[jira] [Updated] (HBASE-11351) Experiments with OffHeap memstores

["Lars Hofhansl (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-11351?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Lars Hofhansl updated HBASE-11351:
----------------------------------

    Attachment: 11351-0.94.txt

Here's the hacked up patch.
WARNING: Total hack.
* For some reason MapDB wants *everything* Serializable
* All code in Memstore.java
* Currently KVs are serialized twice into the off heap map (could work around this if we forked MapDB NavigableSet implementation).
* Much slower
* Generates more GC churn (but should be young gen only)
* 0.94 only right now
* Just for playing!


> Experiments with OffHeap memstores
> ----------------------------------
>
>                 Key: HBASE-11351
>                 URL: https://issues.apache.org/jira/browse/HBASE-11351
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>         Attachments: 11351-0.94.txt
>
>
> I have been experimenting with offheap memstores using an offheap BTree implementation of ConcurrentMap provided by MapDB (www.mapdb.org)
> So far I hooked this up in an experimental way with inefficient serialization (in the sense that due to our special usage of the set api we need to back the set by a map, which in the off heap case means we need to serialize and store the value twice. It is used as key and value). But it works.
> It's quite a bit slower and due to need to deserialize upon scan it produces *more* short term garbage.
> Let's use this issue to discuss.



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