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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 Mon, 16 Sep 2013 07:29:54 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9535?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13768128#comment-13768128
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Nicolas Liochon commented on HBASE-9535:
----------------------------------------

bq.  Maybe we should purge the Reader+queuing step and just have Handlers do the read (Nicolas
Liochon what you think?)
I've tried something similar (I removed the handlers and kept the readers), but the performance
was not visible.
The responder seemed to be a bottleneck. But it was not the only issue: we also want to manage
priorities between the tasks, but we need to read them to get enough information to make the
right priorities.

                
> 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
>
> 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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