Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262328AbUJ0IVf (ORCPT ); Wed, 27 Oct 2004 04:21:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262327AbUJ0IVe (ORCPT ); Wed, 27 Oct 2004 04:21:34 -0400 Received: from ozlabs.org ([203.10.76.45]:29134 "EHLO ozlabs.org") by vger.kernel.org with ESMTP id S262328AbUJ0IV1 (ORCPT ); Wed, 27 Oct 2004 04:21:27 -0400 Date: Wed, 27 Oct 2004 18:20:03 +1000 From: David Gibson To: Andrew Morton Cc: James Cloos , linux-kernel@vger.kernel.org Subject: Re: MAP_SHARED bizarrely slow Message-ID: <20041027082003.GL1676@zax> Mail-Followup-To: David Gibson , Andrew Morton , James Cloos , linux-kernel@vger.kernel.org References: <20041027064527.GJ1676@zax> <20041027010659.15ec7e90.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20041027010659.15ec7e90.akpm@osdl.org> User-Agent: Mutt/1.5.6+20040907i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3083 Lines: 73 On Wed, Oct 27, 2004 at 01:06:59AM -0700, Andrew Morton wrote: > James Cloos wrote: > > > > >>>>> "David" == David Gibson writes: > > > > David> http://www.ozlabs.org/people/dgibson/maptest.tar.gz > > > > David> On a number of machines I've tested - both ppc64 and x86 - the > > David> SHARED version is consistently and significantly (50-100%) > > David> slower than the PRIVATE version. > > > > Just gave it a test on my laptop and server. Both are p3. The > > laptop is under heavier mem pressure; the server has just under > > a gig with most free/cache/buff. Laptop is still running 2.6.7 > > whereas the server is bk as of 2004-10-24. > > > > Buth took about 11 seconds for the private and around 30 seconds > > for the shared tests. > > > > I get the exact opposite, on a P4: > > vmm:/home/akpm/maptest> time ./mm-sharemmap > ./mm-sharemmap 10.81s user 0.05s system 100% cpu 10.855 total > vmm:/home/akpm/maptest> time ./mm-sharemmap > ./mm-sharemmap 11.04s user 0.05s system 100% cpu 11.086 total > vmm:/home/akpm/maptest> time ./mm-privmmap > ./mm-privmmap 26.91s user 0.02s system 100% cpu 26.903 total > vmm:/home/akpm/maptest> time ./mm-privmmap > ./mm-privmmap 26.89s user 0.02s system 100% cpu 26.894 total > vmm:/home/akpm/maptest> uname -a > Linux vmm 2.6.10-rc1-mm1 #14 SMP Tue Oct 26 23:23:23 PDT 2004 i686 i686 i386 GNU/Linux How very odd. I've now understood what was happening (see other post), but I'm not sure what could reverse the situation. Can you download the test tarball again - I've put up an updated version which pretouches the pages and gives some extra info. Running it both with and without pretouch would be interesting (#if 0/1 in matmul.h to change). > It's all user time so I can think of no reason apart from physical page > allocation order causing additional TLB reloads in one case. One is using > anonymous pages and the other is using shmem-backed pages, although I can't > think why that would make a difference. > > > Let's back out the no-buddy-bitmap patches: > > vmm:/home/akpm/maptest> time ./mm-sharemmap > ./mm-sharemmap 12.01s user 0.06s system 99% cpu 12.087 total > vmm:/home/akpm/maptest> time ./mm-sharemmap > ./mm-sharemmap 12.56s user 0.05s system 100% cpu 12.607 total > vmm:/home/akpm/maptest> time ./mm-privmmap > ./mm-privmmap 26.74s user 0.03s system 99% cpu 26.776 total > vmm:/home/akpm/maptest> time ./mm-privmmap > ./mm-privmmap 26.66s user 0.02s system 100% cpu 26.674 total > > much the same. > > Backing out "[PATCH] tweak the buddy allocator for better I/O merging" from > June 24 makes no difference. > -- David Gibson | For every complex problem there is a david AT gibson.dropbear.id.au | solution which is simple, neat and | wrong. http://www.ozlabs.org/people/dgibson - 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/