Fix bug in HyperClockCache ApplyToEntries; cleanup #10768
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Summary: We have seen some rare crash test failures in HyperClockCache, and the source could certainly be a bug fixed in this change, in ClockHandleTable::ConstApplyToEntriesRange. It wasn't properly accounting for the fact that incrementing the acquire counter could be ineffective, due to parallel updates. (When incrementing the acquire counter is ineffective, it is incorrect to then decrement it.) This change includes some other minor clean-up in HyperClockCache, and adds stats_dump_period_sec with a much lower period to the crash test. This should be the primary caller of ApplyToEntries, in collecting cache entry stats. Test Plan: haven't been able to reproduce the failure, but should be in a better state
…ache_apply_entries_bug
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anand1976
approved these changes
Oct 6, 2022
tools/db_crashtest.py
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| @@ -137,6 +137,7 @@ | |||
| "index_block_restart_interval": lambda: random.choice(range(1, 16)), | |||
| "use_multiget": lambda: random.randint(0, 1), | |||
| "periodic_compaction_seconds": lambda: random.choice([0, 0, 1, 2, 10, 100, 1000]), | |||
| "stats_dump_period_sec": lambda: random.choice([0, 30]), | |||
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Is there any reason to set it to 0 (disable)? Maybe use the default of 600 instead of 0.
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I know we have at least one internal user setting to 0. Hypothetically, if stats dump does some kind of reset on some data that prevents some overflow when run periodically, it could hide a bug. That's hypothetical but I think sufficiently motivates 0. Perhaps I'll do [0, 10, 600].
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Summary: We have seen some rare crash test failures in HyperClockCache, and the source could certainly be a bug fixed in this change, in ClockHandleTable::ConstApplyToEntriesRange. It wasn't properly accounting for the fact that incrementing the acquire counter could be ineffective, due to parallel updates. (When incrementing the acquire counter is ineffective, it is incorrect to then decrement it.) This change includes some other minor clean-up in HyperClockCache, and adds stats_dump_period_sec with a much lower period to the crash test. This should be the primary caller of ApplyToEntries, in collecting cache entry stats. Pull Request resolved: #10768 Test Plan: haven't been able to reproduce the failure, but should be in a better state (bug fix and improved crash test) Reviewed By: anand1976 Differential Revision: D40034747 Pulled By: anand1976 fbshipit-source-id: a06fcefe146e17ee35001984445cedcf3b63eb68
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Summary: We have seen some rare crash test failures in HyperClockCache, and the source could certainly be a bug fixed in this change, in ClockHandleTable::ConstApplyToEntriesRange. It wasn't properly accounting for the fact that incrementing the acquire counter could be ineffective, due to parallel updates. (When incrementing the acquire counter is ineffective, it is incorrect to then decrement it.)
This change includes some other minor clean-up in HyperClockCache, and adds stats_dump_period_sec with a much lower period to the crash test. This should be the primary caller of ApplyToEntries, in collecting cache entry stats.
Test Plan: haven't been able to reproduce the failure, but should be in a better state (bug fix and improved crash test)