* [PATCH v6 RESEND] io_uring: releasing CPU resources when polling
[not found] <CGME20240709092951epcas5p24783c3bb5c23277cf23a72a6e1855751@epcas5p2.samsung.com>
@ 2024-07-09 9:29 ` hexue
[not found] ` <CGME20240718100113epcas5p255acf51a58cf410d5d0e8cffbca41994@epcas5p2.samsung.com>
2024-07-22 12:31 ` [PATCH v6 RESEND] " Pavel Begunkov
0 siblings, 2 replies; 4+ messages in thread
From: hexue @ 2024-07-09 9:29 UTC (permalink / raw)
To: axboe; +Cc: asml.silence, io-uring, linux-kernel, hexue
io_uring use polling mode could improve the IO performence, but it will
spend 100% of CPU resources to do polling.
This set a signal "IORING_SETUP_HY_POLL" to application, aim to provide
a interface for user to enable a new hybrid polling at io_uring level.
A new hybrid poll is implemented on the io_uring layer. Once IO issued,
it will not polling immediately, but block first and re-run before IO
complete, then poll to reap IO. This poll function could be a suboptimal
solution when running on a single thread, it offers the performance lower
than regular polling but higher than IRQ, and CPU utilization is also lower
than polling.
Test Result
fio-3.35, Gen 4 device
-------------------------------------------------------------------------------------
Performance
-------------------------------------------------------------------------------------
write read randwrite randread
regular poll BW=3939MiB/s BW=6596MiB/s IOPS=190K IOPS=526K
IRQ BW=3927MiB/s BW=6567MiB/s IOPS=181K IOPS=216K
hybrid poll BW=3933MiB/s BW=6600MiB/s IOPS=190K IOPS=390K(suboptimal)
-------------------------------------------------------------------------------------
CPU Utilization
-------------------------------------------------------------------------------------
write read randwrite randread
regular poll 100% 100% 100% 100%
IRQ 38% 53% 100% 100%
hybrid poll 76% 32% 70% 85%
-------------------------------------------------------------------------------------
--
changes since v5:
- Remove cstime recorder
- Use minimize sleep time in different drivers
- Use the half of whole runtime to do schedule
- Consider as a suboptimal solution between
regular poll and IRQ
changes since v4:
- Rewrote the commit
- Update the test results
- Reorganized the code basd on 6.11
changes since v3:
- Simplified the commit
- Add some comments on code
changes since v2:
- Modified some formatting errors
- Move judgement to poll path
changes since v1:
- Extend hybrid poll to async polled io
Signed-off-by: hexue <[email protected]>
---
include/linux/io_uring_types.h | 6 +++
include/uapi/linux/io_uring.h | 1 +
io_uring/io_uring.c | 3 +-
io_uring/rw.c | 74 +++++++++++++++++++++++++++++++++-
4 files changed, 82 insertions(+), 2 deletions(-)
diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index 91224bbcfa73..0897126fb2d7 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -428,6 +428,8 @@ struct io_ring_ctx {
unsigned short n_sqe_pages;
struct page **ring_pages;
struct page **sqe_pages;
+ /* for hybrid poll*/
+ u64 available_time;
};
struct io_tw_state {
@@ -665,6 +667,10 @@ struct io_kiocb {
u64 extra1;
u64 extra2;
} big_cqe;
+ /* for hybrid iopoll */
+ bool poll_state;
+ u64 iopoll_start;
+ u64 iopoll_end;
};
struct io_overflow_cqe {
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 994bf7af0efe..ef32ec319d1f 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -199,6 +199,7 @@ enum io_uring_sqe_flags_bit {
* Removes indirection through the SQ index array.
