From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263025AbTE0DWt (ORCPT ); Mon, 26 May 2003 23:22:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263056AbTE0DWt (ORCPT ); Mon, 26 May 2003 23:22:49 -0400 Received: from c17870.thoms1.vic.optusnet.com.au ([210.49.248.224]:3230 "EHLO mail.kolivas.org") by vger.kernel.org with ESMTP id S263025AbTE0DWq (ORCPT ); Mon, 26 May 2003 23:22:46 -0400 From: Con Kolivas To: Rodrigo Souza de Castro Subject: Re: [2.4.20-ck7] good compressed caching experience Date: Tue, 27 May 2003 13:37:20 +1000 User-Agent: KMail/1.5.1 Cc: Kimmo Sundqvist , linux-kernel@vger.kernel.org, linuxcompressed-devel@lists.sourceforge.net References: <200305262150.04552.rabbit80@mbnet.fi> <200305270711.34608.kernel@kolivas.org> <20030527014124.GE3388@bach> In-Reply-To: <20030527014124.GE3388@bach> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200305271337.20465.kernel@kolivas.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 27 May 2003 11:41, Rodrigo Souza de Castro wrote: > Hi Con, > > On Tue, May 27, 2003 at 07:11:34AM +1000, Con Kolivas wrote: > > On Tue, 27 May 2003 04:50, Kimmo Sundqvist wrote: > > > I just decided to tell everyone that I've been able to run 2.4.20-ck7 > > > with compressed caching enabled in my little brother's Pentium 133MHz, > > > for hours, doing stress testing, compiling kernels and using the > > > Internet under X. > > > > > > I had pre-empt enabled. Compressed swap worked also. I used 4kB pages > > > without compressed swap, and 8kB with it. > > [snip] > > > > exclusive), 1GB of RAM but "mem=128M" for testing purposes. Been > > > stable for 6 hours now, and done even some stress testing. Try 128 > > > instances of burnBX with 1MB each, like "for ((A=128;A--;A<1)) do > > > burnBX J & done". A nice brute force or "if you don't behave I'll push > > > all my buttons" method > > > > > > :) > > > > > > Wondering if Pentium 133MHz (64MB RAM) is fast enough to benefit from > > > compressed caching. I know there's a limit, depending on the speed of > > > the CPU and the speed of the swap partition (doing random accesses), > > > which determines if compressed caching is beneficial or not. > > [snip] > > > What you describe has been my experience with cc as well. I haven't > > had any crashes or unusual problems with it since removing the AA vm > > changes as well - it seemed to be the combination that caused > > hiccups on extreme testing. > > Something to be figured out yet. It is a pity we couldn't work harder > on these problems. I think getting the stability necessary on the main tree was far more important so I don't regret this. > > > >From what I can see, no matter how slow your cpu you will still get > > > > benefit from cc as the hard drives on those machines are > > proportionately slower as well. > > I guess that, in the past, the gap was smaller, but still there. > > > The one limitation of cc is that it does require _some_ ram to > > actually store swap pages in, and it seems that you need more than > > 32Mb ram to start deriving benefit. > > I am not sure. It requires some ram, but it is only a few pages to > avoid failed page allocations when it first needs to allocate pages. I > have a report of running CC on a laptop with 8M RAM, that showed to be > a little more responsive. I don't have a scientific results showing > that is better on system with a lower amount of memory, but this > feedback seems positive. > > > One minor thing, though - my vm hacks make compressed caching work > > much less than it normally does as they try to avoid swapping quite > > aggressively. It is when the vm attempts to start swapping that cc > > looks to see if it should take pages into compressed cache instead. > > What exactly are your VM hacks concerning CC? The default behaviour is > to compress pages only when the VM starts freeing pages, not in a > compress-ahead fashion, pretty much what I think you said above. Ok, I didn't look at your code, but that would make sense too because with my hacks it will start even lower priority than the default VM freeing less pages at a time unless the memory pressure gets high. > > > I've cc'ed the actual developer of cc as he has indicated that he is > > actively working on compressed caching again. > > At a slower pace, but finally back to CC development. :-) Excellent. Good to have you back. > > > > Just a warning... both systems have only ReiserFS partitions. > > > Other FSes might still get hurt. > > > > This is definitely the case! If you try out compressed caching with > > ck7 please do not enable preempt if you are using ext2/3 or vfat. > > As told in a previous email, I wouldn't enable preempt in any case > with this code version. -ck has always come with a warning saying as much. I hope to integrate more of your code when you're happy with it, so this problem can be resolved. Cheers, Con