Github user JoshRosen commented on the pull request:
https://github.com/apache/spark/pull/9477#issuecomment-153978941
LGTM overall, but I'd like to address one concern before merging: I'm
worried that passing both the `MemoryConsumer` and `TaskMemoryManager` to the
sorter components will open the potential for bugs; I feel that those classes
should allocate their memory using only the public `MemoryConsumer` methods.
Note that the `MemoryConsumer` methods actually end up calling the
`TaskMemoryManager` methods which your code calls directly:
https://github.com/apache/spark/blob/81498dd5c86ca51d2fb351c8ef52cbb28e6844f4/core/src/main/java/org/apache/spark/memory/MemoryConsumer.java#L81
I think that we should mark those TaskMemoryManager methods as methods that
are only supposed to be called _by_ the memory consumer and not directly by
developers. The problem with calling them directly is that the bookkeeping in
the MemoryConsumer itself won't have been updated. This current API has such a
high potential for this type of misuse that I think we should look at fancy
Java-isms to restrict the visibility / callability of those methods such that
they can only be called from MemoryConsumer.
If you fix this by having those classes only allocate through their
MemoryConsumers then feel free to merge as soon as this passes tests. I can
take care of a followup to fix the documentation / code to avoid this type of
misuse.
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