From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752660AbbDAQMo (ORCPT ); Wed, 1 Apr 2015 12:12:44 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39377 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751210AbbDAQMm (ORCPT ); Wed, 1 Apr 2015 12:12:42 -0400 Message-ID: <551C18F4.2090407@redhat.com> Date: Wed, 01 Apr 2015 12:12:36 -0400 From: Rik van Riel User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Jens Axboe , Frederic Weisbecker CC: axboe@kernel.org, fweisbec@redhat.com, mingo@kernel.org, linux-kernel@vger.kernel.org, lcapitulino@redhat.com, mtosatti@redhat.com Subject: Re: [PATCH RFC] nohz,blk-mq: do not create blk-mq workqueues on nohz dedicated CPUs References: <20150331102726.076a6860@annuminas.surriel.com> <551AB81F.8020806@kernel.dk> <20150331153310.GB29033@lerouge> <551AC093.6080500@kernel.dk> In-Reply-To: <551AC093.6080500@kernel.dk> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/31/2015 11:43 AM, Jens Axboe wrote: > That'd be easy enough to do, that's how blk-mq handles offline CPUs as > well. The attached patch is completely untested, but will handle offline > or nohz CPUs in the same fashion - they will punt to hardware queue 0, > which is mapped to CPU0 (and others, depending on the queue vs CPU ratio). I have done some sanity testing with your patch, starting a KVM guest with vcpus and emulator threads all pinned to nohz_full cpus. The guest is still able to do disk IO, so things appear to work... Thanks for looking into this, Jens. Tested-by: Rik van Riel