iser-target: Use WQ_UNBOUND for completion workqueue

Bound workqueues might be too restrictive since they allow
only a single core per session for processing completions.
WQ_UNBOUND will allow bouncing to another CPU if the running
CPU is currently busy. Luckily, our workqueues are NUMA aware
and will first try to bounce within the same NUMA socket.
My measurements with NULL backend devices show that there is
no (noticeable) additional latency as a result of the change.
I'd expect even to gain performance when working with fast
devices that also allocate MSIX interrupt vectors.

While we're at it, make it WQ_HIGHPRI since processing
completions is really a high priority for performance.

Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Reported-by: Moussa Ba <moussaba@micron.com>
Signed-off-by: Moussa Ba <moussaba@micron.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

diff --git a/drivers/infiniband/ulp/isert/ib_isert.c b/drivers/infiniband/ulp/isert/ib_isert.c
index 1b35c8a9dceee95f1ffe7d131367489bf986ef75..7f6a0d288f02f7a514ff6d75894c5ec3379d17a6 100644 (file)
--- a/drivers/infiniband/ulp/isert/ib_isert.c
+++ b/drivers/infiniband/ulp/isert/ib_isert.c
@@ -3320,7 +3320,8 @@ static int __init isert_init(void)
 {
        int ret;
 
-       isert_comp_wq = alloc_workqueue("isert_comp_wq", 0, 0);
+       isert_comp_wq = alloc_workqueue("isert_comp_wq",
+                                       WQ_UNBOUND | WQ_HIGHPRI, 0);
        if (!isert_comp_wq) {
                isert_err("Unable to allocate isert_comp_wq\n");
                ret = -ENOMEM;