Is Stopwatch.ElapsedTicks threadsafe?

问题

If I have a shared System.Diagnostics.Stopwatch instance, can multiple threads call shared.ElapsedTicks in a safe manner and get accurate results?

Is there any difference in terms of thread-safety/accuracy between using a shared instance of Stopwatch in this way, and using the static GetTimeStamp() method?

I'm measuring intervals of around 180ms, and finding that using the shared instance is giving me a larger spread of results, including a significant number that are shorter than I would expect.

The machine has multiple CPUs (2 * Intel X5550 for what it's worth)

回答1:

From MSDN: "Any instance members are not guaranteed to be thread safe."

回答2:

You can use https://msdn.microsoft.com/en-us/library/dd642243(v=vs.110).aspx

ThreadLocal<T>

like this:

    ThreadLocal<Random> _localRandom = new ThreadLocal<Random>(() => new Random());
    ThreadLocal<Stopwatch> _localStopwatch = new ThreadLocal<Stopwatch>(() => new Stopwatch());

    public void SomeTest()
    {
        Action someAction = () =>
            {
                _localStopwatch.Value.Reset();
                _localStopwatch.Value.Start();
                Thread.Sleep(_localRandom.Value.Next(100, 500));
                _localStopwatch.Value.Stop();
                Debug.Print(_localStopwatch.Value.Elapsed.TotalMilliseconds.ToString(CultureInfo.InvariantCulture));
            };

        var actions = Enumerable.Range(0, 1000).Select(i => someAction).ToArray();
        Parallel.Invoke(new ParallelOptions {MaxDegreeOfParallelism = Environment.ProcessorCount}, actions);
    }

回答3:

Looking at the source code, it is not thread-safe.

回答4:

Looking at the source code, it is thread-safe, but you must not use: Stop(), Reset() and Restart().

So, if you start a shared instance, does not modify it and call only ElapsedXXX properties, you should be fine.

回答5:

To add to the other answers here, while this property is theadsafe as long as you do not call the Start(), Reset(), or Stop() methods, it is important to note that if you are using the ticks for arithmetic and then passing the value into a TimeSpan constructor, for example, one stopWatch.ElapsedTicks Tick is not equivalent to TimeSpan Ticks as described here. To get equivalent ticks you would want to use stopWatch.Elapsed.Ticks.

Would have left this as a comment on another answer but i do not have enough reputation :/

来源：https://stackoverflow.com/questions/6664538/is-stopwatch-elapsedticks-threadsafe

标签

stopwatch