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https://issues.apache.org/jira/browse/CASSANDRA-6689?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13899096#comment-13899096
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Benedict commented on CASSANDRA-6689:
-------------------------------------
There are some natural boundaries if you want to share the burden. Everything
inside of utils.concurrent is pretty isolated from everything outside, so could
easily be vetted independently.
Also, the utilisation of Referrer/RefAction is probably going to be a
painstaking thing to vet (that's what makes the majority of small touches
outside of the main changes), and quite independent of their declarations. We
just need to be certain we always use the correct type of RefAction, and never
let one disappear somewhere - OutboundTCPConnection and native transport
writing are the two danger areas here (also Memtable flushing needs a bit of
care, but is definitely less scary).
The most difficult thing to review is going to be the main body of work inside
of utils.memory, however. This is pretty hardcore lock-free stuff, and the
thing we're looking for is _unintended_ race conditions (there are lots of
intended races) - in particular pay attention to the way in which we now
asynchronously manage the "subpool" and "suballocator" (ledgers of how much
we've allocated / claimed / are reclaiming), and obviously most importantly
that we never accidentally overwrite data that is being read elsewhere. This
should all hopefully be very clearly documented both at the level of
abstraction and the individual points where interesting / dangerous things
happen. But try to figure it out for yourself as well, in case I and my tests
missed something. I will be doing further tests in the near future, but I much
prefer to catch things by eye if possible.
Always feel free to throw up a "this bit isn't well explained" flag and I'll
try to improve it. I want this stuff to be as clearly self documenting as
possible.
> 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
> Fix For: 2.1
>
>
> Move the contents of ByteBuffers off-heap for records written to a memtable.
> (See comments for details)
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