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https://issues.apache.org/jira/browse/HBASE-15361?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Anoop Sam John resolved HBASE-15361.
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Resolution: Duplicate
> Remove unnecessary or Document constraints on BucketCache possible bucket
> sizes
> --------------------------------------------------------------------------------
>
> Key: HBASE-15361
> URL: https://issues.apache.org/jira/browse/HBASE-15361
> Project: HBase
> Issue Type: Sub-task
> Components: BucketCache
> Reporter: deepankar
> Priority: Minor
>
> When we were trying to tune the bucket sizes
> {{hbase.bucketcache.bucket.sizes}} according to our workload, we encountered
> an issue due to the way offset is stored in the bucket entry. We divide the
> offset into integer base and byte value and it assumes that all bucket
> offsets will be a multiple of 256 (left shifting by 8). See the code below
> {code}
> long offset() { // Java has no unsigned numbers
> long o = ((long) offsetBase) & 0xFFFFFFFF;
> o += (((long) (offset1)) & 0xFF) << 32;
> return o << 8;
> }
> private void setOffset(long value) {
> assert (value & 0xFF) == 0;
> value >>= 8;
> offsetBase = (int) value;
> offset1 = (byte) (value >> 32);
> }
> {code}
> This was there to save 3 bytes per BucketEntry instead of using long and when
> there are no other fields in the Bucket Entry, but now there are lot of
> fields in the bucket entry , This not documented so we could either document
> the constraint that it should be a strict 256 bytes multiple of just go away
> with this constraint.
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