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| author | Pavel Begunkov <asml.silence@gmail.com> | 2023-04-06 16:20:08 +0300 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2023-04-07 01:23:10 +0300 |
| commit | d73a572df24661851465c821d33c03e70e4b68e5 (patch) | |
| tree | c6a218a8fefe4b8505a87989ed5f497ec57310f3 | |
| parent | ab1c590f5c9b96d8d8843d351aed72469f8f2ef0 (diff) | |
| download | linux-d73a572df24661851465c821d33c03e70e4b68e5.tar.xz | |
io_uring: optimize local tw add ctx pinning
We currently pin the ctx for io_req_local_work_add() with
percpu_ref_get/put, which implies two rcu_read_lock/unlock pairs and some
extra overhead on top in the fast path. Replace it with a pure rcu read
and let io_ring_exit_work() synchronise against it.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/cbdfcb6b232627f30e9e50ef91f13c4f05910247.1680782017.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | io_uring/io_uring.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 29a0516ee5ce..fb7215b543cd 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -1332,9 +1332,9 @@ void __io_req_task_work_add(struct io_kiocb *req, bool allow_local) struct io_ring_ctx *ctx = req->ctx; if (allow_local && ctx->flags & IORING_SETUP_DEFER_TASKRUN) { - percpu_ref_get(&ctx->refs); + rcu_read_lock(); io_req_local_work_add(req); - percpu_ref_put(&ctx->refs); + rcu_read_unlock(); return; } @@ -3052,6 +3052,10 @@ static __cold void io_ring_exit_work(struct work_struct *work) spin_lock(&ctx->completion_lock); spin_unlock(&ctx->completion_lock); + /* pairs with RCU read section in io_req_local_work_add() */ + if (ctx->flags & IORING_SETUP_DEFER_TASKRUN) + synchronize_rcu(); + io_ring_ctx_free(ctx); } |