interval/generic: avoid letting argument to FirstOverlap escape to heap#45423
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craig[bot] merged 2 commits intocockroachdb:masterfrom Feb 26, 2020
Merged
interval/generic: avoid letting argument to FirstOverlap escape to heap#45423craig[bot] merged 2 commits intocockroachdb:masterfrom
craig[bot] merged 2 commits intocockroachdb:masterfrom
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This was hiding the fact that FirstOverlap caused its argument to escape to the heap, forcing an allocation for some callers. The benchmarks now capture this: ``` name time/op BTreeIterFirstOverlap/count=16-16 400ns ± 1% BTreeIterFirstOverlap/count=128-16 661ns ± 0% BTreeIterFirstOverlap/count=1024-16 1.15µs ± 2% BTreeIterFirstOverlap/count=8192-16 1.84µs ± 2% BTreeIterFirstOverlap/count=65536-16 2.62µs ± 2% BTreeIterNextOverlap-16 11.1ns ± 2% BTreeIterOverlapScan-16 34.2µs ± 1% name alloc/op BTreeIterFirstOverlap/count=16-16 96.0B ± 0% BTreeIterFirstOverlap/count=128-16 96.0B ± 0% BTreeIterFirstOverlap/count=1024-16 96.0B ± 0% BTreeIterFirstOverlap/count=8192-16 96.0B ± 0% BTreeIterFirstOverlap/count=65536-16 96.0B ± 0% BTreeIterNextOverlap-16 0.00B BTreeIterOverlapScan-16 144B ± 0% name allocs/op BTreeIterFirstOverlap/count=16-16 1.00 ± 0% BTreeIterFirstOverlap/count=128-16 1.00 ± 0% BTreeIterFirstOverlap/count=1024-16 1.00 ± 0% BTreeIterFirstOverlap/count=8192-16 1.00 ± 0% BTreeIterFirstOverlap/count=65536-16 1.00 ± 0% BTreeIterNextOverlap-16 0.00 BTreeIterOverlapScan-16 6.40 ± 9% ```
Related to cockroachdb#45276. Prior to this change, the argument provided to `iterator.FirstOverlap` was stored in the iterator. This caused the argument to escape to the heap (if the parameterized type was a pointer) and would force an allocation if the argument was not already on the heap. This was not the intention and was causing issues in cockroachdb#45276. This commit fixes the issue by no longer storing the argument in the iterator's `overlapScan` object. This allows escape analysis to determine that the argument does not escape, like it was already doing for `iterator.SeekGE` and `iterator.SeekLT`. ``` name old time/op new time/op delta BTreeIterFirstOverlap/count=16-16 400ns ± 1% 325ns ± 5% -18.75% (p=0.008 n=5+5) BTreeIterFirstOverlap/count=128-16 661ns ± 0% 581ns ± 1% -12.02% (p=0.008 n=5+5) BTreeIterFirstOverlap/count=1024-16 1.15µs ± 2% 1.07µs ± 2% -6.76% (p=0.008 n=5+5) BTreeIterFirstOverlap/count=8192-16 1.84µs ± 2% 1.76µs ± 2% -4.38% (p=0.016 n=5+5) BTreeIterFirstOverlap/count=65536-16 2.62µs ± 2% 2.52µs ± 1% -4.07% (p=0.008 n=5+5) BTreeIterNextOverlap-16 11.1ns ± 2% 10.7ns ± 0% -3.95% (p=0.016 n=5+4) BTreeIterOverlapScan-16 34.2µs ± 1% 31.2µs ± 1% -8.78% (p=0.008 n=5+5) name old alloc/op new alloc/op delta BTreeIterFirstOverlap/count=16-16 96.0B ± 0% 0.0B -100.00% (p=0.008 n=5+5) BTreeIterFirstOverlap/count=128-16 96.0B ± 0% 0.0B -100.00% (p=0.008 n=5+5) BTreeIterFirstOverlap/count=1024-16 96.0B ± 0% 0.0B -100.00% (p=0.008 n=5+5) BTreeIterFirstOverlap/count=8192-16 96.0B ± 0% 0.0B -100.00% (p=0.008 n=5+5) BTreeIterFirstOverlap/count=65536-16 96.0B ± 0% 0.0B -100.00% (p=0.008 n=5+5) BTreeIterNextOverlap-16 0.00B 0.00B ~ (all equal) BTreeIterOverlapScan-16 144B ± 0% 48B ± 0% -66.67% (p=0.008 n=5+5) name old allocs/op new allocs/op delta BTreeIterFirstOverlap/count=16-16 1.00 ± 0% 0.00 -100.00% (p=0.008 n=5+5) BTreeIterFirstOverlap/count=128-16 1.00 ± 0% 0.00 -100.00% (p=0.008 n=5+5) BTreeIterFirstOverlap/count=1024-16 1.00 ± 0% 0.00 -100.00% (p=0.008 n=5+5) BTreeIterFirstOverlap/count=8192-16 1.00 ± 0% 0.00 -100.00% (p=0.008 n=5+5) BTreeIterFirstOverlap/count=65536-16 1.00 ± 0% 0.00 -100.00% (p=0.008 n=5+5) BTreeIterNextOverlap-16 0.00 0.00 ~ (all equal) BTreeIterOverlapScan-16 6.40 ± 9% 5.00 ± 0% -21.88% (p=0.008 n=5+5) ```
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Reviewed 7 of 7 files at r2.
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Related to #45276.
Prior to this change, the argument provided to
iterator.FirstOverlapwas stored in the iterator. This caused the argument to escape to the heap (if the parameterized type was a pointer) and would force an allocation if the argument was not already on the heap. This was not the intention and was causing issues in #45276.This commit fixes the issue by no longer storing the argument in the iterator's
overlapScanobject. This allows escape analysis to determine that the argument does not escape, like it was already doing foriterator.SeekGEanditerator.SeekLT.