disk bucket allocated bit can be not in header #30834
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jeffwashington
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brooksprumo
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bucket_map/src/bucket_storage.rs
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| InHeader, | ||
| } | ||
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| const FLAG_LOCATION: IsAllocatedFlagLocation = IsAllocatedFlagLocation::InHeader; |
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When I see FLAG_LOCATION by itself in the code, I first think "which flag?". Right now I have the context in my head, so the lookup is fast. And this constant is in the same file, so it'll fast later too. My preferences tend to be more verbose, maybe something along these lines is pleasing to you too?
Suggested change
| const FLAG_LOCATION: IsAllocatedFlagLocation = IsAllocatedFlagLocation::InHeader; | |
| const IS_ALLOCATED_FLAG_LOCATION: IsAllocatedFlagLocation = IsAllocatedFlagLocation::InHeader; |
Codecov Report
@@ Coverage Diff @@
## master #30834 +/- ##
=======================================
Coverage 81.4% 81.4%
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Files 723 723
Lines 203533 203538 +5
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+ Hits 165845 165872 +27
+ Misses 37688 37666 -22 |
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Problem
See #30711
If we store the single bit for 'allocated' status somewhere other than the header of each element, we save 8 bytes per element. Also remember the disk index is possibly 2x over-allocated.
Storage options include:
ref_count's high bitsSummary of Changes
Placeholders for removing the allocated bit from the header.
Fixes #