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From Ted Dunning <tdunn...@maprtech.com>
Subject Re: Hadoop RPC call response post processing
Date Tue, 28 Dec 2010 07:21:31 GMT
I would be very surprised if allocation itself is the problem as opposed to
good old fashioned excess copying.

It is very hard to write an allocator faster than the java generational gc,
especially if you are talking about objects that are ephemeral.

Have you looked at the tenuring distribution?

On Mon, Dec 27, 2010 at 8:07 PM, Stefan Groschupf <sg@101tec.com> wrote:

> Hi All,
> I'm browsing the RPC code since quite a while now trying to find any entry
> point / interceptor slot that allows me to handle a RPC call response
> writable after it was send over the wire.
> Does anybody has an idea how break into the RPC code from outside. All the
> interesting methods are private. :(
>
> Background:
> Heavy use of the RPC allocates hugh amount of Writable objects. We saw in
> multiple systems  that the garbage collect can get so busy that the jvm
> almost freezes for seconds. Things like zookeeper sessions time out in that
> cases.
> My idea is to create an object pool for writables. Borrowing an object from
> the pool is simple since this happen in our custom code, though we do know
> when the writable return was send over the wire and can be returned into the
> pool.
> A dirty hack would be to overwrite the write(out) method in the writable,
> assuming that is the last thing done with the writable, though turns out
> that this method is called in other cases too, e.g. to measure throughput.
>
> Any ideas?
>
> Thanks,
> Stefan

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