Commit 40510a63 authored by Sagi Grimberg's avatar Sagi Grimberg Committed by Keith Busch
Browse files

nvme-tcp: optimize queue io_cpu assignment for multiple queue maps 



Currently, queue io_cpu assignment is done sequentially for default,
read and poll queues based on queue id. This causes miss-alignment between
context of CPU initiating I/O and the I/O worker thread processing
queued requests or completions.

Change to modify queue io_cpu assignment to take into account queue
maps offset. Each queue io_cpu will start at zero for each queue map.
This essentially aligns read/poll queues to start over the same range as
default queues.

Testing performed by Mark with:
- ram device (nvmet)
- single CPU core (pinned)
- 100% 4k reads
- engine io_uring (not using sq_thread option)
- hipri flag set

Micro-benchmark results show a net gain of:
- increase of 18%-29% in IOPs
- reduction of 16%-22% in average latency
- reduction of 7%-23% in 99.99% latency

Baseline:
========
QDepth/Batch	| IOPs [k]	| Avg. Lat [us]	| 99.99% Lat [us]
-----------------------------------------------------------------
1/1 		| 32.4		| 30.11		| 50.94
32/8		| 179		| 168.20	| 371

CPU alignment:
=============
QDepth/Batch	| IOPs [k]	| Avg. Lat [us]	| 99.99% Lat [us]
-----------------------------------------------------------------
1/1 		| 38.5		|   25.18	| 39.16
32/8		| 231		|   130.75	| 343

Reported-by: default avatarMark Wunderlich <mark.wunderlich@intel.com>
Signed-off-by: default avatarSagi Grimberg <sagi@grimberg.me>
Signed-off-by: default avatarKeith Busch <kbusch@kernel.org>
parent fa059b85

drivers/nvme/host/tcp.c

+56 −6
Original line number Diff line number Diff line
@@ -1258,13 +1258,67 @@ free_icreq: 
	return ret;

}



static bool nvme_tcp_admin_queue(struct nvme_tcp_queue *queue)

{

	return nvme_tcp_queue_id(queue) == 0;

}



static bool nvme_tcp_default_queue(struct nvme_tcp_queue *queue)

{

	struct nvme_tcp_ctrl *ctrl = queue->ctrl;

	int qid = nvme_tcp_queue_id(queue);



	return !nvme_tcp_admin_queue(queue) &&

		qid < 1 + ctrl->io_queues[HCTX_TYPE_DEFAULT];

}



static bool nvme_tcp_read_queue(struct nvme_tcp_queue *queue)

{

	struct nvme_tcp_ctrl *ctrl = queue->ctrl;

	int qid = nvme_tcp_queue_id(queue);



	return !nvme_tcp_admin_queue(queue) &&

		!nvme_tcp_default_queue(queue) &&

		qid < 1 + ctrl->io_queues[HCTX_TYPE_DEFAULT] +

			  ctrl->io_queues[HCTX_TYPE_READ];

}



static bool nvme_tcp_poll_queue(struct nvme_tcp_queue *queue)

{

	struct nvme_tcp_ctrl *ctrl = queue->ctrl;

	int qid = nvme_tcp_queue_id(queue);



	return !nvme_tcp_admin_queue(queue) &&

		!nvme_tcp_default_queue(queue) &&

		!nvme_tcp_read_queue(queue) &&

		qid < 1 + ctrl->io_queues[HCTX_TYPE_DEFAULT] +

			  ctrl->io_queues[HCTX_TYPE_READ] +

			  ctrl->io_queues[HCTX_TYPE_POLL];

}



static void nvme_tcp_set_queue_io_cpu(struct nvme_tcp_queue *queue)

{

	struct nvme_tcp_ctrl *ctrl = queue->ctrl;

	int qid = nvme_tcp_queue_id(queue);

	int n = 0;



	if (nvme_tcp_default_queue(queue))

		n = qid - 1;

	else if (nvme_tcp_read_queue(queue))

		n = qid - ctrl->io_queues[HCTX_TYPE_DEFAULT] - 1;

	else if (nvme_tcp_poll_queue(queue))

		n = qid - ctrl->io_queues[HCTX_TYPE_DEFAULT] -

				ctrl->io_queues[HCTX_TYPE_READ] - 1;

	queue->io_cpu = cpumask_next_wrap(n - 1, cpu_online_mask, -1, false);

}



static int nvme_tcp_alloc_queue(struct nvme_ctrl *nctrl,

		int qid, size_t queue_size)

{

	struct nvme_tcp_ctrl *ctrl = to_tcp_ctrl(nctrl);

	struct nvme_tcp_queue *queue = &ctrl->queues[qid];

	struct linger sol = { .l_onoff = 1, .l_linger = 0 };

	int ret, opt, rcv_pdu_size, n;

	int ret, opt, rcv_pdu_size;



	queue->ctrl = ctrl;

	INIT_LIST_HEAD(&queue->send_list);
@@ -1343,11 +1397,7 @@ static int nvme_tcp_alloc_queue(struct nvme_ctrl *nctrl, 
	}



	queue->sock->sk->sk_allocation = GFP_ATOMIC;

	if (!qid)

		n = 0;

	else

		n = (qid - 1) % num_online_cpus();

	queue->io_cpu = cpumask_next_wrap(n - 1, cpu_online_mask, -1, false);

	nvme_tcp_set_queue_io_cpu(queue);

	queue->request = NULL;

	queue->data_remaining = 0;

	queue->ddgst_remaining = 0;

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