[PATCH 1/2] SUNRPC: Make rpciod and xprtiod visible in sysfs

[Mike Snitzer <snitzer@kernel.org>]

rpciod and xprtiod are unbound workqueues.  An async task's work is
queued to the affinity pod of the CPU that queues it, but an unbound
workqueue's affinity is not strict by default, so the scheduler is free
to run the worker on any CPU the workqueue allows.  On a two-node NFS
client whose writers are pinned to the node local to their NIC, with
the workqueues' affinity scope set to numa, 1.5% to 2.4% of the skbs
sent on each port were still handed to the driver from the other
node's CPUs: 97% of them from rpciod running rpc_async_schedule(), the
rest from xprtiod.

Neither workqueue can be made strict today, because neither is created
with WQ_SYSFS and so neither has affinity_scope, affinity_strict or
cpumask under /sys/devices/virtual/workqueue/.  Add WQ_SYSFS to both.
Nothing changes until an administrator writes those attributes.

With affinity_strict set to 1 on both, the same client sent nothing
from the other node and spent about 1.7 fewer CPUs at the same
throughput.

Signed-off-by: Mike Snitzer <snitzer@kernel.org>
---
 net/sunrpc/sched.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index 016f16ca57799..83e2974a44d9f 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -1278,11 +1278,11 @@ static int rpciod_start(void)
 	/*
 	 * Create the rpciod thread and wait for it to start.
 	 */
-	wq = alloc_workqueue("rpciod", WQ_MEM_RECLAIM | WQ_UNBOUND, 0);
+	wq = alloc_workqueue("rpciod", WQ_MEM_RECLAIM | WQ_UNBOUND | WQ_SYSFS, 0);
 	if (!wq)
 		goto out_failed;
 	rpciod_workqueue = wq;
-	wq = alloc_workqueue("xprtiod", WQ_UNBOUND | WQ_MEM_RECLAIM, 0);
+	wq = alloc_workqueue("xprtiod", WQ_UNBOUND | WQ_MEM_RECLAIM | WQ_SYSFS, 0);
 	if (!wq)
 		goto free_rpciod;
 	xprtiod_workqueue = wq;
-- 
2.52.0