colblk: use regular slice in PrefixBytesIter #3872
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We currently store an `unsafe.Pointer` and separate length and capacities. In many cases in the hot path we have to create a slice using `unsafe.Slice`. However `unsafe.Slice` includes some checks that we don't need (see [here](https://github.com/golang/go/blob/f38d42f2c4c6ad0d7cbdad5e1417cac3be2a5dcb/src/runtime/unsafe.go#L53)). In this change we switch to storing a regular slice and converting to an `unsafe.Pointer` using `unsafe.SliceData` (which directly accesses the pointer field). This improves performance, even while gaining boundary checks when appending the suffix. ``` CockroachDataBlockIter/AlphaLen=4,Shared=8,PrefixLen=32,Logical=0,value=8/Next 11.4ns ± 2% 10.6ns ± 1% -7.32% (p=0.008 n=5+5) ```
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jbowens
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nice!
Reviewed 4 of 4 files at r1, all commit messages.
Reviewable status:complete! all files reviewed, all discussions resolved (waiting on @RaduBerinde)
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TFTR! |
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We currently store an
unsafe.Pointerand separate length andcapacities. In many cases in the hot path we have to create a slice
using
unsafe.Slice. Howeverunsafe.Sliceincludes some checks thatwe don't need (see here).
In this change we switch to storing a regular slice and converting to
an
unsafe.Pointerusingunsafe.SliceData(which directly accessesthe pointer field). This improves performance, even while gaining
boundary checks when appending the suffix.