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From "Nicolas Liochon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9535) Try a pool of direct byte buffers handling incoming ipc requests
Date Tue, 26 Nov 2013 20:36:37 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9535?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13833023#comment-13833023
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Nicolas Liochon commented on HBASE-9535:
----------------------------------------

bq. What do you mean when you say "rpc doesn't work anymore"?
The server gets stuck somewhere. I don't really know where nor why.

bq. On patch, you pull in classes just for your test?
I plan to keep them. The pool is only in hadoop 2, so we need it for hadoop 1 compat. The
ByteBufferInputStream is a technical class. It's public in ZK, but not really part of their
API... And I've done some changes already.

> Try a pool of direct byte buffers handling incoming ipc requests
> ----------------------------------------------------------------
>
>                 Key: HBASE-9535
>                 URL: https://issues.apache.org/jira/browse/HBASE-9535
>             Project: HBase
>          Issue Type: Brainstorming
>            Reporter: stack
>            Assignee: stack
>         Attachments: 9535.v1.patch
>
>
> ipc takes in a query by allocating a ByteBuffer of the size of the request and then reading
off the socket into this on-heap BB.
> Experiment with keeping a pool of BBs so we have some buffer reuse to cut on garbage
generated.  Could checkout from pool in RpcServer#Reader.  Could check back into the pool
when Handler is done just before it queues the response on the Responder's queue.  We should
be good since, at least for now, kvs get copied up into MSLAB (not references) when data gets
stuffed into MemStore; this should make it so no references left over when we check the BB
back into the pool for use next time around.
> If on-heap BBs work, we could then try direct BBs (Allocation of DBBs takes time so if
already allocated, should be good.  GC of DBBs is a pain but if in a pool, we shouldn't be
wanting this to happen).  The copy from socket to the DBB will be off-heap (should be fast).
> Could start w/ the HDFS DirectBufferPool.  It is unbounded and keeps items by size (we
might want to bypass the pool if an object is > size N).
> DBBs for this task would contend w/ offheap BBs used in BlockReadLocal when short-circuit
reading.  It'd be a bummer if we had to allocate big objects on-heap.  Would still be an improvement.



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