Instead of eagerly running all available local tw, limit the amount of
local tw done to the max of IO_LOCAL_TW_DEFAULT_MAX (20) or wait_nr. The
value of 20 is chosen as a reasonable heuristic to allow enough work
batching but also keep latency down.
Add a retry_llist that maintains a list of local tw that couldn't be
done in time. No synchronisation is needed since it is only modified
within the task context.
Signed-off-by: David Wei <dw@xxxxxxxxxxx>
---
include/linux/io_uring_types.h | 1 +
io_uring/io_uring.c | 43 +++++++++++++++++++++++++---------
io_uring/io_uring.h | 2 +-
3 files changed, 34 insertions(+), 12 deletions(-)
diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index 593c10a02144..011860ade268 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -336,6 +336,7 @@ struct io_ring_ctx {
*/
struct {
struct llist_head work_llist;
+ struct llist_head retry_llist;
unsigned long check_cq;
atomic_t cq_wait_nr;
atomic_t cq_timeouts;
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 83bf041d2648..c3a7d0197636 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -121,6 +121,7 @@
#define IO_COMPL_BATCH 32
#define IO_REQ_ALLOC_BATCH 8
+#define IO_LOCAL_TW_DEFAULT_MAX 20
struct io_defer_entry {
struct list_head list;
@@ -1255,6 +1256,8 @@ static void __cold io_move_task_work_from_local(struct io_ring_ctx *ctx)
struct llist_node *node = llist_del_all(&ctx->work_llist);
__io_fallback_tw(node, false);
+ node = llist_del_all(&ctx->retry_llist);
+ __io_fallback_tw(node, false);
}
static bool io_run_local_work_continue(struct io_ring_ctx *ctx, int events,
@@ -1269,37 +1272,55 @@ static bool io_run_local_work_continue(struct io_ring_ctx *ctx, int events,
return false;
}
+static int __io_run_local_work_loop(struct llist_node **node,
+ struct io_tw_state *ts,
+ int events)
+{
+ while (*node) {
+ struct llist_node *next = (*node)->next;
+ struct io_kiocb *req = container_of(*node, struct io_kiocb,
+ io_task_work.node);
+ INDIRECT_CALL_2(req->io_task_work.func,
+ io_poll_task_func, io_req_rw_complete,
+ req, ts);
+ *node = next;
+ if (--events <= 0)
+ break;
+ }
+
+ return events;
+}
+
static int __io_run_local_work(struct io_ring_ctx *ctx, struct io_tw_state *ts,
int min_events)
{
struct llist_node *node;
unsigned int loops = 0;
- int ret = 0;
+ int ret, limit;
if (WARN_ON_ONCE(ctx->submitter_task != current))
return -EEXIST;
if (ctx->flags & IORING_SETUP_TASKRUN_FLAG)
atomic_andnot(IORING_SQ_TASKRUN, &ctx->rings->sq_flags);
+ limit = max(IO_LOCAL_TW_DEFAULT_MAX, min_events);
again:
+ ret = __io_run_local_work_loop(&ctx->retry_llist.first, ts, limit);
+ if (ctx->retry_llist.first)
+ goto retry_done;
+
/*
* llists are in reverse order, flip it back the right way before
* running the pending items.
*/
node = llist_reverse_order(llist_del_all(&ctx->work_llist));
- while (node) {
- struct llist_node *next = node->next;
- struct io_kiocb *req = container_of(node, struct io_kiocb,
- io_task_work.node);
- INDIRECT_CALL_2(req->io_task_work.func,
- io_poll_task_func, io_req_rw_complete,
- req, ts);
- ret++;
- node = next;
- }
+ ret = __io_run_local_work_loop(&node, ts, ret);
+ ctx->retry_llist.first = node;
loops++;
+ ret = limit - ret;
if (io_run_local_work_continue(ctx, ret, min_events))
goto again;
+retry_done:
io_submit_flush_completions(ctx);
if (io_run_local_work_continue(ctx, ret, min_events))
goto again;
diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index 69eb3b23a5a0..12abee607e4a 100644
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -349,7 +349,7 @@ static inline int io_run_task_work(void)
static inline bool io_local_work_pending(struct io_ring_ctx *ctx)
{
- return !llist_empty(&ctx->work_llist);
+ return !llist_empty(&ctx->work_llist) || !llist_empty(&ctx->retry_llist);
}
static inline bool io_task_work_pending(struct io_ring_ctx *ctx)
--
2.43.5
