From: Ted Ts'o Subject: Re: [RFC, PATCH] Avoid hot statistics cache line in ext4 extent cache Date: Fri, 13 Apr 2012 14:48:23 -0400 Message-ID: <20120413184823.GA5898@thunk.org> References: <4F70F51F.8030405@linux.intel.com> <20120326235707.GC19489@thunk.org> <1334339612.3796.2.camel@schen9-DESK> <1334341876.3796.8.camel@schen9-DESK> <20120413183722.GG26332@thunk.org> <20120413184158.GZ17822@one.firstfloor.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Tim Chen , Linus Torvalds , Vivek Haldar , Andreas Dilger , linux-ext4@vger.kernel.org To: Andi Kleen Return-path: Received: from li9-11.members.linode.com ([67.18.176.11]:56797 "EHLO test.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755976Ab2DMSs3 (ORCPT ); Fri, 13 Apr 2012 14:48:29 -0400 Content-Disposition: inline In-Reply-To: <20120413184158.GZ17822@one.firstfloor.org> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Fri, Apr 13, 2012 at 08:41:58PM +0200, Andi Kleen wrote: > > The reason why I ask this is we're seeing anything like this with Eric > > Whitney's 48 CPU scalability testing; we're not CPU bottlenecked, and > > I don't even see evidence of a larger than usual CPU utilization > > compared to other file systems. > > I bet Eric didn't test with this statistic counter. Huh? You can't turn it off, and he's been doing regular scalability tests at least once per kernel release. Can you say a bit more about exactly how you are doing this test and what are the "other issues" where this is becoming a bottleneck? If possible I'd like to ask Eric if he can add it to his regular scalability tests. Thanks, - Ted