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authorPavel Begunkov <asml.silence@gmail.com>2023-01-09 17:46:13 +0300
committerJens Axboe <axboe@kernel.dk>2023-01-30 01:17:40 +0300
commitc3f4d39ee4bc06f975ff45012398342ff276eb69 (patch)
treec9b87d65bcfa0cfb1161e63468cbe3de2b125c49 /io_uring/io_uring.c
parentd80c0f00d04766972c95e72b7535a842d6f4680d (diff)
downloadlinux-c3f4d39ee4bc06f975ff45012398342ff276eb69.tar.xz
io_uring: optimise deferred tw execution
We needed fake nodes in __io_run_local_work() and to avoid unecessary wake ups while the task already running task_works, but we don't need them anymore since wake ups are protected by cq_waiting, which is always cleared by the time we're executing deferred task_work items. Note that because of loose sync around cq_waiting clearing io_req_local_work_add() may wake the task more than once, but that's fine and should be rare to not hurt perf. Signed-off-by: Pavel Begunkov <asml.silence@gmail.com> Link: https://lore.kernel.org/r/8839534891f0a2f1076e78554a31ea7e099f7de5.1673274244.git.asml.silence@gmail.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'io_uring/io_uring.c')
-rw-r--r--io_uring/io_uring.c24
1 files changed, 7 insertions, 17 deletions
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 3f92028a7ee8..653361746203 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -1322,17 +1322,16 @@ static void __cold io_move_task_work_from_local(struct io_ring_ctx *ctx)
static int __io_run_local_work(struct io_ring_ctx *ctx, bool *locked)
{
struct llist_node *node;
- struct llist_node fake;
- struct llist_node *current_final = NULL;
+ unsigned int loops = 0;
int ret = 0;
- unsigned int loops = 1;
if (WARN_ON_ONCE(ctx->submitter_task != current))
return -EEXIST;
-
- node = io_llist_xchg(&ctx->work_llist, &fake);
+ if (ctx->flags & IORING_SETUP_TASKRUN_FLAG)
+ atomic_andnot(IORING_SQ_TASKRUN, &ctx->rings->sq_flags);
again:
- while (node != current_final) {
+ node = io_llist_xchg(&ctx->work_llist, NULL);
+ while (node) {
struct llist_node *next = node->next;
struct io_kiocb *req = container_of(node, struct io_kiocb,
io_task_work.node);
@@ -1341,23 +1340,14 @@ again:
ret++;
node = next;
}
+ loops++;
- if (ctx->flags & IORING_SETUP_TASKRUN_FLAG)
- atomic_andnot(IORING_SQ_TASKRUN, &ctx->rings->sq_flags);
-
- node = io_llist_cmpxchg(&ctx->work_llist, &fake, NULL);
- if (node != &fake) {
- loops++;
- current_final = &fake;
- node = io_llist_xchg(&ctx->work_llist, &fake);
+ if (!llist_empty(&ctx->work_llist))
goto again;
- }
-
if (*locked)
io_submit_flush_completions(ctx);
trace_io_uring_local_work_run(ctx, ret, loops);
return ret;
-
}
static inline int io_run_local_work_locked(struct io_ring_ctx *ctx)