Correct LinuxTimer time calculations

Changes to CLOCK_MONOTONIC as CLOCK_PROCESS_CPUTIME counts only user time and not kernel time. BUG=angleproject:892 Change-Id: I3d5aee26ee2bacd7449fdd7795ad8c2b289d7324 Reviewed-on: https://chromium-review.googlesource.com/272652Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Tested-by: Corentin Wallez <cwallez@chromium.org>

Correct LinuxTimer time calculations
5b2545bf · Corentin Wallez · 1b21fd39 · 5b2545bf
Commit 5b2545bf authored May 21, 2015 by Corentin Wallez
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Showing with 7 additions and 4 deletions

LinuxTimer.cpp util/linux/LinuxTimer.cpp +7 -4

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--- a/util/linux/LinuxTimer.cpp
+++ b/util/linux/LinuxTimer.cpp
@@ -7,6 +7,7 @@
 // LinuxTimer.cpp: Implementation of a high precision timer class on Linux

 #include "linux/LinuxTimer.h"
+#include <iostream>

 LinuxTimer::LinuxTimer()
    : mRunning(false)
@@ -15,13 +16,13 @@ LinuxTimer::LinuxTimer()

 void LinuxTimer::start()
 {
-    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &mStartTime);
+    clock_gettime(CLOCK_MONOTONIC, &mStartTime);
    mRunning = true;
 }

 void LinuxTimer::stop()
 {
-    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &mStopTime);
+    clock_gettime(CLOCK_MONOTONIC, &mStopTime);
    mRunning = false;
 }

@@ -30,14 +31,16 @@ double LinuxTimer::getElapsedTime() const
    struct timespec endTime;
    if (mRunning)
    {
-        clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &endTime);
+        clock_gettime(CLOCK_MONOTONIC, &endTime);
    }
    else
    {
        endTime = mStopTime;
    }

-    return endTime.tv_sec + (1.0 / 1000000000) * endTime.tv_nsec;
+    double startSeconds = mStartTime.tv_sec + (1.0 / 1000000000) * mStartTime.tv_nsec;
+    double endSeconds = endTime.tv_sec + (1.0 / 1000000000) * endTime.tv_nsec;
+    return endSeconds - startSeconds;
 }

 Timer *CreateTimer()