*/
#define IORING_SETUP_NO_SQARRAY (1U << 16)
+#define IORING_SETUP_HY_POLL (1U << 17)
enum io_uring_op {
IORING_OP_NOP,
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 816e93e7f949..b38f8af118c5 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -299,6 +299,7 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
goto err;
ctx->flags = p->flags;
+ ctx->available_time = LLONG_MAX;
atomic_set(&ctx->cq_wait_nr, IO_CQ_WAKE_INIT);
init_waitqueue_head(&ctx->sqo_sq_wait);
INIT_LIST_HEAD(&ctx->sqd_list);
@@ -3637,7 +3638,7 @@ static long io_uring_setup(u32 entries, struct io_uring_params __user *params)
IORING_SETUP_SQE128 | IORING_SETUP_CQE32 |
IORING_SETUP_SINGLE_ISSUER | IORING_SETUP_DEFER_TASKRUN |
IORING_SETUP_NO_MMAP | IORING_SETUP_REGISTERED_FD_ONLY |
- IORING_SETUP_NO_SQARRAY))
+ IORING_SETUP_NO_SQARRAY | IORING_SETUP_HY_POLL))
return -EINVAL;
return io_uring_create(entries, &p, params);
diff --git a/io_uring/rw.c b/io_uring/rw.c
index 1a2128459cb4..5505f4292ce5 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -772,6 +772,13 @@ static bool need_complete_io(struct io_kiocb *req)
S_ISBLK(file_inode(req->file)->i_mode);
}
+static void init_hybrid_poll(struct io_ring_ctx *ctx, struct io_kiocb *req)
+{
+ /* make sure every req only block once*/
+ req->poll_state = false;
+ req->iopoll_start = ktime_get_ns();
+}
+
static int io_rw_init_file(struct io_kiocb *req, fmode_t mode)
{
struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
@@ -809,6 +816,8 @@ static int io_rw_init_file(struct io_kiocb *req, fmode_t mode)
kiocb->ki_flags |= IOCB_HIPRI;
kiocb->ki_complete = io_complete_rw_iopoll;
req->iopoll_completed = 0;
+ if (ctx->flags & IORING_SETUP_HY_POLL)
+ init_hybrid_poll(ctx, req);
} else {
if (kiocb->ki_flags & IOCB_HIPRI)
return -EINVAL;
@@ -1106,6 +1115,67 @@ void io_rw_fail(struct io_kiocb *req)
io_req_set_res(req, res, req->cqe.flags);
}
+static u64 io_delay(struct io_ring_ctx *ctx, struct io_kiocb *req)
+{
+ struct hrtimer_sleeper timer;
+ enum hrtimer_mode mode;
+ ktime_t kt;
+ u64 sleep_time;
+
+ if (req->poll_state)
+ return 0;
+
+ if (ctx->available_time == LLONG_MAX)
+ return 0;
+
+ /* Using half running time to do schedul */
+ sleep_time = ctx->available_time / 2;
+
+ kt = ktime_set(0, sleep_time);
+ req->poll_state = true;
+
+ mode = HRTIMER_MODE_REL;
+ hrtimer_init_sleeper_on_stack(&timer, CLOCK_MONOTONIC, mode);
+ hrtimer_set_expires(&timer.timer, kt);
+ set_current_state(TASK_INTERRUPTIBLE);
+ hrtimer_sleeper_start_expires(&timer, mode);
+
+ if (timer.task)
+ io_schedule();
+
+ hrtimer_cancel(&timer.timer);
+ __set_current_state(TASK_RUNNING);
+ destroy_hrtimer_on_stack(&timer.timer);
+
+ return sleep_time;
+}
+
+static int io_uring_hybrid_poll(struct io_kiocb *req,
+ struct io_comp_batch *iob, unsigned int poll_flags)
+{
+ struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
+ struct io_ring_ctx *ctx = req->ctx;
+ int ret;
+ u64 runtime, sleep_time;
+
+ sleep_time = io_delay(ctx, req);
+
+ /* it doesn't implement with io_uring passthrough now */
+ ret = req->file->f_op->iopoll(&rw->kiocb, iob, poll_flags);
+
+ req->iopoll_end = ktime_get_ns();
+ runtime = req->iopoll_end - req->iopoll_start - sleep_time;
+ if (runtime < 0)
+ return 0;
+
+ /* use minimize sleep time if there are different speed
+ * drivers, it could get more completions from fast one
+ */
+ if (ctx->available_time > runtime)
+ ctx->available_time = runtime;
+ return ret;
+}
+
int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin)
{
struct io_wq_work_node *pos, *start, *prev;
@@ -1133,7 +1203,9 @@ int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin)
if (READ_ONCE(req->iopoll_completed))
break;
- if (req->opcode == IORING_OP_URING_CMD) {
+ if (ctx->flags & IORING_SETUP_HY_POLL) {
+ ret = io_uring_hybrid_poll(req, &iob, poll_flags);
+ } else if (req->opcode == IORING_OP_URING_CMD) {
struct io_uring_cmd *ioucmd;
ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
--
2.40.1
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