Re: [PATCH 3/3] io_uring: don't spinlock when not posting CQEs

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在 2021/9/11 下午9:52, Pavel Begunkov 写道:
When no of queued for the batch completion requests need to post an CQE,
see IOSQE_CQE_SKIP_SUCCESS, avoid grabbing ->completion_lock and other
commit/post.

Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
  fs/io_uring.c | 24 +++++++++++++++---------
  1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 172c857e8b3f..8983a5a6851a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -317,6 +317,7 @@ struct io_submit_state {
bool plug_started;
  	bool			need_plug;
+	bool			flush_cqes;
/*
  	 * Batch completion logic
@@ -1858,6 +1859,8 @@ static void io_req_complete_state(struct io_kiocb *req, long res,
  	req->result = res;
  	req->compl.cflags = cflags;
  	req->flags |= REQ_F_COMPLETE_INLINE;
+	if (!(req->flags & IOSQE_CQE_SKIP_SUCCESS))
Haven't look into this patchset deeply, but this looks
like should be REQ_F_CQE_SKIP ?
+		req->ctx->submit_state.flush_cqes = true;
  }
static inline void __io_req_complete(struct io_kiocb *req, unsigned issue_flags,
@@ -2354,17 +2357,19 @@ static void __io_submit_flush_completions(struct io_ring_ctx *ctx)
  	int i, nr = state->compl_nr;
  	struct req_batch rb;
- spin_lock(&ctx->completion_lock);
-	for (i = 0; i < nr; i++) {
-		struct io_kiocb *req = state->compl_reqs[i];
+	if (state->flush_cqes) {
+		spin_lock(&ctx->completion_lock);
+		for (i = 0; i < nr; i++) {
+			struct io_kiocb *req = state->compl_reqs[i];
- if (!(req->flags & REQ_F_CQE_SKIP))
-			__io_fill_cqe(ctx, req->user_data, req->result,
-				      req->compl.cflags);
+			if (!(req->flags & REQ_F_CQE_SKIP))
+				__io_fill_cqe(ctx, req->user_data, req->result,
+					      req->compl.cflags);
+		}
+		io_commit_cqring(ctx);
+		spin_unlock(&ctx->completion_lock);
+		io_cqring_ev_posted(ctx);
  	}
-	io_commit_cqring(ctx);
-	spin_unlock(&ctx->completion_lock);
-	io_cqring_ev_posted(ctx);
io_init_req_batch(&rb);
  	for (i = 0; i < nr; i++) {
@@ -2376,6 +2381,7 @@ static void __io_submit_flush_completions(struct io_ring_ctx *ctx)
io_req_free_batch_finish(ctx, &rb);
  	state->compl_nr = 0;
+	state->flush_cqes = false;
  }
/*





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