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Message-Id: <20220713140711.97356-3-ming.lei@redhat.com>
Date: Wed, 13 Jul 2022 22:07:11 +0800
From: Ming Lei <ming.lei@...hat.com>
To: Jens Axboe <axboe@...nel.dk>
Cc: linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
io-uring@...r.kernel.org,
Gabriel Krisman Bertazi <krisman@...labora.com>,
ZiyangZhang <ZiyangZhang@...ux.alibaba.com>,
Xiaoguang Wang <xiaoguang.wang@...ux.alibaba.com>,
Ming Lei <ming.lei@...hat.com>
Subject: [PATCH V5 2/2] ublk_drv: support to complete io command via task_work_add
Use task_work_add if it is available, since task_work_add can bring
up better performance, especially batching signaling ->ubq_daemon can
be done.
It is observed that task_work_add() can boost iops by +4% on random
4k io test. Also except for completing io command, all other code
paths are same with completing io command via
io_uring_cmd_complete_in_task.
Meantime add one flag of UBLK_F_URING_CMD_COMP_IN_TASK for comparing
the mode easily.
Signed-off-by: Ming Lei <ming.lei@...hat.com>
---
drivers/block/ublk_drv.c | 75 +++++++++++++++++++++++++++++++----
include/uapi/linux/ublk_cmd.h | 6 +++
2 files changed, 73 insertions(+), 8 deletions(-)
diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 922a84c86fc6..35fa06ee70ff 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -41,10 +41,15 @@
#include <linux/delay.h>
#include <linux/mm.h>
#include <asm/page.h>
+#include <linux/task_work.h>
#include <uapi/linux/ublk_cmd.h>
#define UBLK_MINORS (1U << MINORBITS)
+struct ublk_rq_data {
+ struct callback_head work;
+};
+
struct ublk_uring_cmd_pdu {
struct request *req;
};
@@ -91,6 +96,7 @@ struct ublk_queue {
int q_id;
int q_depth;
+ unsigned long flags;
struct task_struct *ubq_daemon;
char *io_cmd_buf;
@@ -149,6 +155,14 @@ static DEFINE_MUTEX(ublk_ctl_mutex);
static struct miscdevice ublk_misc;
+static inline bool ublk_can_use_task_work(const struct ublk_queue *ubq)
+{
+ if (IS_BUILTIN(CONFIG_BLK_DEV_UBLK) &&
+ !(ubq->flags & UBLK_F_URING_CMD_COMP_IN_TASK))
+ return true;
+ return false;
+}
+
static struct ublk_device *ublk_get_device(struct ublk_device *ub)
{
if (kobject_get_unless_zero(&ub->cdev_dev.kobj))
@@ -500,12 +514,10 @@ static void __ublk_fail_req(struct ublk_io *io, struct request *req)
#define UBLK_REQUEUE_DELAY_MS 3
-static void ublk_rq_task_work_cb(struct io_uring_cmd *cmd)
+static inline void __ublk_rq_task_work(struct request *req)
{
- struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
- struct ublk_device *ub = cmd->file->private_data;
- struct request *req = pdu->req;
struct ublk_queue *ubq = req->mq_hctx->driver_data;
+ struct ublk_device *ub = ubq->dev;
int tag = req->tag;
struct ublk_io *io = &ubq->ios[tag];
bool task_exiting = current != ubq->ubq_daemon ||
@@ -557,13 +569,27 @@ static void ublk_rq_task_work_cb(struct io_uring_cmd *cmd)
io_uring_cmd_done(io->cmd, UBLK_IO_RES_OK, 0);
}
+static void ublk_rq_task_work_cb(struct io_uring_cmd *cmd)
+{
+ struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
+
+ __ublk_rq_task_work(pdu->req);
+}
+
+static void ublk_rq_task_work_fn(struct callback_head *work)
+{
+ struct ublk_rq_data *data = container_of(work,
+ struct ublk_rq_data, work);
+ struct request *req = blk_mq_rq_from_pdu(data);
+
+ __ublk_rq_task_work(req);
+}
+
static blk_status_t ublk_queue_rq(struct blk_mq_hw_ctx *hctx,
const struct blk_mq_queue_data *bd)
{
struct ublk_queue *ubq = hctx->driver_data;
struct request *rq = bd->rq;
- struct io_uring_cmd *cmd = ubq->ios[rq->tag].cmd;
- struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
blk_status_t res;
/* fill iod to slot in io cmd buffer */
@@ -574,16 +600,36 @@ static blk_status_t ublk_queue_rq(struct blk_mq_hw_ctx *hctx,
blk_mq_start_request(bd->rq);
if (unlikely(ubq_daemon_is_dying(ubq))) {
+ fail:
mod_delayed_work(system_wq, &ubq->dev->monitor_work, 0);
return BLK_STS_IOERR;
}
- pdu->req = rq;
- io_uring_cmd_complete_in_task(cmd, ublk_rq_task_work_cb);
+ if (ublk_can_use_task_work(ubq)) {
+ struct ublk_rq_data *data = blk_mq_rq_to_pdu(rq);
+ enum task_work_notify_mode notify_mode = bd->last ?
