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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,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 3C23FC433DF for ; Wed, 24 Jun 2020 07:58:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1E50520899 for ; Wed, 24 Jun 2020 07:58:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390159AbgFXH65 (ORCPT ); Wed, 24 Jun 2020 03:58:57 -0400 Received: from out30-130.freemail.mail.aliyun.com ([115.124.30.130]:54326 "EHLO out30-130.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388836AbgFXH65 (ORCPT ); Wed, 24 Jun 2020 03:58:57 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R671e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e01355;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0U0aLOJ8_1592985534; Received: from localhost(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0U0aLOJ8_1592985534) by smtp.aliyun-inc.com(127.0.0.1); Wed, 24 Jun 2020 15:58:54 +0800 Date: Wed, 24 Jun 2020 15:58:54 +0800 From: Baolin Wang To: Christoph Hellwig Cc: kbusch@kernel.org, axboe@fb.com, sagi@grimberg.me, baolin.wang7@gmail.com, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] nvme: Add Arbitration Burst support Message-ID: <20200624075854.GA37292@VM20190228-100.tbsite.net> Reply-To: Baolin Wang References: <32d99c016d23d660f5be4a9754b5b9aafe81ab6c.1592980985.git.baolin.wang@linux.alibaba.com> <20200624065258.GA18130@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200624065258.GA18130@lst.de> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 24, 2020 at 08:52:58AM +0200, Christoph Hellwig wrote: > On Wed, Jun 24, 2020 at 02:49:57PM +0800, Baolin Wang wrote: > > >From the NVMe spec, "In order to make efficient use of the non-volatile > > memory, it is often advantageous to execute multiple commands from a > > Submission Queue in parallel. For Submission Queues that are using > > weighted round robin with urgent priority class or round robin > > arbitration, host software may configure an Arbitration Burst setting". > > Thus add Arbitration Burst setting support. > > What is the value add of doing this in the kernel? Wouldn't a nvme-cli > subcommand to just set the arbitration burst to the recommended value, > either as a saved or current value be both more useful and also cause > less kernel bloat? Yes, that's another way to configure the RAB, but for some simple and frequently-used usage cases, we just want to use the recommanded arbitration burst as default without bothering the nvme-cli tool every reset time.