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https://issues.apache.org/jira/browse/CASSANDRA-7882?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14233170#comment-14233170
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Benedict commented on CASSANDRA-7882:
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I've posted a variant of the patch
[here|https://github.com/belliottsmith/cassandra/tree/7882-nativeallocator]
There are a few changes, a couple unrelated just cleaning up the class:
# removed the unslabbed and regionCount variables, as they weren't used for
anything important
# removed the nextRegionSize variable: it wasn't being maintained atomically,
but just as importantly it's messy to do it separately:
#* instead of setting a full region to null, we swap it straight to a new
region, using the prior region to determine the size of the new region
#* we ensure the new region size is at least large enough to hold the
allocation we're inserting
# we cap the size of each "race allocated" queue to 8 entries, as this should
permit plenty of leeway for avoiding heavy competition thrashing the allocator,
but not so much that we have a lot of primarily unused memory
There is one issue, though, which is if this should make it into 2.1, or wait
until 3.0. I'm pretty comfortable either way, but my gut feeling is others will
prefer it wait until 3.0. [~jbellis], what's your view?
> Memtable slab allocation should scale logarithmically to improve occupancy
> rate
> -------------------------------------------------------------------------------
>
> Key: CASSANDRA-7882
> URL: https://issues.apache.org/jira/browse/CASSANDRA-7882
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Jay Patel
> Assignee: Jay Patel
> Labels: performance
> Fix For: 2.1.3
>
> Attachments: trunk-7882.txt
>
>
> CASSANDRA-5935 allows option to disable region-based allocation for on-heap
> memtables but there is no option to disable it for off-heap memtables
> (memtable_allocation_type: offheap_objects).
> Disabling region-based allocation will allow us to pack more tables in the
> schema since minimum of 1MB region won't be allocated per table. Downside can
> be more fragmentation which should be controllable by using better allocator
> like JEMalloc.
> How about below option in yaml?:
> memtable_allocation_type: unslabbed_offheap_objects
> Thanks.
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