SUNRPC: RPC transport queue must be low latency
rpciod can easily get congested due to the long list of queued rpc_tasks.
Having the receive queue wait in turn for those tasks to complete can
therefore be a bottleneck.
Address the problem by separating the workqueues into:
- rpciod: manages rpc_tasks
- xprtiod: manages transport related work.
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index fcfd48d..a9f7862 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -54,7 +54,8 @@
/*
* rpciod-related stuff
*/
-struct workqueue_struct *rpciod_workqueue;
+struct workqueue_struct *rpciod_workqueue __read_mostly;
+struct workqueue_struct *xprtiod_workqueue __read_mostly;
/*
* Disable the timer for a given RPC task. Should be called with
@@ -1071,10 +1072,22 @@
* Create the rpciod thread and wait for it to start.
*/
dprintk("RPC: creating workqueue rpciod\n");
- /* Note: highpri because network receive is latency sensitive */
- wq = alloc_workqueue("rpciod", WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
+ wq = alloc_workqueue("rpciod", WQ_MEM_RECLAIM, 0);
+ if (!wq)
+ goto out_failed;
rpciod_workqueue = wq;
- return rpciod_workqueue != NULL;
+ /* Note: highpri because network receive is latency sensitive */
+ wq = alloc_workqueue("xprtiod", WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
+ if (!wq)
+ goto free_rpciod;
+ xprtiod_workqueue = wq;
+ return 1;
+free_rpciod:
+ wq = rpciod_workqueue;
+ rpciod_workqueue = NULL;
+ destroy_workqueue(wq);
+out_failed:
+ return 0;
}
static void rpciod_stop(void)
@@ -1088,6 +1101,9 @@
wq = rpciod_workqueue;
rpciod_workqueue = NULL;
destroy_workqueue(wq);
+ wq = xprtiod_workqueue;
+ xprtiod_workqueue = NULL;
+ destroy_workqueue(wq);
}
void