SUNRPC: Micro-optimize __rpc_execute

The common case: There are 13 to 14 actions per RPC, and tk_callback
is non-NULL in only one of them. There's no need to store a NULL in
the tk_callback field during each FSM step.

This slightly improves throughput results in dbench and other multi-
threaded benchmarks on my two-socket client on 56Gb InfiniBand, but
will probably be inconsequential on slower systems.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

1 files changed, 11 insertions, 13 deletions

diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index c292a5e1a70c..896691afbb1a 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -755,21 +755,19 @@ static void __rpc_execute(struct rpc_task *task)
                 void (*do_action)(struct rpc_task *);
 
                 /*
-                 * Execute any pending callback first.
+                 * Perform the next FSM step or a pending callback.
+                 *
+                 * tk_action may be NULL if the task has been killed.
+                 * In particular, note that rpc_killall_tasks may
+                 * do this at any time, so beware when dereferencing.
                  */
-                do_action = task->tk_callback;
-                task->tk_callback = NULL;
-                if (do_action == NULL) {
-                        /*
-                         * Perform the next FSM step.
-                         * tk_action may be NULL if the task has been killed.
-                         * In particular, note that rpc_killall_tasks may
-                         * do this at any time, so beware when dereferencing.
-                         */
-                        do_action = task->tk_action;
-                        if (do_action == NULL)
-                                break;
+                do_action = task->tk_action;
+                if (task->tk_callback) {
+                        do_action = task->tk_callback;
+                        task->tk_callback = NULL;
                 }
+                if (!do_action)
+                        break;
                 trace_rpc_task_run_action(task->tk_client, task, do_action);
                 do_action(task);