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From "Tim Armstrong (Code Review)" <ger...@cloudera.org>
Subject [Impala-ASF-CR] IMPALA-3200: Implement suballocator for splitting buffers
Date Mon, 21 Nov 2016 19:25:35 GMT
Tim Armstrong has posted comments on this change.

Change subject: IMPALA-3200: Implement suballocator for splitting buffers
......................................................................


Patch Set 5:

(1 comment)

http://gerrit.cloudera.org:8080/#/c/4715/5/be/src/bufferpool/suballocator.h
File be/src/bufferpool/suballocator.h:

PS5, Line 66: Suballocations are eagerly coalesced when freed
> Is the coalescing only one level or does it recurse all the way up the tree
It coalesces all the way up. It's much simpler to eagerly coalesce since it greatly reduces
the number of possible states the allocator can be in. I think that in turn makes it easier
to reason about fragmentation (although eagerly coalescing should minimise fragmentation since
it also guarantees that the smallest contiguous memory range available is used for an allocation).

I'm not sure about FreePool. Mainly for now I want to make sure we have an allocator that
works well for larger allocations - particularly the hash table use case. For the immediate
future it could continue to operate on top of MemPool, even once MemPool is converted to use
BufferPool buffers.


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Gerrit-MessageType: comment
Gerrit-Change-Id: I8bfe0e429f67ad273f7c7d0816703a9e6c3da788
Gerrit-PatchSet: 5
Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-Owner: Tim Armstrong <tarmstrong@cloudera.com>
Gerrit-Reviewer: Jim Apple <jbapple@cloudera.com>
Gerrit-Reviewer: Michael Ho
Gerrit-Reviewer: Michael Ho <kwho@cloudera.com>
Gerrit-Reviewer: Tim Armstrong <tarmstrong@cloudera.com>
Gerrit-HasComments: Yes

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