+ TWA_SIGNAL_NO_IPI : TWA_NONE;
+
+ if (task_work_add(ubq->ubq_daemon, &data->work, notify_mode))
+ goto fail;
+ } else {
+ struct io_uring_cmd *cmd = ubq->ios[rq->tag].cmd;
+ struct ublk_uring_cmd_pdu *pdu = ublk_get_uring_cmd_pdu(cmd);
+
+ pdu->req = rq;
+ io_uring_cmd_complete_in_task(cmd, ublk_rq_task_work_cb);
+ }
return BLK_STS_OK;
}
+static void ublk_commit_rqs(struct blk_mq_hw_ctx *hctx)
+{
+ struct ublk_queue *ubq = hctx->driver_data;
+
+ if (ublk_can_use_task_work(ubq))
+ __set_notify_signal(ubq->ubq_daemon);
+}
static int ublk_init_hctx(struct blk_mq_hw_ctx *hctx, void *driver_data,
unsigned int hctx_idx)
@@ -595,9 +641,20 @@ static int ublk_init_hctx(struct blk_mq_hw_ctx *hctx, void *driver_data,
return 0;
}
+static int ublk_init_rq(struct blk_mq_tag_set *set, struct request *req,
+ unsigned int hctx_idx, unsigned int numa_node)
+{
+ struct ublk_rq_data *data = blk_mq_rq_to_pdu(req);
+
+ init_task_work(&data->work, ublk_rq_task_work_fn);
+ return 0;
+}
+
static const struct blk_mq_ops ublk_mq_ops = {
.queue_rq = ublk_queue_rq,
+ .commit_rqs = ublk_commit_rqs,
.init_hctx = ublk_init_hctx,
+ .init_request = ublk_init_rq,
};
static int ublk_ch_open(struct inode *inode, struct file *filp)
@@ -912,6 +969,7 @@ static int ublk_init_queue(struct ublk_device *ub, int q_id)
void *ptr;
int size;
+ ubq->flags = ub->dev_info.flags[0];
ubq->q_id = q_id;
ubq->q_depth = ub->dev_info.queue_depth;
size = ublk_queue_cmd_buf_size(ub, q_id);
@@ -1099,6 +1157,7 @@ static int ublk_add_dev(struct ublk_device *ub)
ub->tag_set.nr_hw_queues = ub->dev_info.nr_hw_queues;
ub->tag_set.queue_depth = ub->dev_info.queue_depth;
ub->tag_set.numa_node = NUMA_NO_NODE;
+ ub->tag_set.cmd_size = sizeof(struct ublk_rq_data);
ub->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
ub->tag_set.driver_data = ub;
diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
index 4f0c16ec875e..a3f5e7c21807 100644
--- a/include/uapi/linux/ublk_cmd.h
+++ b/include/uapi/linux/ublk_cmd.h
@@ -48,6 +48,12 @@
*/
#define UBLK_F_SUPPORT_ZERO_COPY (1UL << 0)
+/*
+ * Force to complete io cmd via io_uring_cmd_complete_in_task so that
+ * performance comparison is done easily with using task_work_add
+ */
+#define UBLK_F_URING_CMD_COMP_IN_TASK (1UL << 1)
+
/* device state */
#define UBLK_S_DEV_DEAD 0
#define UBLK_S_DEV_LIVE 1
--
2.31.1
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