Yeb Havinga wrote:
> model name : AMD Phenom(tm) II X4 940 Processor @ 3.00GHz
> cpu cores : 4
> stream compiled with -O3
> Function Rate (MB/s) Avg time Min time Max time
> Triad: 5395.1815 0.0089 0.0089 0.0089
For comparison sake, an only moderately expensive desktop Intel CPU
using DDR3-1600:
model name : Intel(R) Core(TM) i7 CPU 860 @ 2.80GHz
cpu cores : 4
siblings : 8
Number of Threads requested = 4
Function Rate (MB/s) Avg time Min time Max time
Triad: 13666.0986 0.0108 0.0107 0.0108
8 hyper-threaded cores here. They work well for improving CPU-heavy
tasks, but with 4 threads total is where the memory throughput maxes out at.
I'm not sure if Yeb's stream was compiled to use MPI correctly though,
because I'm not seeing "Number of Threads" in his results. Here's what
works for me:
gcc -O3 -fopenmp stream.c -o stream
And then you can set:
export OMP_NUM_THREADS=4
Or whatever you want in order to control the number of threads it uses
inside. Here's the way scaling works on my processor:
Number of Threads requested = 1
Function Rate (MB/s) Avg time Min time Max time
Triad: 9806.2648 0.0150 0.0149 0.0151
Number of Threads requested = 2
Function Rate (MB/s) Avg time Min time Max time
Triad: 12495.2113 0.0117 0.0117 0.0118
Number of Threads requested = 3
Function Rate (MB/s) Avg time Min time Max time
Triad: 13388.7187 0.0111 0.0109 0.0126
Number of Threads requested = 4
Function Rate (MB/s) Avg time Min time Max time
Triad: 13695.6611 0.0107 0.0107 0.0108
Number of Threads requested = 5
Function Rate (MB/s) Avg time Min time Max time
Triad: 12651.7200 0.0116 0.0116 0.0116
Number of Threads requested = 6
Function Rate (MB/s) Avg time Min time Max time
Triad: 12804.7192 0.0115 0.0114 0.0117
Number of Threads requested = 7
Function Rate (MB/s) Avg time Min time Max time
Triad: 12670.2525 0.0116 0.0116 0.0117
Number of Threads requested = 8
Function Rate (MB/s) Avg time Min time Max time
Triad: 12468.5739 0.0119 0.0117 0.0131
--
Greg Smith 2ndQuadrant US Baltimore, MD
PostgreSQL Training, Services and Support
greg@2ndQuadrant.com www.2ndQuadrant.us
