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nvme-tcp: leverage request plugging

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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: Sagi Grimberg <sagi@grimberg.me>
Tested-by: Mark Wunderlich <mark.wunderlich@intel.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Sagi Grimberg 2020-06-18 17:30:23 -07:00 committed by Christoph Hellwig
parent 15ec928a65
commit 86f0348ace
1 changed files with 14 additions and 5 deletions
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19
drivers/nvme/host/tcp.c
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@ -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,