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=-5.3 required=3.0 tests=BAYES_00, 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 D74DEC55178 for ; Tue, 27 Oct 2020 18:04:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9977D21655 for ; Tue, 27 Oct 2020 18:04:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756932AbgJ0SEK (ORCPT ); Tue, 27 Oct 2020 14:04:10 -0400 Received: from mx2.suse.de ([195.135.220.15]:44866 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1824201AbgJ0SEJ (ORCPT ); Tue, 27 Oct 2020 14:04:09 -0400 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 3FBEBADCA; Tue, 27 Oct 2020 18:04:08 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id 3A0A5DA6E2; Tue, 27 Oct 2020 19:02:34 +0100 (CET) Date: Tue, 27 Oct 2020 19:02:34 +0100 From: David Sterba To: Anand Jain Cc: dsterba@suse.cz, linux-btrfs@vger.kernel.org, josef@toxicpanda.com, dsterba@suse.com Subject: Re: [PATCH v9 0/3] readmirror feature (read_policy sysfs and in-memory only approach) Message-ID: <20201027180233.GF6756@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Anand Jain , linux-btrfs@vger.kernel.org, josef@toxicpanda.com, dsterba@suse.com References: <20201023170403.GM6756@twin.jikos.cz> <31c3da05-2238-da84-509e-3b29835ec33a@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <31c3da05-2238-da84-509e-3b29835ec33a@oracle.com> User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Tue, Oct 27, 2020 at 09:52:11AM +0800, Anand Jain wrote: > > > On 24/10/20 1:04 am, David Sterba wrote: > > On Thu, Oct 22, 2020 at 03:43:34PM +0800, Anand Jain wrote: > >> v9: C coding style fixes in 1/3 and 3/3 > > > > So the point of adding the sysfs knobs is to allow testing various > > mirror selection strategies, what exactly was discussed in the past. Do > > you have patches for that as well? It does not need to be final and > > polished but at least give us something to test. > > > > Sure. I just sent out the patchset [1]. It provides read_policy: > latency, device, and round-robin. > > [1] > https://patchwork.kernel.org/project/linux-btrfs/list/?series=371023 Exporting more information from the devices would help us to decide but is there anything we can do just with what we have? Or eventually add our counters like for the in-flight requests or total bytes. The intention is not to duplicate what block layer does as we need to experiment with the stats and heuristics it's just for that purpose and we don't have to rely on other subsystem patches.