From: Andi Kleen Subject: Re: ext4 dbench performance with CONFIG_PREEMPT_RT Date: Fri, 09 Apr 2010 17:49:54 +0200 Message-ID: <87d3y8wrq5.fsf@basil.nowhere.org> References: <1270682478.3755.58.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: linux-ext4@vger.kernel.org, Mingming Cao , keith maanthey , Thomas Gleixner , Ingo Molnar , "Theodore Ts'o" , Darren Hart , tim.c.chen@intel.com To: john stultz Return-path: Received: from one.firstfloor.org ([213.235.205.2]:37958 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751031Ab0DIPuB (ORCPT ); Fri, 9 Apr 2010 11:50:01 -0400 In-Reply-To: <1270682478.3755.58.camel@localhost.localdomain> (john stultz's message of "Wed, 07 Apr 2010 16:21:18 -0700") Sender: linux-ext4-owner@vger.kernel.org List-ID: john stultz writes: > > Further using lockstat I was able to isolate it the contention down to > the journal j_state_lock, and then adding some lock owner tracking, I > was able to see that the lock owners were almost always in > start_this_handle, and jbd2_journal_stop when we saw contention (with > the freq breakdown being about 55% in jbd2_journal_stop and 45% in > start_this_handle). FWIW we've been also seeing this on larger systems without RT. The journal locks are the number one contention in some workloads. So it's not just a RT problem. -Andi -- ak@linux.intel.com -- Speaking for myself only.