Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755771Ab0FPOzi (ORCPT ); Wed, 16 Jun 2010 10:55:38 -0400 Received: from mail-vw0-f46.google.com ([209.85.212.46]:49424 "EHLO mail-vw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752189Ab0FPOzg convert rfc822-to-8bit (ORCPT ); Wed, 16 Jun 2010 10:55:36 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:content-type :content-transfer-encoding; b=fBVIbrAzKZ5iMueQDv+LCXB6YS8va/c/89g6Em34ZgEglKPRpT8q7u20fgTNPISqX6 xgy1UWz10xfKyqjyHUGwOFG+sICDD674ATMT2uh65ZK8YJ+YJ6gVSM1F8jV+Wz9G67Ua o8K8KbwB0vwhb659TuD5H/9/1K4Qqza4gKkgw= MIME-Version: 1.0 In-Reply-To: <20100616143659.GA14616@elliptictech.com> References: <20100613194949.GC8055@thunk.org> <20100614184244.GA11480@elliptictech.com> <20100614214646.GF6666@thunk.org> <18402.1276625268@redhat.com> <20100616143659.GA14616@elliptictech.com> Date: Wed, 16 Jun 2010 15:55:30 +0100 X-Google-Sender-Auth: QrWqnS7T1BPG8aqsnfRc8diEQFU Message-ID: Subject: Re: Why is kslowd accumulating so much CPU time? From: Andy Whitcroft To: Andy Whitcroft , David Howells , tytso@mit.edu, Dave Airlie , Dave Airlie , linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1963 Lines: 44 On Wed, Jun 16, 2010 at 3:36 PM, Nick Bowler wrote: > On 12:37 Wed 16 Jun ? ? , Andy Whitcroft wrote: >> > Can you see what they're doing? >> > >> > ? ? ? ?watch -n0 cat /sys/kernel/debug/slow_work/runqueue >> >> Turned on the debugging and applied the patch from Ted, and when >> things are bad I see constant cycling of all four threads in the >> output showing similar to the below, note only one thread shows at a >> time: >> >> Every 0.1s: cat /sys/kernel/debug/slow_work/runqueue ? ?Wed Jun 16 12:34:52 2010 >> >> THR PID ? ITEM ADDR ? ? ? ?FL MARK ?DESC >> === ===== ================ == ===== ========== >> ? ?0 ? 897 ffff88012bb07510 12 ?20ms DRM_CRTC_HELPER: i915@pci:0000:00:02.0 > > Indeed, this looks very similar to mine, except my DESC field is blank > for some reason. ?The FL value is sometimes 12, sometimes 2. DESC is only filled in if you have Ted's patch applied (earlier in this thread). > When things are bad, all four of the kslowd threads are pegged at 16% > CPU usage. ?On my T500, they _never_ calm down once they're pegged. > However, things seem to be working normally at boot. ?It seems that > there is some initial trigger which pegs the threads, then the cursor > lag and other problems are just fallout after that. ?The system is > essentially unusable after this point. > > The threads sometimes get pegged immediately after booting the system, > sometimes it can last an hour or more before showing any problems. > Unfortunately, this is making bisection essentially impossible. > > This seems to have been introduced somewhere between 2.6.35-rc1 and I suspect this is introduced by the commit which pulled polling of DRM connectors into the core. -apw -- 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/