Commit 86f0348a authored by Sagi Grimberg's avatar Sagi Grimberg Committed by Christoph Hellwig
Browse files

nvme-tcp: leverage request plugging 



blk-mq request plugging can improve the execution of our pipeline.
When we queue a request we actually trigger our I/O worker thread
yielding a context switch by definition. However if we know that
there are more requests in the pipe that are coming, we are better
off not trigger our I/O worker and only do that for the last request
in the batch (bd->last). By having it, we improve efficiency by
amortizing context switches over a batch of requests.

Signed-off-by: default avatarSagi Grimberg <sagi@grimberg.me>
Tested-by: default avatarMark Wunderlich <mark.wunderlich@intel.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent 15ec928a

drivers/nvme/host/tcp.c

+14 −5
Original line number Diff line number Diff line
@@ -262,7 +262,7 @@ static inline void nvme_tcp_advance_req(struct nvme_tcp_request *req, 
}



static inline void nvme_tcp_queue_request(struct nvme_tcp_request *req,

		bool sync)

		bool sync, bool last)

{

	struct nvme_tcp_queue *queue = req->queue;

	bool empty;
@@ -279,7 +279,7 @@ static inline void nvme_tcp_queue_request(struct nvme_tcp_request *req, 
	    sync && empty && mutex_trylock(&queue->send_mutex)) {

		nvme_tcp_try_send(queue);

		mutex_unlock(&queue->send_mutex);

	} else {

	} else if (last) {

		queue_work_on(queue->io_cpu, nvme_tcp_wq, &queue->io_work);

	}

}
@@ -610,7 +610,7 @@ static int nvme_tcp_handle_r2t(struct nvme_tcp_queue *queue, 
	req->state = NVME_TCP_SEND_H2C_PDU;

	req->offset = 0;



	nvme_tcp_queue_request(req, false);

	nvme_tcp_queue_request(req, false, true);



	return 0;

}
@@ -2120,7 +2120,7 @@ static void nvme_tcp_submit_async_event(struct nvme_ctrl *arg) 
	ctrl->async_req.curr_bio = NULL;

	ctrl->async_req.data_len = 0;



	nvme_tcp_queue_request(&ctrl->async_req, true);

	nvme_tcp_queue_request(&ctrl->async_req, true, true);

}



static enum blk_eh_timer_return
@@ -2232,6 +2232,14 @@ static blk_status_t nvme_tcp_setup_cmd_pdu(struct nvme_ns *ns, 
	return 0;

}



static void nvme_tcp_commit_rqs(struct blk_mq_hw_ctx *hctx)

{

	struct nvme_tcp_queue *queue = hctx->driver_data;



	if (!llist_empty(&queue->req_list))

		queue_work_on(queue->io_cpu, nvme_tcp_wq, &queue->io_work);

}



static blk_status_t nvme_tcp_queue_rq(struct blk_mq_hw_ctx *hctx,

		const struct blk_mq_queue_data *bd)

{
@@ -2251,7 +2259,7 @@ static blk_status_t nvme_tcp_queue_rq(struct blk_mq_hw_ctx *hctx, 


	blk_mq_start_request(rq);



	nvme_tcp_queue_request(req, true);

	nvme_tcp_queue_request(req, true, bd->last);



	return BLK_STS_OK;

}
@@ -2319,6 +2327,7 @@ static int nvme_tcp_poll(struct blk_mq_hw_ctx *hctx) 


static const struct blk_mq_ops nvme_tcp_mq_ops = {

	.queue_rq	= nvme_tcp_queue_rq,

	.commit_rqs	= nvme_tcp_commit_rqs,

	.complete	= nvme_complete_rq,

	.init_request	= nvme_tcp_init_request,

	.exit_request	= nvme_tcp_exit_request,