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ConcurrentQueue 128-byte cache line #22724

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Sep 17, 2017
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Original file line number Diff line number Diff line change
Expand Up @@ -1112,10 +1112,10 @@ internal struct Slot

/// <summary>Padded head and tail indices, to avoid false sharing between producers and consumers.</summary>
[DebuggerDisplay("Head = {Head}, Tail = {Tail}")]
[StructLayout(LayoutKind.Explicit, Size = 192)] // padding before/between/after fields based on typical cache line size of 64
[StructLayout(LayoutKind.Explicit, Size = 384)] // padding before/between/after fields based on worst case cache line size of 128
internal struct PaddedHeadAndTail
{
[FieldOffset(64)] public int Head;
[FieldOffset(128)] public int Tail;
[FieldOffset(128)] public int Head;
[FieldOffset(256)] public int Tail;
}
}
Original file line number Diff line number Diff line change
Expand Up @@ -551,7 +551,7 @@ static class PaddingHelpers
}

/// <summary>Padding structure used to minimize false sharing in SingleProducerSingleConsumerQueue{T}.</summary>
[StructLayout(LayoutKind.Explicit, Size = PaddingHelpers.CACHE_LINE_SIZE - sizeof(Int32))] // Based on common case of 64-byte cache lines
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Why did you delete this comment?

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I was out of date and inconsistent with the 128 byte value of CACHE_LINE_SIZE.

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@stephentoub stephentoub Jul 28, 2017

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Ah, I didn't see that the existing value was already set to 128 prior to your change.

[StructLayout(LayoutKind.Explicit, Size = PaddingHelpers.CACHE_LINE_SIZE - sizeof(Int32))]
struct PaddingFor32
{
}
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