Message-ID: <4C7BCB2E.3090100@2ndquadrant.com>
Date: Mon, 30 Aug 2010 11:15:58 -0400
From: Greg Smith <greg@2ndquadrant.com>
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To: Yeb Havinga <yebhavinga@gmail.com>
CC: Jose Ildefonso Camargo Tolosa <ildefonso.camargo@gmail.com>,
	"pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Subject: Re: Performance on new 64bit server compared to my 32bit
 desktop
References: <4C6CE64D.6070104@edd.fr>	<4C6D76FE.9010407@2ndquadrant.com>
	<E613263E-09D5-4562-BBAF-C72B09883E26@richrelevance.com>
	<4C77F4F4.4020900@2ndquadrant.com>
	<AANLkTikd3BjGD+ti2RBrYu-2WJ7f-QM3dcJLMtYKOZUu@mail.gmail.com>
	<4C7B6498.5040800@gmail.com>
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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