Change to Hi Res timers on Windows.

There are two parts of this:

1) TimeTicks:Now()
Don't call timeBeginPeriod() in all cases.
Use the new SystemMonitor class to watch battery on/off
transitions and use the timeBeginPeriod() only when we're
using the battery.

2) TimeTicks::UnreliableHiResNow()
Change this function from "UnreliableHiResNow()" to 
"HiResNow()".   We still use QPC, but we detect if we're 
on AMD Athlon XP machines which fail on QPC.  For those
systems, we fall back to TimeTicks::Now().

Updated tests to detect hardware specifics of timers.
Output of the test will contain lines such as these:

[ RUN      ] TimeTicks.SubMillisecondTimers
Min timer is: 1us
[       OK ] TimeTicks.SubMillisecondTimers
[ RUN      ] TimeTicks.TimeGetTimeCaps
timeGetTime range is 1 to 1000000ms
[       OK ] TimeTicks.TimeGetTimeCaps
[ RUN      ] TimeTicks.QueryPerformanceFrequency
QueryPerformanceFrequency is 2394.18MHz
[       OK ] TimeTicks.QueryPerformanceFrequency
[ RUN      ] TimeTicks.TimerPerformance
Time::Now: 0.11us per call
TimeTicks::Now: 0.09us per call
TimeTicks::HighResNow: 0.26us per call
[       OK ] TimeTicks.TimerPerformance



Review URL: http://codereview.chromium.org/4092

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@2625 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 91 insertions, 1 deletions

diff --git a/base/time_unittest_win.cc b/base/time_unittest_win.cc
index 87cf698..4a7120e 100644
--- a/base/time_unittest_win.cc
+++ b/base/time_unittest_win.cc
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include <windows.h>
+#include <mmsystem.h>
 #include <process.h>
 
 #include "base/time.h"
@@ -44,7 +45,9 @@ unsigned __stdcall RolloverTestThreadMain(void* param) {
   for (int index = 0; index < counter; index++) {
     TimeTicks now = TimeTicks::Now();
     int64 milliseconds = (now - last).InMilliseconds();
-    EXPECT_GT(milliseconds, 0);
+    // This is a tight loop; we could have looped faster than our
+    // measurements, so the time might be 0 millis.
+    EXPECT_GE(milliseconds, 0);
     EXPECT_LT(milliseconds, 250);
     last = now;
   }
@@ -99,3 +102,90 @@ TEST(TimeTicks, WinRollover) {
     MockTimeTicks::UninstallTicker();
   }
 }
+
+TEST(TimeTicks, SubMillisecondTimers) {
+  // Loop for a bit getting timers quickly.  We want to
+  // see at least one case where we get a new sample in 
+  // less than one millisecond.
+  bool saw_submillisecond_timer = false;
+  int64 min_timer = 1000;
+  TimeTicks last_time = TimeTicks::HighResNow();
+  for (int index = 0; index < 1000; index++) {
+    TimeTicks now = TimeTicks::HighResNow();
+    TimeDelta delta = now - last_time;
+    if (delta.InMicroseconds() > 0 &&
+        delta.InMicroseconds() < 1000) {
+      if (min_timer > delta.InMicroseconds())
+        min_timer = delta.InMicroseconds();
+      saw_submillisecond_timer = true;
+    }
+    last_time = now;
+  }
+  EXPECT_TRUE(saw_submillisecond_timer);
+  printf("Min timer is: %dus\n", min_timer);
+}
+
+TEST(TimeTicks, TimeGetTimeCaps) {
+  // Test some basic assumptions that we expect about how timeGetDevCaps works.
+
+  TIMECAPS caps;
+  MMRESULT status = timeGetDevCaps(&caps, sizeof(caps));
+  EXPECT_EQ(TIMERR_NOERROR, status);
+  if (status != TIMERR_NOERROR) {
+    printf("Could not get timeGetDevCaps\n");
+    return;
+  }
+
+  EXPECT_GE(static_cast<int>(caps.wPeriodMin), 1);
+  EXPECT_GT(static_cast<int>(caps.wPeriodMax), 1);
+  EXPECT_GE(static_cast<int>(caps.wPeriodMin), 1);
+  EXPECT_GT(static_cast<int>(caps.wPeriodMax), 1);
+  printf("timeGetTime range is %d to %dms\n", caps.wPeriodMin,
+    caps.wPeriodMax);
+}
+
+TEST(TimeTicks, QueryPerformanceFrequency) {
+  // Test some basic assumptions that we expect about QPC.
+
+  LARGE_INTEGER frequency;
+  BOOL rv = QueryPerformanceFrequency(&frequency);
+  EXPECT_EQ(TRUE, rv);
+  EXPECT_GT(frequency.QuadPart, 1000000);  // Expect at least 1MHz
+  printf("QueryPerformanceFrequency is %5.2fMHz\n",
+    frequency.QuadPart / 1000000.0);
+}
+
+TEST(TimeTicks, TimerPerformance) {
+  // Verify that various timer mechanisms can always complete quickly.
+  // Note:  This is a somewhat arbitrary test.
+  const int kLoops = 10000;
+  const int kMaxTime = 10;  // Maximum acceptible milliseconds for test.
+
+  typedef TimeTicks (*TestFunc)();
+  struct TestCase {
+    TestFunc func;
+    char *description;
+  };
+  // Cheating a bit here:  assumes sizeof(TimeTicks) == sizeof(Time)
+  // in order to create a single test case list.
+  COMPILE_ASSERT(sizeof(TimeTicks) == sizeof(Time), 
+                 test_only_works_with_same_sizes);
+  TestCase cases[] = { 
+    { reinterpret_cast<TestFunc>(Time::Now), "Time::Now" },
+    { TimeTicks::Now, "TimeTicks::Now" },
+    { TimeTicks::HighResNow, "TimeTicks::HighResNow" },
+    { NULL, "" }
+  };
+
+  int test_case = 0;
+  while (cases[test_case].func) {
+    TimeTicks start = TimeTicks::HighResNow();
+    for (int index = 0; index < kLoops; index++)
+      cases[test_case].func();
+    TimeTicks stop = TimeTicks::HighResNow();
+    EXPECT_LT((stop - start).InMilliseconds(), kMaxTime);
+    printf("%s: %1.2fus per call\n", cases[test_case].description, 
+      (stop - start).InMillisecondsF() * 1000 / kLoops);
+    test_case++;
+  }
+}