IEEE Spectrum November, 2016 - 17

intel

iT'S geTTing crowded: This Intel HaswellEX Xeon E7 V3 processor has 18 cores trying to
work together without messing up one another's
calculations. A bit of additional hardware could
speed up communication among the cores.

packet processing-like network nodes
do on the Internet-by a greater and
greater amount the more cores were
involved. For 16 cores, QMD worked 20
times as fast as the software could.
Once they achieved this result, the
engineers reasoned that the QMD might

be able to do a few other tricks-such as
turning more software into hardware.
They added more logic to the QMD and
found it could speed up several other
core-communications-dependent functions, including MapReduce, a technology Google pioneered for distributing
work to different cores and collecting
the results.
Srini Devadas, an expert in cache
control systems at MIT, says the QMD
addresses "a very important problem."
Devadas's own solution for the use of
caches by multiple cores-or even multiple processors-is more radical than
the QMD. Called Tardis, it's a complete
rewrite of the cache management rules,
and so it is a solution aimed at processors and systems of processors further in
the future. But QMD, Devadas says, has
nearer-term potential. "It's the kind of
work that would motivate Intel-putting

in a small piece of hardware for a significant improvement."
The Intel engineers involved couldn't
comment on whether QMD would find
its way into future processors. However, they are actively researching its
potential. (Wang is now a research scientist at Intel.) The engineers hope that
QMD, among other extensions of the
concept, can simplify communication
among the cores and the CPU's input/
output system.
Solihin, meanwhile, is inventing
other types of hardware accelerators.
"We have to improve performance by
improving energy efficiency. The only
way to do that is to move some software
to hardware. The challenge is to figure
out which software is used frequently
enough that we could justify implementing it in hardware," he says. "There is
a sweet spot." -Sa muel k. mooR e

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Table of Contents for the Digital Edition of IEEE Spectrum November, 2016

IEEE Spectrum November, 2016 - Cover1
IEEE Spectrum November, 2016 - Cover2
IEEE Spectrum November, 2016 - 1
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IEEE Spectrum November, 2016 - Cover3
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