On Thu, Sep 02, 2021 at 11:46:22PM +0300, Max Gurtovoy wrote:
> Sometimes a user would like to control the amount of request queues to
> be created for a block device. For example, for limiting the memory
> footprint of virtio-blk devices.
>
> Reviewed-by: Christoph Hellwig <hch@xxxxxx>
> Reviewed-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
> Signed-off-by: Max Gurtovoy <mgurtovoy@xxxxxxxxxx>
> ---
>
> changes from v2:
> - renamed num_io_queues to num_request_queues (from Stefan)
> - added Reviewed-by signatures (from Stefan and Christoph)
>
> 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 | 21 ++++++++++++++++++++-
> 1 file changed, 20 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 4b49df2dfd23..aaa2833a4734 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -24,6 +24,23 @@
> /* 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_request_queues;
> +module_param_cb(num_request_queues, &queue_count_ops, &num_request_queues,
> + 0644);
> +MODULE_PARM_DESC(num_request_queues,
> + "Number of request queues to use for blk device. Should > 0");
> +
Won't it limit all virtio block devices to the same limit?
It is very common to see multiple virtio-blk devices on the same system
and they probably need different limits.
Thanks
