block/rnbd-clt: Support polling mode for IO latency optimization
RNBD can make double-queues for irq-mode and poll-mode.
For example, on 4-CPU system 8 request-queues are created,
4 for irq-mode and 4 for poll-mode.
If the IO has HIPRI flag, the block-layer will call .poll function
of RNBD. Then IO is sent to the poll-mode queue.
Add optional nr_poll_queues argument for map_devices interface.
To support polling of RNBD, RTRS client creates connections
for both of irq-mode and direct-poll-mode.
For example, on 4-CPU system it could've create 5 connections:
con[0] => user message (softirq cq)
con[1:4] => softirq cq
After this patch, it can create 9 connections:
con[0] => user message (softirq cq)
con[1:4] => softirq cq
con[5:8] => DIRECT-POLL cq
Cc: Leon Romanovsky <leonro@nvidia.com>
Cc: linux-rdma@vger.kernel.org
Signed-off-by: Gioh Kim <gi-oh.kim@ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Acked-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Link: https://lore.kernel.org/r/20210419073722.15351-14-gi-oh.kim@ionos.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/block/rnbd/rnbd-clt.h b/drivers/block/rnbd/rnbd-clt.h
index 714d426..451e738 100644
--- a/drivers/block/rnbd/rnbd-clt.h
+++ b/drivers/block/rnbd/rnbd-clt.h
@@ -90,6 +90,7 @@ struct rnbd_clt_session {
int queue_depth;
u32 max_io_size;
struct blk_mq_tag_set tag_set;
+ u32 nr_poll_queues;
struct mutex lock; /* protects state and devs_list */
struct list_head devs_list; /* list of struct rnbd_clt_dev */
refcount_t refcount;
@@ -118,6 +119,7 @@ struct rnbd_clt_dev {
enum rnbd_clt_dev_state dev_state;
char *pathname;
enum rnbd_access_mode access_mode;
+ u32 nr_poll_queues;
bool read_only;
bool rotational;
bool wc;
@@ -147,7 +149,8 @@ struct rnbd_clt_dev *rnbd_clt_map_device(const char *sessname,
struct rtrs_addr *paths,
size_t path_cnt, u16 port_nr,
const char *pathname,
- enum rnbd_access_mode access_mode);
+ enum rnbd_access_mode access_mode,
+ u32 nr_poll_queues);
int rnbd_clt_unmap_device(struct rnbd_clt_dev *dev, bool force,
const struct attribute *sysfs_self);