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Tsirkin" To: Ming Lei Cc: Jens Axboe , Christoph Hellwig , linux-nvme@lists.infradead.org, "Martin K . Petersen" , linux-scsi@vger.kernel.org, linux-block@vger.kernel.org, Wen Xiong , Keith Busch , Jason Wang , virtualization@lists.linux-foundation.org Subject: Re: [PATCH V3 04/14] virtio-blk: limit max allowed submit queues Message-ID: <20230810152310-mutt-send-email-mst@kernel.org> References: <20230808104239.146085-1-ming.lei@redhat.com> <20230808104239.146085-5-ming.lei@redhat.com> MIME-Version: 1.0 In-Reply-To: <20230808104239.146085-5-ming.lei@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230810_122357_144217_B4CFB934 X-CRM114-Status: GOOD ( 23.11 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Tue, Aug 08, 2023 at 06:42:29PM +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 because 'maxcpus=1' just bring up one single > cpu core during booting. > > blk-mq sees single queue in kdump kernel, and in driver's viewpoint > there are still multiple queues, this inconsistency causes driver to apply > wrong queue mapping for handling IO, and IO timeout is triggered. > > Meantime, single queue makes much less resource utilization, and reduce > risk of kernel failure. > > Cc: Michael S. Tsirkin > Cc: Jason Wang > Cc: virtualization@lists.linux-foundation.org > Signed-off-by: Ming Lei superficially: Acked-by: Michael S. Tsirkin but this patch only makes sense if the rest of patchset is merged. feel free to merge directly. > --- > drivers/block/virtio_blk.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > index 1fe011676d07..4ba79fe2a1b4 100644 > --- a/drivers/block/virtio_blk.c > +++ b/drivers/block/virtio_blk.c > @@ -1047,7 +1047,8 @@ static int init_vq(struct virtio_blk *vblk) > > num_poll_vqs = min_t(unsigned int, poll_queues, num_vqs - 1); > > - vblk->io_queues[HCTX_TYPE_DEFAULT] = num_vqs - num_poll_vqs; > + vblk->io_queues[HCTX_TYPE_DEFAULT] = min_t(unsigned, > + num_vqs - num_poll_vqs, blk_mq_max_nr_hw_queues()); > vblk->io_queues[HCTX_TYPE_READ] = 0; > vblk->io_queues[HCTX_TYPE_POLL] = num_poll_vqs; > > -- > 2.40.1