From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DAD4AC282CE for ; Wed, 22 May 2019 10:01:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BB8252070D for ; Wed, 22 May 2019 10:01:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729435AbfEVKBf (ORCPT ); Wed, 22 May 2019 06:01:35 -0400 Received: from outgoing-stata.csail.mit.edu ([128.30.2.210]:48279 "EHLO outgoing-stata.csail.mit.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729414AbfEVKBe (ORCPT ); Wed, 22 May 2019 06:01:34 -0400 Received: from c-73-193-85-113.hsd1.wa.comcast.net ([73.193.85.113] helo=srivatsab-a01.vmware.com) by outgoing-stata.csail.mit.edu with esmtpsa (TLS1.2:RSA_AES_128_CBC_SHA1:128) (Exim 4.82) (envelope-from ) id 1hTO3s-000DFW-EO; Wed, 22 May 2019 06:01:28 -0400 Subject: Re: CFQ idling kills I/O performance on ext4 with blkio cgroup controller To: Paolo Valente Cc: linux-fsdevel@vger.kernel.org, linux-block , linux-ext4@vger.kernel.org, cgroups@vger.kernel.org, kernel list , Jens Axboe , Jan Kara , jmoyer@redhat.com, Theodore Ts'o , amakhalov@vmware.com, anishs@vmware.com, srivatsab@vmware.com References: <8d72fcf7-bbb4-2965-1a06-e9fc177a8938@csail.mit.edu> <1812E450-14EF-4D5A-8F31-668499E13652@linaro.org> <46c6a4be-f567-3621-2e16-0e341762b828@csail.mit.edu> <07D11833-8285-49C2-943D-E4C1D23E8859@linaro.org> <5B6570A2-541A-4CF8-98E0-979EA6E3717D@linaro.org> <2CB39B34-21EE-4A95-A073-8633CF2D187C@linaro.org> <0e3fdf31-70d9-26eb-7b42-2795d4b03722@csail.mit.edu> <686D6469-9DE7-4738-B92A-002144C3E63E@linaro.org> From: "Srivatsa S. Bhat" Message-ID: <01d55216-5718-767a-e1e6-aadc67b632f4@csail.mit.edu> Date: Wed, 22 May 2019 03:01:24 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <686D6469-9DE7-4738-B92A-002144C3E63E@linaro.org> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 5/22/19 2:09 AM, Paolo Valente wrote: > > First, thank you very much for testing my patches, and, above all, for > sharing those huge traces! > > According to the your traces, the residual 20% lower throughput that you > record is due to the fact that the BFQ injection mechanism takes a few > hundredths of seconds to stabilize, at the beginning of the workload. > During that setup time, the throughput is equal to the dreadful ~60-90 KB/s > that you see without this new patch. After that time, there > seems to be no loss according to the trace. > > The problem is that a loss lasting only a few hundredths of seconds is > however not negligible for a write workload that lasts only 3-4 > seconds. Could you please try writing a larger file? > I tried running dd for longer (about 100 seconds), but still saw around 1.4 MB/s throughput with BFQ, and between 1.5 MB/s - 1.6 MB/s with mq-deadline and noop. But I'm not too worried about that difference. > In addition, I wanted to ask you whether you measured BFQ throughput > with traces disabled. This may make a difference. > The above result (1.4 MB/s) was obtained with traces disabled. > After trying writing a larger file, you can try with low_latency on. > On my side, it causes results to become a little unstable across > repetitions (which is expected). > With low_latency on, I get between 60 KB/s - 100 KB/s. Regards, Srivatsa VMware Photon OS