winio: Queue IO processing threads at the front of the queue.

This will unblock the IO thread sooner hopefully leading to higher
throughput in some situations.

3 files changed, 13 insertions, 1 deletions

diff --git a/rts/Schedule.c b/rts/Schedule.c
index 8c120c093e..6b10326859 100644
--- a/rts/Schedule.c
+++ b/rts/Schedule.c
@@ -2577,6 +2577,14 @@ scheduleThread(Capability *cap, StgTSO *tso)
 }
 
 void
+scheduleThreadNow(Capability *cap, StgTSO *tso)
+{
+    // The thread goes at the *beginning* of the run-queue,
+    // in order to execute it as soon as possible.
+    pushOnRunQueue(cap,tso);
+}
+
+void
 scheduleThreadOn(Capability *cap, StgWord cpu USED_IF_THREADS, StgTSO *tso)
 {
     tso->flags |= TSO_LOCKED; // we requested explicit affinity; don't
diff --git a/rts/Schedule.h b/rts/Schedule.h
index 89ab6e0b4c..a550a6763a 100644
--- a/rts/Schedule.h
+++ b/rts/Schedule.h
@@ -27,6 +27,10 @@ void markScheduler (evac_fn evac, void *user);
 // Place a new thread on the run queue of the current Capability
 void scheduleThread (Capability *cap, StgTSO *tso);
 
+// Place a new thread on the run queue of the current Capability
+// at the front of the queue.
+void scheduleThreadNow (Capability *cap, StgTSO *tso);
+
 // Place a new thread on the run queue of a specified Capability
 // (cap is the currently owned Capability, cpu is the number of
 // the desired Capability).
diff --git a/rts/win32/AsyncWinIO.c b/rts/win32/AsyncWinIO.c
index 6bacf48eb1..a280c28bde 100644
--- a/rts/win32/AsyncWinIO.c
+++ b/rts/win32/AsyncWinIO.c
@@ -426,7 +426,7 @@ bool queueIOThread()
       StgTSO * tso = createStrictIOThread (cap, RtsFlags.GcFlags.initialStkSize,
                                           processRemoteCompletion_closure);
       ASSERT(tso);
-      scheduleThread (cap, tso);
+      scheduleThreadNow (cap, tso);
       result = true;
   }
   ReleaseSRWLockExclusive (&lock);