From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S266527AbUGUD1x (ORCPT ); Tue, 20 Jul 2004 23:27:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266550AbUGUD1x (ORCPT ); Tue, 20 Jul 2004 23:27:53 -0400 Received: from viper.oldcity.dca.net ([216.158.38.4]:35767 "HELO viper.oldcity.dca.net") by vger.kernel.org with SMTP id S266527AbUGUD1u (ORCPT ); Tue, 20 Jul 2004 23:27:50 -0400 Subject: Re: [linux-audio-dev] Re: [announce] [patch] Voluntary Kernel Preemption Patch From: Lee Revell To: Ingo Molnar Cc: Andrew Morton , linux-audio-dev@music.columbia.edu, arjanv@redhat.com, linux-kernel In-Reply-To: <20040719102954.GA5491@elte.hu> References: <20040709182638.GA11310@elte.hu> <20040710222510.0593f4a4.akpm@osdl.org> <1089673014.10777.42.camel@mindpipe> <20040712163141.31ef1ad6.akpm@osdl.org> <1089677823.10777.64.camel@mindpipe> <20040712174639.38c7cf48.akpm@osdl.org> <20040719102954.GA5491@elte.hu> Content-Type: text/plain Message-Id: <1090380467.1212.3.camel@mindpipe> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 Date: Tue, 20 Jul 2004 23:27:48 -0400 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2004-07-19 at 06:29, Ingo Molnar wrote: > * Andrew Morton wrote: > > > > Should I try ext3? > > > > ext3 is certainly better than that, but still has a couple of > > potential problem spots. ext2 is probably the best at this time. > > with the voluntary-preempt patch applied ext3 is below ~500 usecs for > all things i tried on a 2GHz CPU. Without the patch i can trigger > latencies up to milliseconds (even with CONFIG_PREEMPT) by triggering a > bigger commit stream via some large file write or a cached du / causing > a stream of atime updates. (I very much suspect that all other > journalled filesystems have similar problems and they'll need > measurements and fixing just like ext3 does.) > > another bigger problem area is the VM - see my patch for details. > pagetable zapping and page reclaim are both problematic and need fixups > even under CONFIG_PREEMPT. Doing a simple 'make -j' kernel build that > hits swap triggers these easily. (after applying my patch the latencies > go below 1msec even with a 'make -j' overload.) > I discovered I can reliably produce a large XRUN by toggling Caps Lock, Scroll Lock, or Num Lock. This is with 2.6.8-rc1-mm1 + voluntary preempt (I modified the patch by hand to apply on this kernel, as 2.6.8-rc2 disables my network card). Here is the XRUN trace. ALSA /home/rlrevell/cvs/alsa-driver/alsa-kernel/core/pcm_lib.c:169: XRUN: pcmC0D0p [] dump_stack+0x17/0x20 [] snd_pcm_period_elapsed+0x2c7/0x400 [snd_pcm] [] snd_emu10k1_interrupt+0x337/0x3c0 [snd_emu10k1] [] handle_IRQ_event+0x33/0x60 [] do_IRQ+0xa5/0x170 [] common_interrupt+0x18/0x20 [] __delay+0xf/0x20 [] atkbd_sendbyte+0x5a/0xa0 [] atkbd_command+0x1d5/0x200 [] atkbd_event+0x16b/0x200 [] input_event+0x115/0x3d0 [] kbd_bh+0xbb/0x160 [] tasklet_action+0x44/0x70 [] __do_softirq+0x83/0x90 [] do_softirq+0x35/0x40 [] do_IRQ+0x115/0x170 [] common_interrupt+0x18/0x20 [] sys_read+0x2e/0x50 [] syscall_call+0x7/0xb Lee