Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758132Ab0FPNde (ORCPT ); Wed, 16 Jun 2010 09:33:34 -0400 Received: from mail-gy0-f174.google.com ([209.85.160.174]:45155 "EHLO mail-gy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755951Ab0FPNdc convert rfc822-to-8bit (ORCPT ); Wed, 16 Jun 2010 09:33:32 -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:cc:content-type :content-transfer-encoding; b=lQQfOSDUO3+2QVUblL6EibRh1T2bOJyzDpbkv9lEDP5UA5g2VaIhigL3tZmWqeX8jW pblMxJ7XTD91oEi2trrPsK0zu3+lEJs+8hjzLcAHFSd8BteGyYhuyhyrthuyySJ5FQTH FoJ+l/Mrc2/hW8SXDgE0JZ5YJ0PNmpVWd7gs4= MIME-Version: 1.0 In-Reply-To: References: <20100613194949.GC8055@thunk.org> <20100614184244.GA11480@elliptictech.com> <20100614214646.GF6666@thunk.org> <18402.1276625268@redhat.com> Date: Wed, 16 Jun 2010 14:33:31 +0100 X-Google-Sender-Auth: pUhSVHCrhwfmRhrALHLLDG2QLQU Message-ID: Subject: Re: Why is kslowd accumulating so much CPU time? From: Andy Whitcroft To: David Howells Cc: 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: 2565 Lines: 55 On Wed, Jun 16, 2010 at 12:37 PM, 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 > > When things are working well I see the same output appearing for one > update, about every 10s. Ok I've added some additional debug and these appear to be being thrown a loop by the HPD interrupt which is firing continiusly, here is a sample from some 4 minutes after boot: [ 284.862670] APW: drm_helper_hpd_irq_event: cancel/submit [ 284.882803] APW: drm_helper_hpd_irq_event: cancel/submit [ 284.902691] APW: drm_helper_hpd_irq_event: cancel/submit [ 284.922814] APW: drm_helper_hpd_irq_event: cancel/submit [ 284.942620] APW: drm_helper_hpd_irq_event: cancel/submit [ 284.962707] APW: drm_helper_hpd_irq_event: cancel/submit [ 284.982937] APW: drm_helper_hpd_irq_event: cancel/submit [ 285.004181] APW: drm_helper_hpd_irq_event: cancel/submit [ 285.022622] APW: drm_helper_hpd_irq_event: cancel/submit [ 285.042569] APW: drm_helper_hpd_irq_event: cancel/submit [ 285.062593] APW: drm_helper_hpd_irq_event: cancel/submit [ 285.082683] APW: drm_helper_hpd_irq_event: cancel/submit Later when things calm down we see them but much much less often: [ 379.038239] APW: drm_helper_hpd_irq_event: cancel/submit [ 379.044904] APW: drm_helper_hpd_irq_event: cancel/submit [ 382.438106] APW: drm_helper_hpd_irq_event: cancel/submit [ 382.444754] APW: drm_helper_hpd_irq_event: cancel/submit [ 385.838072] APW: drm_helper_hpd_irq_event: cancel/submit [ 385.844735] APW: drm_helper_hpd_irq_event: cancel/submit [ 389.237876] APW: drm_helper_hpd_irq_event: cancel/submit [ 389.244523] APW: drm_helper_hpd_irq_event: cancel/submit [ 392.638048] APW: drm_helper_hpd_irq_event: cancel/submit [ 392.644740] APW: drm_helper_hpd_irq_event: cancel/submit -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/