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Tue, 11 Jul 2023 03:00:45 -0400 X-MC-Unique: PfcYMSaXMaKpVE0zvE3fRA-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 2F6FA856506; Tue, 11 Jul 2023 07:00:44 +0000 (UTC) Received: from localhost (ovpn-12-93.pek2.redhat.com [10.72.12.93]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B333A492B01; Tue, 11 Jul 2023 07:00:05 +0000 (UTC) Date: Tue, 11 Jul 2023 14:59:35 +0800 From: Baoquan He To: Ming Lei Subject: Re: [PATCH 2/2] nvme-pci: use blk_mq_max_nr_hw_queues() to calculate io queues Message-ID: References: <20230708020259.1343736-1-ming.lei@redhat.com> <20230708020259.1343736-3-ming.lei@redhat.com> <20230710064109.GB24519@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jens Axboe , linuxppc-dev@lists.ozlabs.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org, linux-block@vger.kernel.org, Wen Xiong , Keith Busch , Thomas Gleixner , Dave Young , Christoph Hellwig , linux-arm-kernel@lists.infradead.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 07/11/23 at 11:53am, Ming Lei wrote: > Hi Baoquan, > > On Tue, Jul 11, 2023 at 11:35:50AM +0800, Baoquan He wrote: > > On 07/10/23 at 05:14pm, Ming Lei wrote: > > > On Mon, Jul 10, 2023 at 08:41:09AM +0200, Christoph Hellwig wrote: > > > > On Sat, Jul 08, 2023 at 10:02:59AM +0800, Ming Lei wrote: > > > > > Take blk-mq's knowledge into account for calculating io queues. > > > > > > > > > > Fix wrong queue mapping in case of kdump kernel. > > > > > > > > > > On arm and ppc64, 'maxcpus=1' is passed to kdump command line, see > > > > > `Documentation/admin-guide/kdump/kdump.rst`, so num_possible_cpus() > > > > > still returns all CPUs. > > > > > > > > That's simply broken. Please fix the arch code to make sure > > > > it does not return a bogus num_possible_cpus value for these > > > > > > That is documented in Documentation/admin-guide/kdump/kdump.rst. > > > > > > On arm and ppc64, 'maxcpus=1' is passed for kdump kernel, and "maxcpu=1" > > > simply keep one of CPU cores as online, and others as offline. > > > > I don't know maxcpus on arm and ppc64 well. But maxcpus=1 or nr_cpus=1 > > are suggested parameter. Because usually nr_cpus=1 is enough to make > > kdump kernel work well to capture vmcore. However, user is allowed to > > specify nr_cpus=n (n>1) if they think multiple cpus are needed in kdump > > kernel. Your hard coding of cpu number in kdump kernel may be not so > > reasonable. > > As I mentioned, for arm/ppc64, passing 'maxcpus=1' actually follows > Documentation/admin-guide/kdump/kdump.rst. > > 'nr_cpus=N' just works fine, so not related with this topic. > > After 'maxcpus=1' is passed, kernel only brings up one of cpu cores as > online during booting, and others still can be put into online by > userspace. Now this way causes IO timeout on some storage device which > uses managed irq and supports multiple io queues. > > Here the focus is if passing 'maxcpus=1' is valid for kdump > kernel, that is we want to hear from our arch/kdump guys. Yes, 'maxcpus=1' is valid and suggested on ppc64 for kdump kernel if needed, because there's no 'nr_cpus=' support on ppc64 yet. > > If yes, something needs to be fixed, such as, what this patchset is > doing. > > > > > Please cc kexec mailing list when posting so that people can view the > > whole thread of discussion. > > Already Cc kexe & arm/powerpc & irq list. > > > Thanks, > Ming >