Add -l N option to limit the load average.

This is similar to GNU make -l/--load-average option.  It limits the number
of job started if the load average exceed the given value.  It can be very
useful when running ninja on a continuous integration server where we want
to use parallelism as much as possible without overloading the server.

1 files changed, 29 insertions, 0 deletions

diff --git a/src/util.cc b/src/util.cc
index c88dc4e..73f13f8 100644
--- a/src/util.cc
+++ b/src/util.cc
@@ -293,3 +293,32 @@ string StripAnsiEscapeCodes(const string& in) {
   }
   return stripped;
 }
+
+#ifdef _WIN32
+static double GetLoadAverage_win32()
+{
+  // TODO(nicolas.despres@gmail.com): Find a way to implement it on Windows.
+  return -0.0f;
+}
+#else
+static double GetLoadAverage_unix()
+{
+  double loadavg[3] = { 0.0f, 0.0f, 0.0f };
+  if (getloadavg(loadavg, 3) < 0)
+  {
+    // Maybe we should return an error here or the availability of
+    // getloadavg(3) should be checked when ninja is configured.
+    return -0.0f;
+  }
+  return loadavg[0];
+}
+#endif // _WIN32
+
+double GetLoadAverage()
+{
+#ifdef _WIN32
+  return GetLoadAverage_win32();
+#else
+  return GetLoadAverage_unix();
+#endif // _WIN32
+}