The current logic of requests with IOSQE_FORCE_ASYNC is first queueing
it to io-worker, then execute it in a synchronous way. For unbound works
like pollable requests(e.g. read/write a socketfd), the io-worker may
stuck there waiting for events for a long time. And thus other works
wait in the list for a long time too.
Let's introduce a new sqe flag IOSQE_ASYNC_HIBRID for unbound works
(currently pollable requests), with this a request will first be queued
to io-worker, then executed in a nonblock try rather than a synchronous
way. Failure of that leads it to arm poll stuff and then the worker can
begin to handle other works.
Suggested-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Hao Xu <haoxu@xxxxxxxxxxxxxxxxx>
---
fs/io_uring.c | 6 +++++-
include/uapi/linux/io_uring.h | 4 +++-
2 files changed, 8 insertions(+), 2 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 73135c5c6168..a99f7f46e6d4 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -104,7 +104,8 @@
#define IORING_MAX_REG_BUFFERS (1U << 14)
#define SQE_COMMON_FLAGS (IOSQE_FIXED_FILE | IOSQE_IO_LINK | \
- IOSQE_IO_HARDLINK | IOSQE_ASYNC)
+ IOSQE_IO_HARDLINK | IOSQE_ASYNC | \
+ IOSQE_ASYNC_HYBRID)
#define SQE_VALID_FLAGS (SQE_COMMON_FLAGS|IOSQE_BUFFER_SELECT|IOSQE_IO_DRAIN)
@@ -709,6 +710,7 @@ enum {
REQ_F_HARDLINK_BIT = IOSQE_IO_HARDLINK_BIT,
REQ_F_FORCE_ASYNC_BIT = IOSQE_ASYNC_BIT,
REQ_F_BUFFER_SELECT_BIT = IOSQE_BUFFER_SELECT_BIT,
+ REQ_F_ASYNC_HYBRID_BIT = IOSQE_ASYNC_HYBRID_BIT,
/* first byte is taken by user flags, shift it to not overlap */
REQ_F_FAIL_BIT = 8,
@@ -747,6 +749,8 @@ enum {
REQ_F_FORCE_ASYNC = BIT(REQ_F_FORCE_ASYNC_BIT),
/* IOSQE_BUFFER_SELECT */
REQ_F_BUFFER_SELECT = BIT(REQ_F_BUFFER_SELECT_BIT),
+ /* IOSQE_ASYNC_HYBRID */
+ REQ_F_ASYNC_HYBRID = BIT(REQ_F_ASYNC_HYBRID_BIT),
/* fail rest of links */
REQ_F_FAIL = BIT(REQ_F_FAIL_BIT),
diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h
index c45b5e9a9387..3e49a7dbe636 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -70,6 +70,7 @@ enum {
IOSQE_IO_HARDLINK_BIT,
IOSQE_ASYNC_BIT,
IOSQE_BUFFER_SELECT_BIT,
+ IOSQE_ASYNC_HYBRID_BIT,
};
/*
@@ -87,7 +88,8 @@ enum {
#define IOSQE_ASYNC (1U << IOSQE_ASYNC_BIT)
/* select buffer from sqe->buf_group */
#define IOSQE_BUFFER_SELECT (1U << IOSQE_BUFFER_SELECT_BIT)
-
+/* first force async then arm poll */
+#define IOSQE_ASYNC_HYBRID (1U << IOSQE_ASYNC_HYBRID_BIT)
/*
* io_uring_setup() flags
*/
--
2.24.4
