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MapReduce >> mail # user >> RE: HyperThreading in TaskTracker nodes?


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RE: HyperThreading in TaskTracker nodes?
Hate to say it, but HyperThreading can have either positive or negative performance characteristics.  It all depends on your workload.  You have to measure very careful; it may not even be a bottleneck(!) :)

I hit a pretty significant power issue when I enable HyperThreading at multi-thousand node scale.  We hit a ~8-10% power utilization increase, which, if rolled out to the entire cluster, would put me a few %'ge over our max spec power. In this case, for our workload, we actually saw a 15% increase in processing throughput / job latency.   We ended up literally turning off machines and enabling HyperThreading on the remaining and saw an overall ~10% efficiency gain in the cluster, with a few less machines, but running hot on power.

~Brad

-----Original Message-----
From: Terry Healy [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, February 5, 2013 7:20 AM
To: [EMAIL PROTECTED]
Subject: HyperThreading in TaskTracker nodes?

I would like to get some opinions / recommendations about the pros and cons of enabling HyperThreading on TaskTracker nodes. Presumably memory could be an issue, but is there anything to be gained, perhaps because of I/O wait? My small cluster is made of relatively slow and old systems, which mostly are quite slow to/from disk, if that matters.

Thanks,

Terry

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Todd Lipcon 2013-02-05, 21:09