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From: Dylan Yudaken <[email protected]>
To: <[email protected]>, <[email protected]>, <[email protected]>
Cc: <[email protected]>, Dylan Yudaken <[email protected]>
Subject: [PATCH v2 for-next 5/8] io_uring: batch task_work
Date: Wed, 22 Jun 2022 06:40:25 -0700	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

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 <[email protected]>
---
 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


  parent reply	other threads:[~2022-06-22 13:40 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-22 13:40 [PATCH v2 for-next 0/8] io_uring: tw contention improvments Dylan Yudaken
2022-06-22 13:40 ` [PATCH v2 for-next 1/8] io_uring: remove priority tw list optimisation Dylan Yudaken
2022-06-22 13:40 ` [PATCH v2 for-next 2/8] io_uring: remove __io_req_task_work_add Dylan Yudaken
2022-06-22 13:40 ` [PATCH v2 for-next 3/8] io_uring: lockless task list Dylan Yudaken
2022-06-22 13:40 ` [PATCH v2 for-next 4/8] io_uring: introduce llist helpers Dylan Yudaken
2022-06-22 13:40 ` Dylan Yudaken [this message]
2022-06-22 13:40 ` [PATCH v2 for-next 6/8] io_uring: move io_uring_get_opcode out of TP_printk Dylan Yudaken
2022-06-22 13:40 ` [PATCH v2 for-next 7/8] io_uring: add trace event for running task work Dylan Yudaken
2022-06-22 13:40 ` [PATCH v2 for-next 8/8] io_uring: trace task_work_run Dylan Yudaken
2022-06-22 15:21 ` [PATCH v2 for-next 0/8] io_uring: tw contention improvments Jens Axboe
2022-06-23  8:23   ` Hao Xu
2022-06-22 17:39 ` Jens Axboe

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