From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756167Ab1BXObN (ORCPT ); Thu, 24 Feb 2011 09:31:13 -0500 Received: from mail-bw0-f46.google.com ([209.85.214.46]:43680 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754868Ab1BXObK (ORCPT ); Thu, 24 Feb 2011 09:31:10 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=PK/8lK88mP7nw/MKdnyBViPtQXEFh6gL+0e4+6z/umlEwV2L9u2fEObAc/cDUxbd3H K/r9JDu4Xfdqh2dQGVTXaUnixtSA2ZKFRxO8ccw2k0lrHER+iG5UqZJa3od+26aqGy+c BGuM5viXG9bK3vJLFqXBypULidl2YYCzhfnAo= Date: Thu, 24 Feb 2011 15:31:05 +0100 From: Tejun Heo To: Vivek Goyal Cc: linux kernel mailing list , libvir-list@redhat.com, Dominik Klein Subject: Re: Is it a workqueue related issue in 2.6.37 (Was: Re: [libvirt] blkio cgroup [solved]) Message-ID: <20110224143105.GL7840@htj.dyndns.org> References: <4D621B9B.3070205@in-telegence.net> <4D622002.2040604@in-telegence.net> <4D6222A8.6090303@in-telegence.net> <20110221184442.GM6428@redhat.com> <4D63BA3B.7070809@in-telegence.net> <20110222152426.GD28269@redhat.com> <20110222190953.GF28269@redhat.com> <4D650D7E.4050908@in-telegence.net> <4D662248.6040405@in-telegence.net> <20110224142303.GA18494@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110224142303.GA18494@redhat.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Thu, Feb 24, 2011 at 09:23:03AM -0500, Vivek Goyal wrote: > On Thu, Feb 24, 2011 at 10:18:00AM +0100, Dominik Klein wrote: > > Hi Dominik, > > Thanks for the tests and reports. I checked the latest logs also and > I see that cfq has scheduled a work but that work never gets scheduled. > I never see the trace message which says cfq_kick_queue(). > > I am ccing it to lkml and tejun to see if he has any suggestions. > > Tejun, > > I will give you some details about what we have discussed so far. > > Dominik is trying blkio throttling feature and trying to throttle some > virtual machines. He is using 2.6.37 kernels and once he launches 3 > virtual machines he notices that system is kind of frozen. After running > some traces we noticed that CFQ has requests but it is not dispatching > these to devices any more. > > This problem does not show up with deadline scheduler and also goes away > with 2.6.38-rc6 kernels. Hmmm... Maybe the following commit? commit 7576958a9d5a4a677ad7dd40901cdbb6c1110c98 Author: Tejun Heo Date: Mon Feb 14 14:04:46 2011 +0100 workqueue: wake up a worker when a rescuer is leaving a gcwq After executing the matching works, a rescuer leaves the gcwq whether there are more pending works or not. This may decrease the concurrency level to zero and stall execution until a new work item is queued on the gcwq. Make rescuer wake up a regular worker when it leaves a gcwq if there are more works to execute, so that execution isn't stalled. Signed-off-by: Tejun Heo Reported-by: Ray Jui Cc: stable@kernel.org -- tejun