From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: Re: [PATCH v2 6/8] kvm tools: Add rwlock wrapper Date: Fri, 03 Jun 2011 10:54:19 +0300 Message-ID: <1307087659.13088.10.camel@lappy> References: <20110530095451.GB8461@elte.hu> <20110530201110.f3bf20b5.yoshikawa.takuya@oss.ntt.co.jp> <1306753954.14564.92.camel@lappy> <20110530202646.eff0ea28.yoshikawa.takuya@oss.ntt.co.jp> <4DE381DB.8040804@redhat.com> <20110530114949.GD22324@elte.hu> <4DE387DA.3020307@redhat.com> <20110530123602.GK22324@elte.hu> <1307086079.13088.8.camel@lappy> <20110603073427.GF15375@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Yinghai Lu , Avi Kivity , Takuya Yoshikawa , Pekka Enberg , kvm@vger.kernel.org, asias.hejun@gmail.com, gorcunov@gmail.com, prasadjoshi124@gmail.com, "Paul E. McKenney" , takuya.yoshikawa@gmail.com To: Ingo Molnar Return-path: Received: from mail-wy0-f174.google.com ([74.125.82.174]:35492 "EHLO mail-wy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751904Ab1FCHyY (ORCPT ); Fri, 3 Jun 2011 03:54:24 -0400 Received: by wya21 with SMTP id 21so1190234wya.19 for ; Fri, 03 Jun 2011 00:54:23 -0700 (PDT) In-Reply-To: <20110603073427.GF15375@elte.hu> Sender: kvm-owner@vger.kernel.org List-ID: On Fri, 2011-06-03 at 09:34 +0200, Ingo Molnar wrote: > * Sasha Levin wrote: > > > > with no apparent progress being made. > > > > Since it's something that worked in 2.6.37, I've looked into it to > > find what might have caused this issue. > > > > I've bisected guest kernels and found that the problem starts with: > > > > a26ac2455ffcf3be5c6ef92bc6df7182700f2114 is the first bad commit > > commit a26ac2455ffcf3be5c6ef92bc6df7182700f2114 > > Author: Paul E. McKenney > > Date: Wed Jan 12 14:10:23 2011 -0800 > > > > rcu: move TREE_RCU from softirq to kthread > > > > Ingo, could you confirm that the problem goes away for you when you > > use an earlier commit? > > testing will have to wait, but there's a recent upstream fix: > > d72bce0e67e8: rcu: Cure load woes > > That *might* perhaps address this problem too. > I've re-tested with Linus's current git, the problem is still there. > If not then this appears to be some sort of RCU related livelock with > brutally overcommitted vcpus. On native this would show up too, in a > less drastic form, as a spurious bootup delay. I don't think it was overcommited by *that* much. With that commit it usually hangs at 20-40 vcpus, while without it I can go up to 255. -- Sasha.