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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 20995C433E9 for ; Wed, 3 Feb 2021 16:54:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D7E2264F7C for ; Wed, 3 Feb 2021 16:54:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231372AbhBCQyy (ORCPT ); Wed, 3 Feb 2021 11:54:54 -0500 Received: from mx2.suse.de ([195.135.220.15]:51032 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230229AbhBCQyt (ORCPT ); Wed, 3 Feb 2021 11:54:49 -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 CB4C5AC45; Wed, 3 Feb 2021 16:54:04 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 4A8BA1E14C4; Wed, 3 Feb 2021 17:54:04 +0100 (CET) Date: Wed, 3 Feb 2021 17:54:04 +0100 From: Jan Kara To: John Garry Cc: Jens Axboe , Jan Kara , linux-block@vger.kernel.org, Ming Lei Subject: Re: [PATCH 0/2 v3] blk-mq: Improve performance of non-mq IO schedulers with multiple HW queues Message-ID: <20210203165404.GE7094@quack2.suse.cz> References: <20210111164717.21937-1-jack@suse.cz> <7afa35b2-cf35-a149-d325-3ad2ae8d8935@kernel.dk> <8b871c07-a516-36ae-75c2-7d0a153ea753@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8b871c07-a516-36ae-75c2-7d0a153ea753@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed 03-02-21 16:18:59, John Garry wrote: > On 25/01/2021 01:20, Jens Axboe wrote: > > On 1/11/21 9:47 AM, Jan Kara wrote: > > > Hello! > > > > > > This patch series aims to fix a regression we've noticed on our test grid when > > > support for multiple HW queues in megaraid_sas driver was added during the 5.10 > > > cycle (103fbf8e4020 scsi: megaraid_sas: Added support for shared host tagset > > > for cpuhotplug). The commit was reverted in the end for other reasons but I > > > believe the fundamental problem still exists for any other similar setup. > > That commit made it into 5.11-rc, and other SCSI HBA expose HW queues in > 5.10 and earlier. But then this series is targeted at 5.12. > > Question: can we consider backport this series just due to performance issue > regression? I'd say no, but maybe someone strongly disagrees with me ... I also don't consider my series a stable tree material. The setup of multiple HW queues with BFQ IO scheduler isn't really very common... Honza > > Thanks, > John > > > The > > > problem manifests when the storage card supports multiple hardware queues > > > however storage behind it is slow (single rotating disk in our case) and so > > > using IO scheduler such as BFQ is desirable. See the second patch for details. > -- Jan Kara SUSE Labs, CR