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authorPavel Begunkov <asml.silence@gmail.com>2023-04-06 15:20:08 +0200
committerJens Axboe <axboe@kernel.dk>2023-04-07 00:23:10 +0200
commitd73a572df24661851465c821d33c03e70e4b68e5 (patch)
treec6a218a8fefe4b8505a87989ed5f497ec57310f3 /io_uring
parentio_uring: move pinning out of io_req_local_work_add (diff)
downloadlinux-d73a572df24661851465c821d33c03e70e4b68e5.tar.xz
linux-d73a572df24661851465c821d33c03e70e4b68e5.zip
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>
Diffstat (limited to 'io_uring')
-rw-r--r--io_uring/io_uring.c8
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);
}