virtio-blk: use larger default request size

Bump default from 8 to 64 blocks.  Using 8 by default leads
to requests being splitted on qemu, which slows down boot.

Some (temporary) debug logging added showed that almost all
requests on a standard fedora install are less than 64 blocks,
so that should bring us back to 1.15 performance levels.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

diff --git a/src/hw/virtio-blk.c b/src/hw/virtio-blk.c
index 929ba8873dc01d06c96bd978c7f03862727eff8e..9b4a05a4c4245723b88a5d79dc2e320eb664fb46 100644 (file)
--- a/src/hw/virtio-blk.c
+++ b/src/hw/virtio-blk.c
@@ -95,7 +95,7 @@ virtio_blk_op(struct disk_op_s *op, int write)
         blk_num_max = (u16)max_io_size / vdrive->drive.blksize;
     else
         /* default blk_num_max if hardware doesnot advise a proper value */
-        blk_num_max = 8;
+        blk_num_max = 64;
 
     if (op->count <= blk_num_max) {
         virtio_blk_op_one_segment(vdrive, write, sg);