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https://issues.apache.org/jira/browse/HBASE-14918?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15163424#comment-15163424
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stack commented on HBASE-14918:
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bq. ....the CellBlocks suggests to use ArrayList of PositionedByteRange as the
underlying data structure.
You thinking this still the case [~anoop.hbase] given where offheaping of read
path is going? Should base type be ByteBuff so can do onheap/offheap?
bq, Thus we suggest CellBlocksSegment, which fits into new Segments structure
of MemStore and inherits from ImmutableSegment.
High-level, sounds good.
bq. Underneath, CellBlocksSegment has the same idea of CellBlock.
One question; what happens when a CellBlockSegment runs into a HFileBlock? How
will the marshalling from CBS to HFB run?
bq. Just striving to use an array of arrays, instead of list of arrays, in
order to enjoy the binary search and less memory overhead.
A noble goal.
So, an array of CellBlocks? You'd allocate CellBlocks with MSLAB?
bq. As far as for now MSLAB doesn't support off-heap allocation, the
PositionedByteRange can be replaced by ByteRange/Chunk currently returned by
MSLAB. Also little more tuning is required.
Ok. Sorry for the plethora of types. We seem to be settling on a few now we
know more.
There also means of allocation. MSLAB, BucketCache allocator.
We can move BBBP no problem.
Yeah, lets align what you are doing here with the offheaping of the write path
work @anastasia.
bq. Sorry for this long monolog
Keep going. It is good stuff.
> In-Memory MemStore Flush and Compaction
> ---------------------------------------
>
> Key: HBASE-14918
> URL: https://issues.apache.org/jira/browse/HBASE-14918
> Project: HBase
> Issue Type: Umbrella
> Affects Versions: 2.0.0
> Reporter: Eshcar Hillel
> Assignee: Eshcar Hillel
> Fix For: 0.98.18
>
> Attachments: CellBlocksSegmentDesign.pdf, MSLABMove.patch
>
>
> A memstore serves as the in-memory component of a store unit, absorbing all
> updates to the store. From time to time these updates are flushed to a file
> on disk, where they are compacted (by eliminating redundancies) and
> compressed (i.e., written in a compressed format to reduce their storage
> size).
> We aim to speed up data access, and therefore suggest to apply in-memory
> memstore flush. That is to flush the active in-memory segment into an
> intermediate buffer where it can be accessed by the application. Data in the
> buffer is subject to compaction and can be stored in any format that allows
> it to take up smaller space in RAM. The less space the buffer consumes the
> longer it can reside in memory before data is flushed to disk, resulting in
> better performance.
> Specifically, the optimization is beneficial for workloads with
> medium-to-high key churn which incur many redundant cells, like persistent
> messaging.
> We suggest to structure the solution as 4 subtasks (respectively, patches).
> (1) Infrastructure - refactoring of the MemStore hierarchy, introducing
> segment (StoreSegment) as first-class citizen, and decoupling memstore
> scanner from the memstore implementation;
> (2) Adding StoreServices facility at the region level to allow memstores
> update region counters and access region level synchronization mechanism;
> (3) Implementation of a new memstore (CompactingMemstore) with non-optimized
> immutable segment representation, and
> (4) Memory optimization including compressed format representation and off
> heap allocations.
> This Jira continues the discussion in HBASE-13408.
> Design documents, evaluation results and previous patches can be found in
> HBASE-13408.
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