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Posted to issues@hbase.apache.org by "xuliang0317 (via GitHub)" <gi...@apache.org> on 2026/05/30 15:43:39 UTC
[PR] Xuliang0317 patch 1 [hbase]
xuliang0317 opened a new pull request, #8287:
URL: https://github.com/apache/hbase/pull/8287
Optimize Bloom Filter bit operations by replacing array lookup with bitwise shift
While this is functional, it introduces unnecessary overhead in the read path, which is highly performance-sensitive:
Array Bounds Checking: The JVM must perform bounds checking for every array access to prevent ArrayIndexOutOfBoundsException, which adds minor but cumulative overhead.
Memory Access: Even though bitvals is likely cached in L1/L2 CPU cache, it still requires a memory load instruction.
Division/Modulo Overhead: In BloomFilterChunk#set(long pos), the code uses / 8 and % 8 which compiles to relatively expensive division instructions.
Solution
This PR optimizes the Bloom Filter bit operations by replacing the array lookup with direct bitwise shifts and optimizing the division/modulo operations:
Direct Bitwise Shift: Replaced BloomFilterUtil.bitvals[bitPos] with (1 << bitPos).
This eliminates array bounds checks completely.
The JIT compiler can optimize 1 << bitPos into a single, extremely fast CPU instruction (SHL), executing entirely within CPU registers with zero memory access latency.
Remove Unused Array: Removed the BloomFilterUtil.bitvals array completely to clean up the code.
Division to Shift Optimization: In BloomFilterChunk#set(long pos), replaced pos / 8 and pos % 8 with pos >> 3 and pos & 7. Since pos is always non-negative in this context, this is a safe and much faster alternative to division instructions.
Proposed Changes（去掉了不必要的数字，改成了位运算）
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Re: [PR] Xuliang0317 patch 1 [hbase]
Posted by "xuliang0317 (via GitHub)" <gi...@apache.org>.
xuliang0317 commented on PR #8287:
URL: https://github.com/apache/hbase/pull/8287#issuecomment-4583341896
@Apache9 Could you review this PR when you get a chance?
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Re: [PR] Xuliang0317 patch 1 [hbase]
Posted by "xuliang0317 (via GitHub)" <gi...@apache.org>.
xuliang0317 commented on PR #8287:
URL: https://github.com/apache/hbase/pull/8287#issuecomment-4609748812
@apurtell Could you please take a look at this PR when you have a moment? I'd appreciate any feedback or suggestions you might have. Thanks!
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Re: [PR] HBASE-30205 Optimize Bloom Filter bit operations by replacing array lookup with bitwise shift [hbase]
Posted by "VladRodionov (via GitHub)" <gi...@apache.org>.
VladRodionov commented on PR #8287:
URL: https://github.com/apache/hbase/pull/8287#issuecomment-4721845731
@xuliang0317 Do you observe any measurable performance improvements?
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