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_PASS,USER_AGENT_MUTT autolearn=ham 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 12642C43381 for ; Mon, 25 Mar 2019 09:50:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D77D420870 for ; Mon, 25 Mar 2019 09:50:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730519AbfCYJua (ORCPT ); Mon, 25 Mar 2019 05:50:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46158 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730216AbfCYJua (ORCPT ); Mon, 25 Mar 2019 05:50:30 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0F0CD30832CD; Mon, 25 Mar 2019 09:50:30 +0000 (UTC) Received: from ming.t460p (ovpn-8-18.pek2.redhat.com [10.72.8.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5E14D17156; Mon, 25 Mar 2019 09:50:16 +0000 (UTC) Date: Mon, 25 Mar 2019 17:50:13 +0800 From: Ming Lei To: Thomas Gleixner Cc: Peter Xu , Christoph Hellwig , Jason Wang , Luiz Capitulino , Linux Kernel Mailing List , "Michael S. Tsirkin" , minlei@redhat.com Subject: Re: Virtio-scsi multiqueue irq affinity Message-ID: <20190325095011.GA23225@ming.t460p> References: <20190318062150.GC6654@xz-x1> <20190325050213.GH9149@xz-x1> <20190325070616.GA9642@ming.t460p> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.1 (2017-09-22) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.44]); Mon, 25 Mar 2019 09:50:30 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 25, 2019 at 09:53:28AM +0100, Thomas Gleixner wrote: > Ming, > > On Mon, 25 Mar 2019, Ming Lei wrote: > > On Mon, Mar 25, 2019 at 01:02:13PM +0800, Peter Xu wrote: > > > One thing I can think of is the real-time scenario where "isolcpus=" > > > is provided, then logically we should not allow any isolated CPUs to > > > be bound to any of the multi-queue IRQs. Though Ming Lei and I had a > > > > So far, this behaviour is made by user-space. > > > > >From my understanding, IRQ subsystem doesn't handle "isolcpus=", even > > though the Kconfig help doesn't mention irq affinity affect: > > > > Make sure that CPUs running critical tasks are not disturbed by > > any source of "noise" such as unbound workqueues, timers, kthreads... > > Unbound jobs get offloaded to housekeeping CPUs. This is driven by > > the "isolcpus=" boot parameter. > > isolcpus has no effect on the interupts. That's what 'irqaffinity=' is for. Indeed. irq_default_affinity is built from 'irqaffinity=', however, we don't consider irq_default_affinity for managed IRQ affinity. Looks Peter wants to exclude some CPUs from the spread on managed IRQ. Thanks, Ming