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);
+}
+
+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 <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).
