default spin count not specified for constructors that don't explicitly set it

[rbwhitaker]

There are three constructors for ManualResetEventSlim. Two don't specify the spin count, while one does. The class is supposed to spin for some amount of time before falling back to a normal wait handle wait. The problem is, I have no clue what the default spin count is, if I don't specify it. By putting in a value, I don't know if I'm speeding it up or slowing it down. The documentation would be better if it could say, "Calling the parameterless constructor makes a new ManualResetEventSlim with a spin count of 10," or if a specific amount isn't something you want to publicly commit to, at least a general idea of what the number is set to, or some hints about the rules that are used to make the decision. Because I don't know what the default is, it's harder to make a decision about which constructor I ought to be using. I suppose my only fallback option is to create it and check the SpinCount property.

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• ID: 094c5713-5b4f-8928-2f63-d6ea692baf27
• Version Independent ID: 0bf6da8d-78a1-9ada-46f7-7e8bc8ae8146
• Content: ManualResetEventSlim Constructor (System.Threading)
• Content Source: xml/System.Threading/ManualResetEventSlim.xml
• Product: .net
• GitHub Login: @dotnet-bot
• Microsoft Alias: dotnetcontent

[mairaw]

Specifying the default values is generally a good practice @rbwhitaker. We can add that info to the docs.

The default value will vary depending if the machine is single processor or multi processor:
https://referencesource.microsoft.com/#mscorlib/system/threading/ManualResetEventSlim.cs,56

It also seems that different .NET implementations have different defaults:
https://github.com/dotnet/corefx/blob/master/src/Common/src/CoreLib/System/Threading/SpinWait.cs#L90

/cc @Kouver

[mairaw]

Moving to the backlog for now.