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 <[email protected]> --- 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
