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[188.28.229.101]) by smtp.gmail.com with ESMTPSA id m1-20020a7bca41000000b003d1de805de5sm39967839wml.16.2023.01.02.19.05.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 02 Jan 2023 19:05:28 -0800 (PST) From: Pavel Begunkov To: io-uring@vger.kernel.org Cc: Jens Axboe , asml.silence@gmail.com Subject: [RFC v2 12/13] io_uring: waitqueue-less cq waiting Date: Tue, 3 Jan 2023 03:04:03 +0000 Message-Id: <304db555100334593675eba81fd07f95d7ec02f5.1672713341.git.asml.silence@gmail.com> X-Mailer: git-send-email 2.38.1 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org With DEFER_TASKRUN only ctx->submitter_task might be waiting for CQEs, we can use this to optimise io_cqring_wait(). Replace ->cq_wait waitqueue with waking the task directly. It works but misses an important optimisation covered by the following patch, so this patch without follow ups might hurt performance. Signed-off-by: Pavel Begunkov --- io_uring/io_uring.c | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 98d0d9e49be0..943032d2fd21 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -1273,7 +1273,12 @@ static void io_req_local_work_add(struct io_kiocb *req) if (ctx->has_evfd) io_eventfd_signal(ctx); - __io_cqring_wake(ctx); + + if (ctx->flags & IORING_SETUP_DEFER_TASKRUN) { + wake_up_state(ctx->submitter_task, TASK_INTERRUPTIBLE); + } else { + __io_cqring_wake(ctx); + } } void __io_req_task_work_add(struct io_kiocb *req, bool allow_local) @@ -2558,12 +2563,17 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, do { unsigned long check_cq; - prepare_to_wait_exclusive(&ctx->cq_wait, &iowq.wq, - TASK_INTERRUPTIBLE); + if (ctx->flags & IORING_SETUP_DEFER_TASKRUN) { + set_current_state(TASK_INTERRUPTIBLE); + } else { + prepare_to_wait_exclusive(&ctx->cq_wait, &iowq.wq, + TASK_INTERRUPTIBLE); + } + ret = io_cqring_wait_schedule(ctx, &iowq, timeout); + __set_current_state(TASK_RUNNING); if (ret < 0) break; - __set_current_state(TASK_RUNNING); /* * Run task_work after scheduling and before io_should_wake(). * If we got woken because of task_work being processed, run it @@ -2591,7 +2601,8 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, cond_resched(); } while (1); - finish_wait(&ctx->cq_wait, &iowq.wq); + if (!(ctx->flags & IORING_SETUP_DEFER_TASKRUN)) + finish_wait(&ctx->cq_wait, &iowq.wq); restore_saved_sigmask_unless(ret == -EINTR); return READ_ONCE(rings->cq.head) == READ_ONCE(rings->cq.tail) ? ret : 0; -- 2.38.1