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 916C0C4727E for ; Mon, 5 Oct 2020 08:38:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5DF032078D for ; Mon, 5 Oct 2020 08:38:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726053AbgJEIiV (ORCPT ); Mon, 5 Oct 2020 04:38:21 -0400 Received: from verein.lst.de ([213.95.11.211]:58129 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725893AbgJEIiU (ORCPT ); Mon, 5 Oct 2020 04:38:20 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id 5276867373; Mon, 5 Oct 2020 10:38:17 +0200 (CEST) Date: Mon, 5 Oct 2020 10:38:17 +0200 From: Christoph Hellwig To: Sagi Grimberg Cc: Christoph Hellwig , Leon Romanovsky , Doug Ledford , Jason Gunthorpe , Jens Axboe , Keith Busch , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-rdma@vger.kernel.org Subject: Re: [PATCH blk-next 1/2] blk-mq-rdma: Delete not-used multi-queue RDMA map queue code Message-ID: <20201005083817.GA14908@lst.de> References: <20200929091358.421086-1-leon@kernel.org> <20200929091358.421086-2-leon@kernel.org> <20200929102046.GA14445@lst.de> <20200929103549.GE3094@unreal> <879916e4-b572-16b9-7b92-94dba7e918a3@grimberg.me> <20201002064505.GA9593@lst.de> <14fab6a7-f7b5-2f9d-e01f-923b1c36816d@grimberg.me> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <14fab6a7-f7b5-2f9d-e01f-923b1c36816d@grimberg.me> User-Agent: Mutt/1.5.17 (2007-11-01) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 02, 2020 at 01:20:35PM -0700, Sagi Grimberg wrote: >> Well, why would they change it? The whole point of the infrastructure >> is that there is a single sane affinity setting for a given setup. Now >> that setting needed some refinement from the original series (e.g. the >> current series about only using housekeeping cpus if cpu isolation is >> in use). But allowing random users to modify affinity is just a receipe >> for a trainwreck. > > Well allowing people to mangle irq affinity settings seem to be a hard > requirement from the discussions in the past. > >> So I think we need to bring this back ASAP, as doing affinity right >> out of the box is an absolute requirement for sane performance without >> all the benchmarketing deep magic. > > Well, it's hard to say that setting custom irq affinity settings is > deemed non-useful to anyone and hence should be prevented. I'd expect > that irq settings have a sane default that works and if someone wants to > change it, it can but there should be no guarantees on optimal > performance. But IIRC this had some dependencies on drivers and some > more infrastructure to handle dynamic changes... The problem is that people change random settings. We need to generalize it into a sane API (e.g. the housekeeping CPUs thing which totally makes sense).