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,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 6A7AAC433DF for ; Fri, 26 Jun 2020 08:26:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4894F20775 for ; Fri, 26 Jun 2020 08:26:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726436AbgFZI0H (ORCPT ); Fri, 26 Jun 2020 04:26:07 -0400 Received: from verein.lst.de ([213.95.11.211]:50849 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725965AbgFZI0H (ORCPT ); Fri, 26 Jun 2020 04:26:07 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id F2D5968BFE; Fri, 26 Jun 2020 10:26:03 +0200 (CEST) Date: Fri, 26 Jun 2020 10:26:03 +0200 From: Christoph Hellwig To: Baolin Wang Cc: Christoph Hellwig , 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: <20200626082603.GB23888@lst.de> References: <32d99c016d23d660f5be4a9754b5b9aafe81ab6c.1592980985.git.baolin.wang@linux.alibaba.com> <20200624065258.GA18130@lst.de> <20200624075854.GA37292@VM20190228-100.tbsite.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200624075854.GA37292@VM20190228-100.tbsite.net> User-Agent: Mutt/1.5.17 (2007-11-01) 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 03:58:54PM +0800, Baolin Wang wrote: > 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. Please look up how saved features work in nvme.