Cache ImmutableKeyValuePairs#hashCode #5307
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Codecov ReportPatch coverage:
Additional details and impacted files@@ Coverage Diff @@
## main #5307 +/- ##
=========================================
Coverage 90.97% 90.98%
- Complexity 4907 4908 +1
=========================================
Files 552 552
Lines 14489 14492 +3
Branches 1372 1373 +1
=========================================
+ Hits 13181 13185 +4
Misses 907 907
+ Partials 401 400 -1
... and 1 file with indirect coverage changes Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here. ☔ View full report in Codecov by Sentry. |
jkwatson
reviewed
Mar 17, 2023
| @@ -32,6 +32,7 @@ | |||
| @Immutable | |||
| public abstract class ImmutableKeyValuePairs<K, V> { | |||
| private final Object[] data; | |||
| private int hashcode; | |||
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do we need to mark as volatile for thread safety?
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I dont think so. Reading volatiles isn't free, and its not the end of the world if the hashcode gets computed multiple times.
jkwatson
approved these changes
Mar 18, 2023
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The metrics hot path involves finding the relevant
AggregationHandlein aConcurrentHashmapfor a given measurement based on itsAttributes. We recommend that callers save references to commonAttributesto prevent extra allocations on each measurement. In this case, callers can benefit from cachingAttributes#hashCodeso that it doesn't need to be recomputed each time we record a measurement and do a lookup in theConcurrentHashmap.I've added benchmarks to
AttributesBenchmark, which shows a ~15x improvement in time to computehashCode(not surprising). But its more interesting to see the performance improvement in an actual metrics scenario. I've extendedMetricsBenchmarkto include a case where there's enough cardinality to make the map lookup not completely trivial (the other benchmarks only have a single attributes entry). The performance gains are modest since there's a lot more going on when performing a measurement besides computing a hashcode, but non-zero. Check out the before and after for more details.