[1/2] virtio-blk: make queue size configurable

Commit Message

Mark Kanda Dec. 6, 2017, 7:54 p.m. UTC

Depending on the configuration, it can be beneficial to adjust the virtio-blk
queue size to something other than the current default of 128. Add a new
property to make the queue size configurable.

Signed-off-by: Mark Kanda <[e-mail]>
Reviewed-by: Karl Heubaum <[e-mail]>
Reviewed-by: Martin K. Petersen <[e-mail]>
Reviewed-by: Ameya More <[e-mail]>
---
 hw/block/virtio-blk.c          | 7 ++++++-
 include/hw/virtio/virtio-blk.h | 1 +
 2 files changed, 7 insertions(+), 1 deletion(-)

Comments

Stefan Hajnoczi Dec. 8, 2017, 10:13 a.m. UTC | #1

On Wed, Dec 06, 2017 at 01:54:00PM -0600, Mark Kanda wrote:
> Depending on the configuration, it can be beneficial to adjust the virtio-blk
> queue size to something other than the current default of 128. Add a new
> property to make the queue size configurable.
> 
> Signed-off-by: Mark Kanda <[e-mail]>
> Reviewed-by: Karl Heubaum <[e-mail]>
> Reviewed-by: Martin K. Petersen <[e-mail]>
> Reviewed-by: Ameya More <[e-mail]>
> ---
>  hw/block/virtio-blk.c          | 7 ++++++-
>  include/hw/virtio/virtio-blk.h | 1 +
>  2 files changed, 7 insertions(+), 1 deletion(-)

Please see commit 9b02e1618cf26aa52cf786f215d757506dda14f8 ("virtio-net:
enable configurable tx queue size") for additional considerations.
QEMU's virtio implementation hardcodes the maximum queue size at 1024
and this limit must be checked.

Patch

diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index 05d1440..002c56f 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -928,6 +928,10 @@  static void virtio_blk_device_realize(DeviceState *dev, Error **errp)
         error_setg(errp, "num-queues property must be larger than 0");
         return;
     }
+    if (!is_power_of_2(conf->queue_size)) {
+        error_setg(errp, "queue-size property must be a power of 2");
+        return;
+    }
 
     blkconf_serial(&conf->conf, &conf->serial);
     blkconf_apply_backend_options(&conf->conf,
@@ -953,7 +957,7 @@  static void virtio_blk_device_realize(DeviceState *dev, Error **errp)
     s->sector_mask = (s->conf.conf.logical_block_size / BDRV_SECTOR_SIZE) - 1;
 
     for (i = 0; i < conf->num_queues; i++) {
-        virtio_add_queue(vdev, 128, virtio_blk_handle_output);
+        virtio_add_queue(vdev, conf->queue_size, virtio_blk_handle_output);
     }
     virtio_blk_data_plane_create(vdev, conf, &s->dataplane, &err);
     if (err != NULL) {
@@ -1012,6 +1016,7 @@  static Property virtio_blk_properties[] = {
     DEFINE_PROP_BIT("request-merging", VirtIOBlock, conf.request_merging, 0,
                     true),
     DEFINE_PROP_UINT16("num-queues", VirtIOBlock, conf.num_queues, 1),
+    DEFINE_PROP_UINT16("queue-size", VirtIOBlock, conf.queue_size, 128),
     DEFINE_PROP_LINK("iothread", VirtIOBlock, conf.iothread, TYPE_IOTHREAD,
                      IOThread *),
     DEFINE_PROP_END_OF_LIST(),
diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
index d3c8a6f..5117431 100644
--- a/include/hw/virtio/virtio-blk.h
+++ b/include/hw/virtio/virtio-blk.h
@@ -39,6 +39,7 @@  struct VirtIOBlkConf
     uint32_t config_wce;
     uint32_t request_merging;
     uint16_t num_queues;
+    uint16_t queue_size;
 };
 
 struct VirtIOBlockDataPlane;