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nvme-tcp: avoid scheduling io_work if we are already polling

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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: 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>
This commit is contained in:
Sagi Grimberg 2020-05-01 14:25:44 -07:00 committed by Jens Axboe
parent 386e5e6e1a
commit 72e5d757c6
1 changed files with 5 additions and 1 deletions
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6
drivers/nvme/host/tcp.c
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@ -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;
}