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Tsirkin" To: Stefan Hajnoczi Cc: Max Gurtovoy , hch@infradead.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, israelr@nvidia.com, nitzanc@nvidia.com, oren@nvidia.com, linux-block@vger.kernel.org, axboe@kernel.dk Subject: Re: [PATCH v2 1/1] virtio-blk: add num_io_queues module parameter Message-ID: <20210905120234-mutt-send-email-mst@kernel.org> References: <20210831135035.6443-1-mgurtovoy@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Sep 02, 2021 at 02:45:52PM +0100, Stefan Hajnoczi wrote: > On Tue, Aug 31, 2021 at 04:50:35PM +0300, Max Gurtovoy wrote: > > Sometimes a user would like to control the amount of IO queues to be > > created for a block device. For example, for limiting the memory > > footprint of virtio-blk devices. > > > > Signed-off-by: Max Gurtovoy > > --- > > > > changes from v1: > > - use param_set_uint_minmax (from Christoph) > > - added "Should > 0" to module description > > > > Note: This commit apply on top of Jens's branch for-5.15/drivers > > --- > > drivers/block/virtio_blk.c | 20 +++++++++++++++++++- > > 1 file changed, 19 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c > > index 4b49df2dfd23..9332fc4e9b31 100644 > > --- a/drivers/block/virtio_blk.c > > +++ b/drivers/block/virtio_blk.c > > @@ -24,6 +24,22 @@ > > /* The maximum number of sg elements that fit into a virtqueue */ > > #define VIRTIO_BLK_MAX_SG_ELEMS 32768 > > > > +static int virtblk_queue_count_set(const char *val, > > + const struct kernel_param *kp) > > +{ > > + return param_set_uint_minmax(val, kp, 1, nr_cpu_ids); > > +} > > + > > +static const struct kernel_param_ops queue_count_ops = { > > + .set = virtblk_queue_count_set, > > + .get = param_get_uint, > > +}; > > + > > +static unsigned int num_io_queues; > > +module_param_cb(num_io_queues, &queue_count_ops, &num_io_queues, 0644); > > +MODULE_PARM_DESC(num_io_queues, > > + "Number of IO virt queues to use for blk device. Should > 0"); > > + > > static int major; > > static DEFINE_IDA(vd_index_ida); > > > > @@ -501,7 +517,9 @@ static int init_vq(struct virtio_blk *vblk) > > if (err) > > num_vqs = 1; > > > > - num_vqs = min_t(unsigned int, nr_cpu_ids, num_vqs); > > + num_vqs = min_t(unsigned int, > > + min_not_zero(num_io_queues, nr_cpu_ids), > > + num_vqs); > > If you respin, please consider calling them request queues. That's the > terminology from the VIRTIO spec and it's nice to keep it consistent. > But the purpose of num_io_queues is clear, so: > > Reviewed-by: Stefan Hajnoczi I did this: +static unsigned int num_io_request_queues; +module_param_cb(num_io_request_queues, &queue_count_ops, &num_io_request_queues, 0644); +MODULE_PARM_DESC(num_io_request_queues, + "Limit number of IO request virt queues to use for each device. 0 for now limit");