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From "Branimir Lambov (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-11541) correct the java documentation for SlabAllocator and NativeAllocator
Date Wed, 04 May 2016 09:31:12 GMT


Branimir Lambov commented on CASSANDRA-11541:

It is not very clear which size is less than 128k in both comments, I would change that phrase
to "allocations of up to 128kb". The 1MB is fixed, "by default" should be removed, perhaps
something like:
large (1MB) global regions and then doles them out to threads that request
smaller sized (up to 128kb) slices into the array.

I believe you mean "exponentially" instead of logarithmically (since for step/scale _n_, size
is 2^_n_) in the second comment, I would change it to:
This NativeAllocator uses global slab allocation strategy with slab size that
scales exponentially from 8kb to 1Mb to serve allocations of up to 128kb.
The slab allocation reduces heap fragmentation from small long-lived objects.

> correct the java documentation for SlabAllocator and NativeAllocator
> --------------------------------------------------------------------
>                 Key: CASSANDRA-11541
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: ZhaoYang
>            Assignee: ZhaoYang
>            Priority: Trivial
>              Labels: document, lhf
>             Fix For: 2.2.x
>         Attachments: CASSANDRA-11541.patch
> I heard a lot that Cassandra uses 2MB slab allocation strategy for memtable to improve
its memory efficiency. But in fact, it has been changed from 2MB to 1 MB. 
> And in NativeAllocator, it's logarithmically from 8kb to 1mb.
> large number of tables may not cause too much trouble in term of memtable.

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