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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 6208BC433E0 for ; Wed, 20 Jan 2021 14:53:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1476B2336D for ; Wed, 20 Jan 2021 14:53:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731226AbhATOwD (ORCPT ); Wed, 20 Jan 2021 09:52:03 -0500 Received: from mx2.suse.de ([195.135.220.15]:45794 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390539AbhATOOY (ORCPT ); Wed, 20 Jan 2021 09:14:24 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 630ABAB7F; Wed, 20 Jan 2021 13:55:04 +0000 (UTC) Date: Wed, 20 Jan 2021 13:54:57 +0000 From: Michal Rostecki To: Anand Jain Cc: linux-btrfs@vger.kernel.org, dsterba@suse.com, josef@toxicpanda.com Subject: Re: [PATCH v3 1/4] btrfs: add read_policy latency Message-ID: <20210120135457.GA6831@wotan.suse.de> References: <64bb4905dc4b77e9fa22d8ba2635a36d15a33469.1610324448.git.anand.jain@oracle.com> <20210120102742.GA4584@wotan.suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Wed, Jan 20, 2021 at 08:30:56PM +0800, Anand Jain wrote: > I ran fio tests again, now with dstat in an another window. I don't > notice any such stalls, the read numbers went continuous until fio > finished. Could you please check with the below fio command, also > could you please share your fio command options. That's the fio config I used: https://gitlab.com/vadorovsky/playground/-/blob/master/fio/btrfs-raid1-seqread.fio The main differences seem to be: - the number of jobs (I used the number of CPU threads) - direct vs buffered I/O > > fio \ > --filename=/btrfs/largefile \ > --directory=/btrfs \ > --filesize=50G \ > --size=50G \ > --bs=64k \ > --ioengine=libaio \ > --rw=read \ > --direct=1 \ > --numjobs=1 \ > --group_reporting \ > --thread \ > --name iops-test-job > > It is system specific? With this command, dstat output looks good: https://paste.opensuse.org/view/simple/93159623 So I think it might be specific to whether we test direct of buffered I/O. Or to the number of jobs (single vs multiple jobs). Since the most of I/O on production environments is usually buffered, I think we should test with direct=0 too. Cheers, Michal