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From Brad Sarsfield <b...@bing.com>
Subject RE: HyperThreading in TaskTracker nodes?
Date Tue, 05 Feb 2013 18:03:46 GMT
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.


-----Original Message-----
From: Terry Healy [mailto:thealy@bnl.gov] 
Sent: Tuesday, February 5, 2013 7:20 AM
To: user@hadoop.apache.org
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.



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