd Eckenfels <ecki-news2004-05@lina.inka.de>,
       linux-kernel@vger.kernel.org
In-Reply-To: <200406022142.52854.kernel@kolivas.org>
References: <E1BVIVG-0003wL-00@calista.eckenfels.6bone.ka-ip.net>
	 <1086154721.2275.2.camel@localhost.localdomain>
	 <200406022142.52854.kernel@kolivas.org>
Content-Type: text/plain
Message-Id: <1086196003.2047.7.camel@localhost.localdomain>
Mime-Version: 1.0
Date: Wed, 02 Jun 2004 19:06:44 +0200
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 3315
Lines: 69

On Wed, 2004-06-02 at 13:42, Con Kolivas wrote:
> On Wed, 2 Jun 2004 15:38, FabF wrote:
> > On Wed, 2004-06-02 at 01:17, Bernd Eckenfels wrote:
> > > In article <200406012000.i51K0vor019011@turing-police.cc.vt.edu> you 
> wrote:
> > > > out (unlike some, I don't mind if Mozilla or OpenOffice end up out on
> > > > disk after extended inactivity - but if my window manager gets swapped
> > > > out, I get peeved when focus-follows-mouse doesn't and my typing goes
> > > > into the wrong window or some such... ;)
> > >
> > > Yes but: your wm is so  often used/activated it will not get swaped  out.
> > > But if your mouse passes over mozilla and tries to focus it, then you
> > > will feel the pain of a swapped-out x program.
> >
> > Exactly !
> > Does autoregulated VM swap. patch could help here ?
> 
> Unless you are pushing the limits of your available ram by your usage pattern 
> then yes the autoregulated swappiness patch should help.
> 
> available here:
> http://ck.kolivas.org/patches/2.6/2.6.7-rc2/patch-2.6.7-rc2-am11
> 
> Just a brief word that might clarify things for people. It seems this huge 
> swap discussion centres around 2 different arguments. Akpm has said that the 
> correct way for the vm to behave is that of swappiness=100. Desktop users 
> note they have less swap out of the programs they use with swappiness 0 or 
> their swap turned off. When your swappiness is set high, the current vm 
> decisions are the fastest they can be, but when you go back to your 
> applications they will take longer to restart. When your swappiness is set 
> low your applications will restart rapidly, but the current vm will be doing 
> more work and be slower. Most benchmarks will show the latter, but most 
> desktop users will feel the former and not really notice the latter.
> 
> Try the little experiment to see: Boot with mem=128M and try to compile a 2.6 
> kernel with all the debugging symbols option enabled - do this with 
> swappiness set to 0 and then at 100. You'll see it compile much faster at 
> 100. Yet you know that if you set your swappiness to 0 mozilla will load 
> faster next time you use it on your desktop during your normal usage pattern 
> (of course you'd probably be using mozilla on a system with a bit more than 
> 128M ram but this helps demonstrate the point). 
> 
> Does this explain in coarse examples to the desktop users why ideal systems 
> shouldn't be swap disabled or swappiness=0 ?
> 
> The autoregulated swappiness patch tries to get some sort of common ground, 
> where it sacrifices performance slightly currently to improve what happens 
> the next time you use your machine substantially. Because it changes with the 
> amount of application pages in ram, it will not increasingly sacrifice 
> performance when your memory is full with application pages. What it will not 
> do is improve the swap thrash situation when you have grossly overloaded your 
> ram.
> 
> Con

My box rocks with you patch Con ! Swappiness is floating between 50->65.
I never saw a 2.6 box so quick in rl5.

Thanks !
FabF


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/