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https://issues.apache.org/jira/browse/CASSANDRA-6689?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13944217#comment-13944217
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Pavel Yaskevich commented on CASSANDRA-6689:
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bq. My understanding (not my policy) is that this is explicitly not a default
supported option (in the current state of affairs) because of the expectation
of increased heap fragmentation and GC death spiral, which is why I'm happy
with the ugly name for that one option.
So we can go both ways - remove it completely from the allocation type enum and
don't support it or leave it in place and add it to documentation so users can
make informed decision weather to use it or not meanwhile default would still
be "heap_slab" or similar name.
bq. In this case what is to be gained? Seems likely it would only increase the
need for old gen collections, as we wouldn't be able to do any reuse?
It could perform the same function as previous heap slab, for par new it
doesn't make much different but if slab slips to the old get then it would
create less fragmentation comparing to individual buffers getting promoted
(plus we can pack some fresh allocations inside), but that's just an idea and
isn't critical for this ticket...
> Partially Off Heap Memtables
> ----------------------------
>
> Key: CASSANDRA-6689
> URL: https://issues.apache.org/jira/browse/CASSANDRA-6689
> Project: Cassandra
> Issue Type: New Feature
> Components: Core
> Reporter: Benedict
> Assignee: Benedict
> Labels: performance
> Fix For: 2.1 beta2
>
> Attachments: CASSANDRA-6689-final-changes.patch,
> CASSANDRA-6689-small-changes.patch
>
>
> Move the contents of ByteBuffers off-heap for records written to a memtable.
> (See comments for details)
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