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From gregory james marsh <mars...@cse.ohio-state.edu>
Subject Re: AMQP Paper, using Qpid
Date Wed, 12 Nov 2008 17:48:26 GMT



Hi Carl,

A question from our group about the following client params you mentioned
in your email (included below):

  --max-frame-size N (65535)        the maximum frame size to request.
  --bounds-multiplier N (2)         bound size of write queue (as a
multiple of
                                    the max frame size).
  --tcp-nodelay                     Turn on tcp-nodelay

Could you further explain/clarify the behavior of "--bounds-multiplier".
We read over the code comments in

trunk/qpid/cpp/src/qpid/client/ConnectionSettings.h

What exactly is the "write queue?"  Based on the code comments, does
bounds allow outgoing frames to be larger than maxFrameSize for the
connection?


    /**
     * The maximum frame size that the client will request for this
     * connection.
     */
    uint16_t maxFrameSize;
    /**
     * Allows the size of outgoing frames to be limited. The value
     * should be a mutliple of the maximum buffer size in use (which
     * is in turn set through the maxFrameSize setting above).
     */
    uint bounds;


Thanks,

Greg





On Tue, 11 Nov 2008, Carl Trieloff wrote:

> "Our analysis leads us to believe that the IPoIB limitations
> seen in our tests are due to the high IPoIB stack overhead.
> We believe that applying modern communication protocols,
> like RDMA, would improve this performance. "
>
> from the report ---  I can confirm this, as the IPoIB driver consumers
> considerable CPU, which RDMA OFED does not.
>
> also, if you want to measure latency, setting
> --max-frame-size
> --tcp-nodely
> --bounds-multiplier
>
> on the client will greatly affect latency
> Carl.
>
>
>


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