i386 vs amd64 - benchmark results

Vivek Khera vivek at khera.org
Wed Jul 27 15:52:32 GMT 2005

On Jul 26, 2005, at 1:57 PM, Martin wrote:

> Please notice the memory speed penalties while the
> system is running on amd64 kernel. I would like to
> know what causes this kind of low performance when
> memory is being accessed.

The amd64 memory architecture is NUMA -- that is, depending on  how  
your RAM is layed out, some of it is faster to access for each  
processor.  Accessing RAM "local" to the other processor(s) is slower.

There are many subtle issues relating to non-uniform memory access  
and how to code programs to take advantage of it (or try to avoid  
being bit by it).  It is a very hard problem, and the three letters  
following my name came to be from researching this issue 11 years  
ago :-)

The FreeBSD scheduler and memory allocators are definitely not NUMA  

Vivek Khera, Ph.D.
+1-301-869-4449 x806

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