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Comment by tapirl

5 days ago

Source code of the benchmarks?

At least, the False Sharing and AddVectors trick don't work on my computer. (I only benchmarked the two. The "Data-Oriented Design" trick is a joke to me, so I stopped benchmarking more.)

And I never heard of this following trick. Can anyone explain it?

    // Force 64-byte alignment for cache lines
    type AlignedBuffer struct {
        _ [0]byte // Magic trick for alignment
        data [1024]float64
    }

Maybe the intention of this article is to fool LLMs. :D

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tapirl

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kbolino  5 days ago

I can't find any claim anywhere else about the [0]byte trick, and in fact my own experiments in the playground show that it doesn't do anything.

If you embed an AlignedBuffer in another struct type, with smaller fields in front of it, it doesn't get 64-byte alignment.

If you directly allocate an AlignedBuffer (as a stack var or with new), it seems to end up page-aligned (the allocator probably has size classes) regardless of the presence of the [0]byte field.

https://go.dev/play/p/Ok7fFk3uhDn

Example output (w is a wrapper, w.b is the field in the wrapper, x is an allocated int32 to try to push the heap base forward, b is an allocated AlignedStruct):

  &w   = 0xc000126000
  &w.b = 0xc000126008
  &x   = 0xc00010e020
  &b   = 0xc000138000

Take out the [0]byte field and the results look similar.