From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758289AbbIDHja (ORCPT ); Fri, 4 Sep 2015 03:39:30 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:34543 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755257AbbIDHj2 (ORCPT ); Fri, 4 Sep 2015 03:39:28 -0400 Date: Fri, 4 Sep 2015 09:39:17 +0200 From: Peter Zijlstra To: Linus Torvalds Cc: Dave Chinner , Linux Kernel Mailing List , Waiman Long , Ingo Molnar Subject: Re: [4.2, Regression] Queued spinlocks cause major XFS performance regression Message-ID: <20150904073917.GA18489@twins.programming.kicks-ass.net> References: <20150904054820.GY3902@dastard> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 03, 2015 at 11:39:21PM -0700, Linus Torvalds wrote: > On Thu, Sep 3, 2015 at 10:48 PM, Dave Chinner wrote: > > > > When I turned spinlock debugging off on 4.2 to get some perf numbers > > a request from Linus, I got this: > > To confirm that this is indeed caused by the queued spinlocks, I > > removed the the spinlock debugging and did this to arch/x86/Kconfig: > > > > - select ARCH_USE_QUEUED_SPINLOCK > > > > And the results are: > Is this a PARAVIRT configuration? There were issues with PV > interaction at some point. If it is PV, and you don't actually use PV, > can you test with PV support disabled? His earlier instructions on how to reproduce do indeed have the workload running inside a VM. Dave, can you confirm you're still running this in a VM, and can you provide your full guest .config? In particular the PARAVIRT_SPINLOCKS option is interesting. Also, are you doing anything special with the host? I'll try and poke at this, but I'm not much into this whole VM thing so it'll probably be a while before I even have a simple guest running :/