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Message-Id: <20241101091957.564220-2-xue01.he@samsung.com>
Date: Fri, 1 Nov 2024 17:19:57 +0800
From: hexue <xue01.he@...sung.com>
To: axboe@...nel.dk, asml.silence@...il.com
Cc: io-uring@...r.kernel.org, linux-kernel@...r.kernel.org, hexue
<xue01.he@...sung.com>
Subject: [PATCH v9 1/1] io_uring: releasing CPU resources when polling
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.
Signed-off-by: hexue <xue01.he@...sung.com>
---
include/linux/io_uring_types.h | 19 ++++++-
include/uapi/linux/io_uring.h | 3 ++
io_uring/io_uring.c | 8 ++-
io_uring/rw.c | 92 ++++++++++++++++++++++++++++++----
4 files changed, 108 insertions(+), 14 deletions(-)
diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index 4b9ba523978d..4a85a823b888 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -302,6 +302,11 @@ struct io_ring_ctx {
* ->uring_cmd() by io_uring_cmd_insert_cancelable()
*/
struct hlist_head cancelable_uring_cmd;
+ /*
+ * For Hybrid IOPOLL, runtime in hybrid polling, without
+ * scheduling time
+ */
+ u64 hybrid_poll_time;
} ____cacheline_aligned_in_smp;
struct {
@@ -447,6 +452,7 @@ enum {
REQ_F_LINK_TIMEOUT_BIT,
REQ_F_NEED_CLEANUP_BIT,
REQ_F_POLLED_BIT,
+ REQ_F_HYBRID_IOPOLL_STATE_BIT,
REQ_F_BUFFER_SELECTED_BIT,
REQ_F_BUFFER_RING_BIT,
REQ_F_REISSUE_BIT,
@@ -506,6 +512,8 @@ enum {
REQ_F_NEED_CLEANUP = IO_REQ_FLAG(REQ_F_NEED_CLEANUP_BIT),
/* already went through poll handler */
REQ_F_POLLED = IO_REQ_FLAG(REQ_F_POLLED_BIT),
+ /* every req only blocks once in hybrid poll */
+ REQ_F_IOPOLL_STATE = IO_REQ_FLAG(REQ_F_HYBRID_IOPOLL_STATE_BIT),
/* buffer already selected */
REQ_F_BUFFER_SELECTED = IO_REQ_FLAG(REQ_F_BUFFER_SELECTED_BIT),
/* buffer selected from ring, needs commit */
@@ -643,8 +651,15 @@ struct io_kiocb {
atomic_t refs;
bool cancel_seq_set;
struct io_task_work io_task_work;
- /* for polled requests, i.e. IORING_OP_POLL_ADD and async armed poll */
- struct hlist_node hash_node;
+ union {
+ /*
+ * for polled requests, i.e. IORING_OP_POLL_ADD and async armed
+ * poll
+ */
+ struct hlist_node hash_node;
+ /* For IOPOLL setup queues, with hybrid polling */
+ u64 iopoll_start;
+ };
/* internal polling, see IORING_FEAT_FAST_POLL */
struct async_poll *apoll;
/* opcode allocated if it needs to store data for async defer */
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index 1fe79e750470..ddd6e42b134d 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -200,6 +200,9 @@ enum io_uring_sqe_flags_bit {
*/
#define IORING_SETUP_NO_SQARRAY (1U << 16)
+/* Use hybrid poll in iopoll process */
+#define IORING_SETUP_HYBRID_IOPOLL (1U << 17)
+
enum io_uring_op {
IORING_OP_NOP,
IORING_OP_READV,
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 4199fbe6ce13..ed131fc824a0 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -301,6 +301,7 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
goto err;
ctx->flags = p->flags;
+ ctx->hybrid_poll_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);
@@ -3545,6 +3546,11 @@ static __cold int io_uring_create(unsigned entries, struct io_uring_params *p,
ctx->clockid = CLOCK_MONOTONIC;
ctx->clock_offset = 0;
+ /* HYBRID_IOPOLL only valid with IOPOLL */
+ if ((ctx->flags & (IORING_SETUP_IOPOLL|IORING_SETUP_HYBRID_IOPOLL)) ==
+ IORING_SETUP_HYBRID_IOPOLL)
