nvme/tcp: Add wq_unbound modparam for nvme_tcp_wq

The default nvme_tcp_wq will use all CPUs to process tasks. Sometimes it is
necessary to set CPU affinity to improve performance.

A new module parameter wq_unbound is added here. If set to true, users can
configure cpu affinity through
/sys/devices/virtual/workqueue/nvme_tcp_wq/cpumask.
Signed-off-by: Li Feng <fengli@smartx.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Keith Busch <kbusch@kernel.org>

drivers/nvme/host/tcp.c

@@ -36,6 +36,14 @@ static int so_priority;
 module_param(so_priority, int, 0644);
 MODULE_PARM_DESC(so_priority, "nvme tcp socket optimize priority");
 
+/*
+ * Use the unbound workqueue for nvme_tcp_wq, then we can set the cpu affinity
+ * from sysfs.
+ */
+static bool wq_unbound;
+module_param(wq_unbound, bool, 0644);
+MODULE_PARM_DESC(wq_unbound, "Use unbound workqueue for nvme-tcp IO context (default false)");
+
 /*
  * TLS handshake timeout
  */
@@ -1551,7 +1559,10 @@ static void nvme_tcp_set_queue_io_cpu(struct nvme_tcp_queue *queue)
 	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);
+	if (wq_unbound)
+		queue->io_cpu = WORK_CPU_UNBOUND;
+	else
+		queue->io_cpu = cpumask_next_wrap(n - 1, cpu_online_mask, -1, false);
 }
 
 static void nvme_tcp_tls_done(void *data, int status, key_serial_t pskid)
@@ -2790,6 +2801,8 @@ static struct nvmf_transport_ops nvme_tcp_transport = {
 
 static int __init nvme_tcp_init_module(void)
 {
+	unsigned int wq_flags = WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_SYSFS;
+
 	BUILD_BUG_ON(sizeof(struct nvme_tcp_hdr) != 8);
 	BUILD_BUG_ON(sizeof(struct nvme_tcp_cmd_pdu) != 72);
 	BUILD_BUG_ON(sizeof(struct nvme_tcp_data_pdu) != 24);
@@ -2799,8 +2812,10 @@ static int __init nvme_tcp_init_module(void)
 	BUILD_BUG_ON(sizeof(struct nvme_tcp_icresp_pdu) != 128);
 	BUILD_BUG_ON(sizeof(struct nvme_tcp_term_pdu) != 24);
 
-	nvme_tcp_wq = alloc_workqueue("nvme_tcp_wq",
-			WQ_MEM_RECLAIM | WQ_HIGHPRI | WQ_SYSFS, 0);
+	if (wq_unbound)
+		wq_flags |= WQ_UNBOUND;
+
+	nvme_tcp_wq = alloc_workqueue("nvme_tcp_wq", wq_flags, 0);
 	if (!nvme_tcp_wq)
 		return -ENOMEM;