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https://issues.apache.org/jira/browse/HBASE-14757?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14988808#comment-14988808
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Andrew Purtell commented on HBASE-14757:
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For HFileBlock read buffers: These allocations are expected. This is where
block data lands. These allocations are carried through into the block cache
when using the LRUBlockCache and are retained potentially for a very long time.
When using BucketCache, the on-disk block data isn't needed after the IO engine
serializes it off-heap or to SSD. We could reuse allocations for the latter
case but not the former. Needs investigation.
Meanwhile, for block encoding / seeker state, I think these are all short lived
allocations. So, a strawman: Round up byte[] allocation requests here to the
nearest power of 2. Keep object caches for powers of 2 over a common range.
Serve requests from the appropriate free list where available. Prune free lists
using LRU.
> Reduce allocation pressure imposed by HFile block processing
> ------------------------------------------------------------
>
> Key: HBASE-14757
> URL: https://issues.apache.org/jira/browse/HBASE-14757
> Project: HBase
> Issue Type: Improvement
> Reporter: Andrew Purtell
> Assignee: Andrew Purtell
> Fix For: 2.0.0, 1.2.0, 1.3.0, 0.98.17
>
>
> Using Flight Recorder to look at the object allocation profiles of
> regionservers processing the various YCSB workloads when block encoding is
> enabled (specifically, FAST_DIFF, but this applies to any), we can see:
> - Allocations of byte[] for block encoding contribute 40-70% of all
> allocation pressure in TLABs.
> - Of that subset of allocation pressure, ~50-70% is byte[] for SeekerState
> - Greater than 99% of allocation of byte[] outside of TLABs are for read
> buffers for HFileBlock#readBlockDataInternal.
> This issue is for investigation of strategy for and impact of reducing that
> allocation pressure. Reducing allocation pressure reduces demand for GC,
> which reduces GC activity overall, which reduces a source of system latency.
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