Dear Task Force Members,
Please excuse my mental typo at the beginning of that message.
(Task Force, Task Force, Task Force).
:)
Dan
On 1/4/13 3:56 PM, Daniel Dove wrote:
Dear Study Group Participants,
A question that has lingered in my mind relates to the additional
latency of FEC as it would affect HPC and distributed computing
performance in short-reach optical applications. While we can
clearly understand the impact of FEC on BER, and we can assess
various approaches and their impact on latency, what has been
lacking is detail on the impact of latency to real-world compute
applications.
I recently discovered a performance presentation at the HPC
Advisory Council that is focused on comparing two particular
compute platforms over a variable set of compute nodes, but what
would be really interesting is to see a single compute platform
and the effect strictly of channel latency on the performance.
Capturing the impact of various channel latencies over the number
of nodes would also be of interest.
Specifically, imagine slide 7 with a single compute platform and
multiple bars (one for each latency value) per node-count. Use
latency values of 10ns, 100ns, 1uS for example which could be
created by using longer fibers between nodes.
I understand that different applications will have different
levels of sensitivity, so using industry benchmarks seems like an
appropriate way to assess the impact on performance. It would
allow end users to evaluate the effect of link distances and other
sources of latency such as FEC on overall compute performance.
This message is a request for contribution in this area. It would
be very helpful to the Task Force to understand the tradeoffs we
are making between cost, complexity, and performance. If someone
has an alternative assessment that draws out the impact of link
latency on distributed compute performance, please feel free to
share.
Best Regards,
--
Dan Dove
Chair, P802.3bm
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