On 03/18/2012 12:02 PM, Richard Pieri wrote: > What you will typically find is that if your threads are CPU bound then you > will see better performance over the long term with HT disabled. The reason > is that the phantom CPUs that HT provides need to share cache and memory > bandwidth and there is some extra switching overhead. The upshot is that if > you have 1 CPU with 2 HT threads and 4 CPU-bound jobs to run, the total time > to run all 4 jobs will be less with HT disabled. As an aside for anyone > running a Condor pool, disabling HT is recommended for this reason. > > On the other hand, if you are not CPU-bound across all of your threads, or in > environments where concurrency is more important than throughput, then HT may > be a win. > > AMD's Bulldozer architecture has less resource contention than Intel's HT > implementations (less overhead) but two threads on 1 core still have to share > some resources and you will usually see results similar to what I described. In Toronto they always turn off HT. I ran a quick test and found that the RiskWatch application runs better with no HT. There is certainly some benefit to HT under some circumstances.
-- Jerry Feldman <g...@blu.org> Boston Linux and Unix PGP key id:3BC1EB90 PGP Key fingerprint: 49E2 C52A FC5A A31F 8D66 C0AF 7CEA 30FC 3BC1 EB90
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