On Mon, Sep 06, 2021 at 01:31:32AM +0300, Max Gurtovoy wrote:
>
> On 9/5/2021 7:02 PM, Michael S. Tsirkin wrote:
> > 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 <mgurtovoy@xxxxxxxxxx>
> > > > ---
> > > >
> > > > 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);
> > > > +}
Hmm which tree is this for?
> > > > +
> > > > +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");
better:
+MODULE_PARM_DESC(num_io_request_queues,
+ "Limit number of IO request virt queues to use for each device. 0 for now limit");
> > > > +
> > > > 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 <stefanha@xxxxxxxxxx>
> > 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");
>
> The parameter is writable and can be changed and then new devices might be
> probed with new value.
>
> It can't be zero in the code. we can change param_set_uint_minmax args and
> say that 0 says nr_cpus.
>
> I'm ok with the renaming but I prefer to stick to the description we gave in
> V3 of this patch (and maybe enable value of 0 as mentioned above).
