Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752240AbbD3K64 (ORCPT ); Thu, 30 Apr 2015 06:58:56 -0400 Received: from mail.phunq.net ([184.71.0.62]:46216 "EHLO starbase.phunq.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751783AbbD3K6w convert rfc822-to-8bit (ORCPT ); Thu, 30 Apr 2015 06:58:52 -0400 From: Daniel Phillips To: Mike Galbraith Cc: , , , "Theodore Ts'o" , OGAWA Hirofumi Subject: Re: Tux3 Report: How fast can we =?iso-8859-1?Q?fsync=3F?= Date: Thu, 30 Apr 2015 03:59:08 -0700 User-Agent: Trojita/v0.5-14-g8a2496c; Qt/4.8.6; X11; Linux; Ubuntu 14.04.2 LTS MIME-Version: 1.0 Message-ID: <7322d870-e627-4ba4-91b4-bcb38ad8d015@phunq.net> In-Reply-To: <1430365857.3180.18.camel@gmail.com> References: <8f886f13-6550-4322-95be-93244ae61045@phunq.net> <1430274071.3363.4.camel@gmail.com> <1906f271-aa23-404b-9776-a4e2bce0c6aa@phunq.net> <1430289213.3693.3.camel@gmail.com> <1430325763.19371.41.camel@gmail.com> <1430365857.3180.18.camel@gmail.com> Organization: tux3.org Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1103 Lines: 27 On Wednesday, April 29, 2015 8:50:57 PM PDT, Mike Galbraith wrote: > On Wed, 2015-04-29 at 13:40 -0700, Daniel Phillips wrote: >> >> That order of magnitude latency difference is striking. It sounds >> good, but what does it mean? I see a smaller difference here, maybe >> because of running under KVM. > > That max_latency thing is flush. Right, it is just the max run time of all operations, including flush (dbench's name for fsync I think) which would most probably be the longest running one. I would like to know how we manage to pull that off. Now that you mention it, I see a factor of two or so latency win here, not the order of magnitude that you saw. Maybe KVM introduces some fuzz for me. I checked whether fsync = sync is the reason, and no. Well, that goes on the back burner, we will no doubt figure it out in due course. Regards, Daniel -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/