From patchwork Fri Dec 18 21:44:10 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jan Kara X-Patchwork-Id: 11983011 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=-6.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT 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 B6743C3526B for ; Fri, 18 Dec 2020 21:45:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7D21F23B7B for ; Fri, 18 Dec 2020 21:45:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726145AbgLRVpC (ORCPT ); Fri, 18 Dec 2020 16:45:02 -0500 Received: from mx2.suse.de ([195.135.220.15]:52720 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725813AbgLRVpB (ORCPT ); Fri, 18 Dec 2020 16:45:01 -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 1EAEFAD0B; Fri, 18 Dec 2020 21:44:20 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id B2B541E132E; Fri, 18 Dec 2020 22:44:19 +0100 (CET) From: Jan Kara To: Jens Axboe Cc: , hare@suse.de, Kashyap Desai , Jan Kara Subject: [PATCH 0/2 RFC] blk-mq: Improve performance of non-mq IO schedulers with multiple HW queues Date: Fri, 18 Dec 2020 22:44:10 +0100 Message-Id: <20201218214412.1543-1-jack@suse.cz> X-Mailer: git-send-email 2.16.4 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org 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. 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. FWIW I'm not 100% sold on this approach, in particular I'm not sure it cannot cause some issues in higher-end setups but I want expect mq-deadline or BFQ to be used there. Anyway that's why I'm sending this as an RFC. Honza