Actually there is no upper limitation, so add new module parameter
to provide a way to set a proper max request size for virtio block.
Using a larger request size can improve sequence performance in theory,
and reduce the interaction between guest and hypervisor.
Signed-off-by: Weiping Zhang <zhangweiping@xxxxxxxxxxxxxxx>
---
drivers/block/virtio_blk.c | 32 ++++++++++++++++++++++++++++++--
1 file changed, 30 insertions(+), 2 deletions(-)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 4a07593c..5ac6d59 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -64,6 +64,34 @@ struct virtblk_req {
struct scatterlist sg[];
};
+
+static int max_request_size_set(const char *val, const struct kernel_param *kp);
+
+static const struct kernel_param_ops max_request_size_ops = {
+ .set = max_request_size_set,
+ .get = param_get_uint,
+};
+
+static unsigned long max_request_size = 4096; /* in unit of KiB */
+module_param_cb(max_request_size, &max_request_size_ops, &max_request_size,
+ 0444);
+MODULE_PARM_DESC(max_request_size, "set max request size, in unit of KiB");
+
+static int max_request_size_set(const char *val, const struct kernel_param *kp)
+{
+ int ret;
+ unsigned int size_kb, page_kb = 1 << (PAGE_SHIFT - 10);
+
+ ret = kstrtouint(val, 10, &size_kb);
+ if (ret != 0)
+ return -EINVAL;
+
+ if (size_kb < page_kb)
+ return -EINVAL;
+
+ return param_set_uint(val, kp);
+}
+
static inline blk_status_t virtblk_result(struct virtblk_req *vbr)
{
switch (vbr->status) {
@@ -730,8 +758,8 @@ static int virtblk_probe(struct virtio_device *vdev)
/* We can handle whatever the host told us to handle. */
blk_queue_max_segments(q, vblk->sg_elems-2);
- /* No real sector limit. */
- blk_queue_max_hw_sectors(q, -1U);
+ /* No real sector limit, use 512b (max_request_size << 10) >> 9 */
+ blk_queue_max_hw_sectors_no_limit(q, max_request_size << 1);
/* Host can optionally specify maximum segment size and number of
* segments. */
--
2.9.4
