[gpfsug-discuss] bizarre performance behavior - prefetchThreads
Marc A Kaplan
makaplan at us.ibm.com
Fri Apr 21 13:58:26 BST 2017
Seems counter-logical, but we have testimony that you may need to reduce
the prefetchThreads parameter.
Of all the parameters, that's the one that directly affects prefetching,
so worth trying.
Jan-Frode Myklebust wrote: ...Digging further I found that
reducing prefetchThreads from default=72 to 32 also fixed it, while
leaving maxMBpS at 10000. Can now also read at 3,2 GByte/s....
I can speculate that having prefetchThreads to high may create a
contention situation where more threads causes overall degradation in
system performance.
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