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Type: Improvement
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Resolution: Fixed
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Priority: Major - P3
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Affects Version/s: None
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Component/s: None
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Storage Engines
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5
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NachoCheese - 2023-10-03, Joker - StorEng - 2023-10-17, Asparagus-StorEng - 2023-10-31, c(3x10^8)-StorEng - 2023-11-14, 2024-02-20_A_near-death_puffin
Partner ticket to WT-11285 which adds WT_READ_ONCE.
In WiredTiger the WT_PUBLISH macro is currently used for two purposes:
- Providing volatile write semantics which prevents fused writes (taking two write to memory and fusing them into a single write under the hood) and introduced write (taking a single write to memory and converting it into multiple writes under the hood)
- Providing write ordering between two variables. Ensuring that if the code says to write variable A before B that neither the compiler nor CPU execution is allowed to optimise the code to instead write B first.
PM-3221 is splitting these two purposes out into separate macros for clearer readability, and this ticket introduces the WT_WRITE_ONCE macro to handle case 1. Once all uses of WT_PUBLISH to enforce volatile semantics have been updated to use WT_WRITE_ONCE, WT_PUBLISH will be used exclusively to handle case 2.