Batching task work up is an important performance optimisation, as
task_work_add is expensive.
In order to keep the semantics replace the task_list with a fake node
while processing the old list, and then do a cmpxchg at the end to see if
there is more work.
Signed-off-by: Dylan Yudaken <dylany@xxxxxx>
---
io_uring/io_uring.c | 22 +++++++++++++---------
1 file changed, 13 insertions(+), 9 deletions(-)
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index eb29e3f7da5c..19bd7d5ec90c 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -986,11 +986,11 @@ static void ctx_flush_and_put(struct io_ring_ctx *ctx, bool *locked)
percpu_ref_put(&ctx->refs);
}
-
static void handle_tw_list(struct llist_node *node,
- struct io_ring_ctx **ctx, bool *locked)
+ struct io_ring_ctx **ctx, bool *locked,
+ struct llist_node *last)
{
- do {
+ while (node != last) {
struct llist_node *next = node->next;
struct io_kiocb *req = container_of(node, struct io_kiocb,
io_task_work.node);
@@ -1006,7 +1006,7 @@ static void handle_tw_list(struct llist_node *node,
}
req->io_task_work.func(req, locked);
node = next;
- } while (node);
+ }
}
/**
@@ -1045,11 +1045,15 @@ void tctx_task_work(struct callback_head *cb)
struct io_ring_ctx *ctx = NULL;
struct io_uring_task *tctx = container_of(cb, struct io_uring_task,
task_work);
- struct llist_node *node = llist_del_all(&tctx->task_list);
-
- if (node) {
- handle_tw_list(node, &ctx, &uring_locked);
- cond_resched();
+ struct llist_node fake = {};
+ struct llist_node *node = io_llist_xchg(&tctx->task_list, &fake);
+
+ handle_tw_list(node, &ctx, &uring_locked, NULL);
+ node = io_llist_cmpxchg(&tctx->task_list, &fake, NULL);
+ while (node != &fake) {
+ node = io_llist_xchg(&tctx->task_list, &fake);
+ handle_tw_list(node, &ctx, &uring_locked, &fake);
+ node = io_llist_cmpxchg(&tctx->task_list, &fake, NULL);
}
ctx_flush_and_put(ctx, &uring_locked);
--
2.30.2
