Is DateTime.Now the best way to measure a function's performance?


I need to find a bottleneck and need to accurately as possible measure time.

Is the following code snippet the best way to measure the performance?

DateTime startTime = DateTime.Now;

// Some execution process

DateTime endTime = DateTime.Now;
TimeSpan totalTimeTaken = endTime.Subtract(startTime);
12/21/2011 8:36:54 PM

Accepted Answer

No, it's not. Use the Stopwatch (in System.Diagnostics)

Stopwatch sw = Stopwatch.StartNew();

Console.WriteLine("Time taken: {0}ms", sw.Elapsed.TotalMilliseconds);

Stopwatch automatically checks for the existence of high-precision timers.

It is worth mentioning that DateTime.Now often is quite a bit slower than DateTime.UtcNow due to the work that has to be done with timezones, DST and such.

DateTime.UtcNow typically has a resolution of 15 ms. See John Chapman's blog post about DateTime.Now precision for a great summary.

Interesting trivia: The stopwatch falls back on DateTime.UtcNow if your hardware doesn't support a high frequency counter. You can check to see if Stopwatch uses hardware to achieve high precision by looking at the static field Stopwatch.IsHighResolution.

12/21/2011 8:33:12 PM

If you want something quick and dirty I would suggest using Stopwatch instead for a greater degree of precision.

Stopwatch sw = new Stopwatch();
// Do Work

Console.WriteLine("Elapsed time: {0}", sw.Elapsed.TotalMilliseconds);

Alternatively, if you need something a little more sophisticated you should probably consider using a 3rd party profiler such as ANTS.

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