Avoid excessive reallocation in row compressors #6638
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Codecov ReportAll modified and coverable lines are covered by tests ✅
Additional details and impacted files@@ Coverage Diff @@
## main #6638 +/- ##
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- Coverage 80.04% 80.01% -0.03%
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Files 190 190
Lines 37179 37135 -44
Branches 9450 9433 -17
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- Hits 29761 29715 -46
- Misses 3003 3016 +13
+ Partials 4415 4404 -11 ☔ View full report in Codecov by Sentry. |
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@svenklemm, @erimatnor: please review this pull request.
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fabriziomello
approved these changes
Feb 13, 2024
nikkhils
reviewed
Feb 14, 2024
| simple8brle_compressor_init(&compressor->bits_used_per_xor); | ||
| bit_array_init(&compressor->xors); | ||
| bit_array_init(&compressor->xors, | ||
| /* expected_bits = */ GLOBAL_MAX_ROWS_PER_COMPRESSION * 12); |
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Typical value we observe for some data sets. I'll add a comment.
Memory operations can add up to tens of percents of the total compression CPU load. To reduce the need for them, reserve for the expected array sizes when initializing the compressor.
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Memory operations can add up to tens of percents of the total
compression CPU load. To reduce the need for them, reserve for the
expected array sizes when initializing the compressor.
Based on measurements in this issue: https://github.com/timescale/Support-Dev-Collab/issues/1498#issuecomment-1936607692
We don't have a dataset which reproduces it well in tsbench, but I think it's a safe change anyway: https://grafana.ops.savannah-dev.timescale.com/d/fasYic_4z/compare-akuzm?orgId=1&var-branch=All&var-run1=3238&var-run2=3239&var-threshold=0.02&var-use_historical_thresholds=true&var-threshold_expression=2.5%20%2A%20percentile_cont%280.90%29&var-exact_suite_version=true
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