From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752482Ab3JAU2P (ORCPT ); Tue, 1 Oct 2013 16:28:15 -0400 Received: from e39.co.us.ibm.com ([32.97.110.160]:58130 "EHLO e39.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751444Ab3JAU2D (ORCPT ); Tue, 1 Oct 2013 16:28:03 -0400 Date: Tue, 1 Oct 2013 13:27:56 -0700 From: "Paul E. McKenney" To: Tibor Billes Cc: linux-kernel@vger.kernel.org Subject: Re: Unusually high system CPU usage with recent kernels Message-ID: <20131001202756.GK5790@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20130914135951.288070@gmx.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130914135951.288070@gmx.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13100120-9332-0000-0000-0000019C71E4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Sep 14, 2013 at 03:59:51PM +0200, Tibor Billes wrote: > > From: Paul E. McKenney Sent: 09/13/13 02:19 AM > > On Wed, Sep 11, 2013 at 08:46:04AM +0200, Tibor Billes wrote: > > > > From: Paul E. McKenney Sent: 09/09/13 10:44 PM [ . . . ] > > > Sure. The attached tar file contains traces of good kernels. The first is with > > > version 3.9.7 (no patch applied) which was the last stable kernel I tried and > > > didn't have this issue. The second is version 3.11 with your fix applied. > > > Judging by the size of the traces, 3.11.0+ is still doing more work than > > > 3.9.7. > > > > Indeed, though quite a bit less than the problematic traces. > > > > Did you have all three patches applied to 3.11.0, or just the last one? > > If the latter, could you please try it with all three? > > Only the last one was applied to 3.11.0. The attachement now contains the > RCU trace with all thee applied. It seems to be smaller in size, but still > not close to 3.9.7. > > > > > > I'm not sure about LKML policies about attaching not-so-small files to > > > > > emails, so I've dropped LKML from the CC list. Please CC the mailing > > > > > list in your reply. > > > > > > > > Done! > > > > > > > > Another approach is to post the traces on the web and send the URL to > > > > LKML. But whatever works for you is fine by me. > > > > > > Sending directly to you won again :) Could you please CC the list in your > > > reply? > > > > Done! ;-) > > Could you please CC the list in your reply again? :) This trace is quite strange -- there are a number of processes that sleep and then wake up almost immediately, as in within a microsecond or so. I don't know why they would be doing that, and I also cannot think of what RCU might be doing to make them do that. I am unfortunately out of ideas on this one. Thanx, Paul