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=-7.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 4392BC433E0 for ; Wed, 10 Feb 2021 13:02:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 00FF564DE3 for ; Wed, 10 Feb 2021 13:01:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231649AbhBJNBm (ORCPT ); Wed, 10 Feb 2021 08:01:42 -0500 Received: from rere.qmqm.pl ([91.227.64.183]:36286 "EHLO rere.qmqm.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231668AbhBJM7d (ORCPT ); Wed, 10 Feb 2021 07:59:33 -0500 Received: from remote.user (localhost [127.0.0.1]) by rere.qmqm.pl (Postfix) with ESMTPSA id 4DbKZX4sYxz6r; Wed, 10 Feb 2021 13:58:44 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=rere.qmqm.pl; s=1; t=1612961924; bh=CrEz6PwI0HJJcQyRSYFbySp7b7sxuUv30wgP5keoK7I=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=cbOP0DorpbnwPhgeBg/RJ85LhzJMZjIzOwzLX6BEOmMr+SdD2QxSkVs+Rg7M4lHXD +gSh1npIbqE6EyTcBaG+xPgtA8hh9pFaCfI2ONWG5Pl64/ihIxzPMsS1/rc+uH7RmG SNDqx6sOOQySG0A5ohwXVLb90fz5QsydW8BiE+pwAdt0Th7J1hEMlK/Q0oIb1/9Mj2 vqEC/mKH7DKR3+XdSClBvs0AlaCZEMrrIqb4ugLBIzdU1fjATYC+wwukDx94CxaNeB VKz3c8VxsFypEA9MF0FFS4zzd4NLwt971THkLPAJ1dgOnXUJc0yFsI/mhFWcu5nZX5 RPqUgDFgdG6bQ== X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.102.4 at mail Date: Wed, 10 Feb 2021 13:58:15 +0100 From: =?iso-8859-2?Q?Micha=B3_Miros=B3aw?= To: Michal Rostecki Cc: Chris Mason , Josef Bacik , David Sterba , "open list:BTRFS FILE SYSTEM" , open list , Michal Rostecki Subject: Re: [PATCH RFC 6/6] btrfs: Add roundrobin raid1 read policy Message-ID: <20210210125815.GA20903@qmqm.qmqm.pl> References: <20210209203041.21493-1-mrostecki@suse.de> <20210209203041.21493-7-mrostecki@suse.de> <20210210042428.GC12086@qmqm.qmqm.pl> <20210210122925.GB23499@wotan.suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-2 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20210210122925.GB23499@wotan.suse.de> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Wed, Feb 10, 2021 at 12:29:25PM +0000, Michal Rostecki wrote: > On Wed, Feb 10, 2021 at 05:24:28AM +0100, Michał Mirosław wrote: > > On Tue, Feb 09, 2021 at 09:30:40PM +0100, Michal Rostecki wrote: > > [...] > > > For the array with 3 HDDs, not adding any penalty resulted in 409MiB/s > > > (429MB/s) performance. Adding the penalty value 1 resulted in a > > > performance drop to 404MiB/s (424MB/s). Increasing the value towards 10 > > > was making the performance even worse. > > > > > > For the array with 2 HDDs and 1 SSD, adding penalty value 1 to > > > rotational disks resulted in the best performance - 541MiB/s (567MB/s). > > > Not adding any value and increasing the value was making the performance > > > worse. > > > > > > Adding penalty value to non-rotational disks was always decreasing the > > > performance, which motivated setting it as 0 by default. For the purpose > > > of testing, it's still configurable. > > [...] > > > + bdev = map->stripes[mirror_index].dev->bdev; > > > + inflight = mirror_load(fs_info, map, mirror_index, stripe_offset, > > > + stripe_nr); > > > + queue_depth = blk_queue_depth(bdev->bd_disk->queue); > > > + > > > + return inflight < queue_depth; > > [...] > > > + last_mirror = this_cpu_read(*fs_info->last_mirror); > > [...] > > > + for (i = last_mirror; i < first + num_stripes; i++) { > > > + if (mirror_queue_not_filled(fs_info, map, i, stripe_offset, > > > + stripe_nr)) { > > > + preferred_mirror = i; > > > + goto out; > > > + } > > > + } > > > + > > > + for (i = first; i < last_mirror; i++) { > > > + if (mirror_queue_not_filled(fs_info, map, i, stripe_offset, > > > + stripe_nr)) { > > > + preferred_mirror = i; > > > + goto out; > > > + } > > > + } > > > + > > > + preferred_mirror = last_mirror; > > > + > > > +out: > > > + this_cpu_write(*fs_info->last_mirror, preferred_mirror); > > > > This looks like it effectively decreases queue depth for non-last > > device. After all devices are filled to queue_depth-penalty, only > > a single mirror will be selected for next reads (until a read on > > some other one completes). > > > > Good point. And if all devices are going to be filled for longer time, > this function will keep selecting the last one. Maybe I should select > last+1 in that case. Would that address your concern or did you have any > other solution in mind? The best would be to postpone the selection until one device becomes free again. But if that's not doable, then yes, you could make sure it stays round-robin after filling the queues (the scheduling will loose the "penalty"-driven adjustment though). Best Reagrds, Michał Mirosław