schedbench tweaks

02d8b289 · Silas Boyd-Wickizer · e855e8e8 · 02d8b289
--- a/bin/schedbench.cc
+++ b/bin/schedbench.cc
@@ -7,6 +7,7 @@
 #include "atomic.hh"

 static volatile std::atomic<u64> waiting;
+static volatile std::atomic<u64> waking;
 static volatile u64 ftx;
 static int iters;
 static int nworkers;
@@ -15,13 +16,17 @@ static
 void* worker(void* x)
 {
  long r;
+  int i;

-  for (int i = 0; i < iters; i++) {
+  for (i = 0; i < iters; i++) {
    ++waiting;
    r = futex((u64*)&ftx, FUTEX_WAIT, (u64)i, 0);
    if (r < 0 && r != -EWOULDBLOCK)
      die("FUTEX_WAIT: %d", r);
+    while (waking.load() == 1)
+      nop_pause();
  }
+
  return nullptr;
 }

@@ -31,13 +36,14 @@ void master(void)
  long r;

  for (int i = 0; i < iters; i++) {
-    while (waiting.load() < nworkers)
+    while (waiting.load() < (i+1)*nworkers)
      nop_pause();
-    waiting.store(0);
-
+    
+    waking.store(1);
    ftx = i+1;
    r = futex((u64*)&ftx, FUTEX_WAKE, nworkers, 0);  
    assert(r == 0);
+    waking.store(0);
  }
 }

@@ -48,6 +54,7 @@ main(int ac, char** av)

  if (ac < 3)
    die("usage: %s iters nworkers", av[0]);
+  ftx = 0;
  iters = atoi(av[1]);
  nworkers = atoi(av[2]);
  waiting.store(0);