+ return -EINVAL;
+
if ((ctx->flags & IORING_SETUP_DEFER_TASKRUN) &&
!(ctx->flags & IORING_SETUP_IOPOLL) &&
!(ctx->flags & IORING_SETUP_SQPOLL))
@@ -3724,7 +3730,7 @@ 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_HYBRID_IOPOLL))
return -EINVAL;
return io_uring_create(entries, &p, params);
diff --git a/io_uring/rw.c b/io_uring/rw.c
index f023ff49c688..340dc4b7b84f 100644
--- a/io_uring/rw.c
+++ b/io_uring/rw.c
@@ -808,6 +808,11 @@ static int io_rw_init_file(struct io_kiocb *req, fmode_t mode, int rw_type)
kiocb->ki_flags |= IOCB_HIPRI;
kiocb->ki_complete = io_complete_rw_iopoll;
req->iopoll_completed = 0;
+ if (ctx->flags & IORING_SETUP_HYBRID_IOPOLL) {
+ /* make sure every req only blocks once*/
+ req->flags &= ~REQ_F_IOPOLL_STATE;
+ req->iopoll_start = ktime_get_ns();
+ }
} else {
if (kiocb->ki_flags & IOCB_HIPRI)
return -EINVAL;
@@ -1112,6 +1117,78 @@ void io_rw_fail(struct io_kiocb *req)
io_req_set_res(req, res, req->cqe.flags);
}
+static int io_uring_classic_poll(struct io_kiocb *req, struct io_comp_batch *iob,
+ unsigned int poll_flags)
+{
+ struct file *file = req->file;
+
+ if (req->opcode == IORING_OP_URING_CMD) {
+ struct io_uring_cmd *ioucmd;
+
+ ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
+ return file->f_op->uring_cmd_iopoll(ioucmd, iob, poll_flags);
+ } else {
+ struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
+
+ return file->f_op->iopoll(&rw->kiocb, iob, poll_flags);
+ }
+}
+
+static u64 io_hybrid_iopoll_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->flags & REQ_F_IOPOLL_STATE)
+ return 0;
+
+ if (ctx->hybrid_poll_time == LLONG_MAX)
+ return 0;
+
+ /* Using half the running time to do schedule */
+ sleep_time = ctx->hybrid_poll_time / 2;
+
+ kt = ktime_set(0, sleep_time);
+ req->flags |= REQ_F_IOPOLL_STATE;
+
+ 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_ring_ctx *ctx = req->ctx;
+ u64 runtime, sleep_time;
+ int ret;
+
+ sleep_time = io_hybrid_iopoll_delay(ctx, req);
+ ret = io_uring_classic_poll(req, iob, poll_flags);
+ runtime = ktime_get_ns() - req->iopoll_start - sleep_time;
+
+ /*
+ * Use minimum sleep time if we're polling devices with different
+ * latencies. We could get more completions from the faster ones.
+ */
+ if (ctx->hybrid_poll_time > runtime)
+ ctx->hybrid_poll_time = runtime;
+
+ return ret;
+}
+
int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin)
{
struct io_wq_work_node *pos, *start, *prev;
@@ -1128,7 +1205,6 @@ int io_do_iopoll(struct io_ring_ctx *ctx, bool force_nonspin)
wq_list_for_each(pos, start, &ctx->iopoll_list) {
struct io_kiocb *req = container_of(pos, struct io_kiocb, comp_list);
- struct file *file = req->file;
int ret;
/*
@@ -1139,17 +1215,11 @@ 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) {
- struct io_uring_cmd *ioucmd;
-
- ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
- ret = file->f_op->uring_cmd_iopoll(ioucmd, &iob,
- poll_flags);
- } else {
- struct io_rw *rw = io_kiocb_to_cmd(req, struct io_rw);
+ if (ctx->flags & IORING_SETUP_HYBRID_IOPOLL)
+ ret = io_uring_hybrid_poll(req, &iob, poll_flags);
+ else
+ ret = io_uring_classic_poll(req, &iob, poll_flags);
- ret = file->f_op->iopoll(&rw->kiocb, &iob, poll_flags);
- }
if (unlikely(ret < 0))
return ret;
else if (ret)
--
2.40.1
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