[Webkit-unassigned] [Bug 79184] Implement SpinLockMutexLocker on WTF and optimize some parts of JavaScriptCore using it

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=79184





--- Comment #4 from Kwonjin Jeong <gram at company100.net>  2012-02-22 18:18:03 PST ---
(In reply to comment #3)
> How did you confirm that this patch is an optimization?

At first, I compare the performance just between MutexLocker and SpinLockMutexLocker. Upon examination, SpinLockMutexLocker is two times faster than MutexLocker.
I created a performance test program that has a loop within a simple calculation and the Lockers. Then, the program loops one billion times.

And then, I applied SpinLockMutexLocker on some parts of JavaScriptCore, then ran 'run-sunspider', and then compare the results.
Actually, the result using SpinLockMutexLocker is 0.5% ~ 1.0% faster than MutexLocker's - it's within the margin of error.
But I guess that the performance can be better by using SpinLockMutexLocker on some more parts.


My test environment and test result is as written below.
Port: QtWebKit
OS: Linux (Ubuntu 11.10)
CPU: Intel(R) Xeon(R) CPU X5650 @ 2.67GHz (6 core)
RAM: 12GiB

Loop test result:
Mutex        : 17047.357910 ms
SpinLockMutex: 7897.659180 ms
Simple Loop  : 656.346680 ms
Sum          : 565039360

Sunspider result:



The test program is WebKit/Source/JavaScriptCore/jsc.cpp with some modification. I just modify jscmain() function.

int jscmain(int argc, char** argv, JSGlobalData* globalData)
{
    int i;
    int sum = 0;
    Mutex mutex;
    SpinLockMutex spinLockMutex;
    double startTime;
    double endTimeMutexLocker;
    double endTimeSpinLock;
    double endTimeSimpleLoop;
    startTime = currentTime();
    for (i = 0; i < 1000000000; i++) {
        MutexLocker locker(mutex);
        sum += i;
    }
    endTimeMutexLocker = currentTime();
    for (i = 0; i < 1000000000; i++) {
        SpinLockMutexLocker locker(spinLockMutex);
        sum += i;
    }
    endTimeSpinLock = currentTime();
    for (i = 0; i < 1000000000; i++) {
        sum += i;
    }
    endTimeSimpleLoop = currentTime();
    printf("Mutex        : %lf ms\n", endTimeMutexLocker * 1000.0 - startTime * 1000.0);
    printf("SpinLockMutex: %lf ms\n", endTimeSpinLock * 1000.0 - endTimeMutexLocker * 1000.0);
    printf("Simple Loop  : %lf ms\n", endTimeSimpleLoop * 1000.0 - endTimeSpinLock * 1000.0);
    printf("Sum          : %d\n", sum);
    return 0;
}

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