The HIGH cost of ConcurrentBag in .NET 4.0

I got some strange results when using concurrent collections, so I decided to try to track it down, and wrote the following code:

var count = ?;

var list = new List<object>(count);

var sp = Stopwatch.StartNew();

for (int i = 0; i < count; i++)

{

    list.Add(new ConcurrentBag<int>());

}

sp.Stop();

Console.WriteLine("{0} {2} items in {1:#,#;;0}ms = {3:#,#;;0}ms per item",

    sp.Elapsed, sp.ElapsedMilliseconds, count, sp.ElapsedMilliseconds / count);

And then I started to play with the numbers, and it is not good.

10 items in 2ms = 0ms per item

This is incredibly high number, you have to understand. Just to compare, List<int> takes 8 ms to create 100,000 items.

Read more: Ayende @ Rahien

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