From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752009AbdFGTHC (ORCPT ); Wed, 7 Jun 2017 15:07:02 -0400 Received: from verein.lst.de ([213.95.11.211]:54101 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751592AbdFGTHA (ORCPT ); Wed, 7 Jun 2017 15:07:00 -0400 Date: Wed, 7 Jun 2017 21:06:59 +0200 From: Christoph Hellwig To: Ming Lei Cc: Christoph Hellwig , Thomas Gleixner , Jens Axboe , Keith Busch , linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 7/8] blk-mq: create hctx for each present CPU Message-ID: <20170607190659.GA32550@lst.de> References: <20170603140403.27379-1-hch@lst.de> <20170603140403.27379-8-hch@lst.de> <20170607091038.GA25572@ming.t460p> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170607091038.GA25572@ming.t460p> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 07, 2017 at 05:10:46PM +0800, Ming Lei wrote: > One thing not sure is that we may need to handle new CPU hotplug > after initialization. Without the CPU hotplug handler, system may > not scale well when more CPUs are added to sockets. Adding physical CPUs to sockets is a very rare activity, and we should not optimize for it. Taking CPUs that are physically present offline and online is the case that is interesting, and that's what this patchset changes. > Another thing is that I don't see how NVMe handles this situation, > blk_mq_update_nr_hw_queues() is called in nvme_reset_work(), so > that means RESET need to be triggered after new CPUs are added to > system? Yes. > I have tried to add new CPUs runtime on Qemu, and not see > new hw queues are added no matter this patchset is applied or not. Do you even see the CPUs in your VM? For physical hotplug you'll need to reserve spots in the cpumap beforehand.