nvme-tcp: avoid scheduling io_work if we are already polling (72e5d757) · Commits · 戴 / test

When the user runs polled I/O, we shouldn't have to trigger the workqueue to generate the receive work upon the .data_ready upcall. This prevents a redundant context switch when the application is already polling for completions. Proposed-by:

Mark Wunderlich <mark.wunderlich@intel.com> Signed-off-by:

Sagi Grimberg <sagi@grimberg.me> Signed-off-by:

Christoph Hellwig <hch@lst.de> Signed-off-by:

Jens Axboe <axboe@kernel.dk>

drivers/nvme/host/tcp.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -60,6 +60,7 @@ struct nvme_tcp_request {
		enum nvme_tcp_queue_flags {
		NVME_TCP_Q_ALLOCATED = 0,
		NVME_TCP_Q_LIVE = 1,
		NVME_TCP_Q_POLLING = 2,
		};

		enum nvme_tcp_recv_state {
		@@ -796,7 +797,8 @@ static void nvme_tcp_data_ready(struct sock *sk)

		read_lock_bh(&sk->sk_callback_lock);
		queue = sk->sk_user_data;
		if (likely(queue && queue->rd_enabled))
		if (likely(queue && queue->rd_enabled) &&
		!test_bit(NVME_TCP_Q_POLLING, &queue->flags))
		queue_work_on(queue->io_cpu, nvme_tcp_wq, &queue->io_work);
		read_unlock_bh(&sk->sk_callback_lock);
		}
		@@ -2302,9 +2304,11 @@ static int nvme_tcp_poll(struct blk_mq_hw_ctx *hctx)
		if (!test_bit(NVME_TCP_Q_LIVE, &queue->flags))
		return 0;

		set_bit(NVME_TCP_Q_POLLING, &queue->flags);
		if (sk_can_busy_loop(sk) && skb_queue_empty_lockless(&sk->sk_receive_queue))
		sk_busy_loop(sk, true);
		nvme_tcp_try_recv(queue);
		clear_bit(NVME_TCP_Q_POLLING, &queue->flags);
		return queue->nr_cqe;
		}

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