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authorPavel Begunkov <asml.silence@gmail.com>2023-04-06 14:20:12 +0100
committerJens Axboe <axboe@kernel.dk>2023-04-06 16:23:28 -0600
commit8751d15426a31baaf40f7570263c27c3e5d1dc44 (patch)
treece78034f5b032052374c63e97c403143511365a2 /io_uring/io_uring.h
parent5150940079a3ce94d7474f6f5b0d6276569dc1de (diff)
io_uring: reduce scheduling due to tw
Every task_work will try to wake the task to be executed, which causes excessive scheduling and additional overhead. For some tw it's justified, but others won't do much but post a single CQE. When a task waits for multiple cqes, every such task_work will wake it up. Instead, the task may give a hint about how many cqes it waits for, io_req_local_work_add() will compare against it and skip wake ups if #cqes + #tw is not enough to satisfy the waiting condition. Task_work that uses the optimisation should be simple enough and never post more than one CQE. It's also ignored for non DEFER_TASKRUN rings. Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Link: https://lore.kernel.org/r/d2b77e99d1e86624d8a69f7037d764b739dcd225.1680782017.git.asml.silence@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'io_uring/io_uring.h')
-rw-r--r--io_uring/io_uring.h9
1 files changed, 9 insertions, 0 deletions
diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index cb4309a2acdc..ef449e43d493 100644
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -18,6 +18,15 @@
enum {
/* don't use deferred task_work */
IOU_F_TWQ_FORCE_NORMAL = 1,
+
+ /*
+ * A hint to not wake right away but delay until there are enough of
+ * tw's queued to match the number of CQEs the task is waiting for.
+ *
+ * Must not be used wirh requests generating more than one CQE.
+ * It's also ignored unless IORING_SETUP_DEFER_TASKRUN is set.
+ */
+ IOU_F_TWQ_LAZY_WAKE = 2,
};
enum {