[mpich-discuss] Question to the group about Linux

[Joe Landman]

On 10/25/2010 12:06 PM, Hiatt, Dave M wrote:
> Of the users or ANL personnel who are using Linux, are you using any
> special tools to assist memory allocation? We are trying to add some

There are quite a few tools, in terms of debuggers, profilers, etc.  Not 
entirely on-topic for this list, so if you want to take the conversation 
off list, it might not be a bad idea.

> Linux servers to our test cluster. It is a very memory hungry app, but
> what we are seeing is that the same app on Windows 7 uses about 1/3 the
> space for the same allocations that it uses on RHEL 5.5. We’ve traced

Is hits a 32 bit app on Windows7 and a 64 bit app on RHEL 5.5?

Without knowing any further details, its very hard to have a clue as to 
what is happening.

Next question is: how much memory is the app using on each platform? 
How is it being allocated?


> this to Linux itself. I leap to the conclusion that we’re for sure not
> the first ones to encounter this anomaly. The source code itself is not
> changed between the systems save for a few non material #ifdef ….. #else
> …… #endif statements to address differences in time stamp formats. We
> are compiling with Visual Studio 2008 and VS 2010 from the Windows side
> and Intel C++ 11.1 on the Linux side. As the major memory consumer is
> loaded, on the Linux side memory allocations are dramatically larger, so
> large that they consume about 3.5 times the space that they do in
> Windows. And we observe other anomalies involving how memory is handled
> in Linux. We are new to Linux, so what flavor of Linux are others using,
> are there add on tools that can help mitigate what appear to be very
> inefficient memory allocation characteristics?

Back to how is your code allocating the memory?  Is this in an object 
factory in a deeply nested loop?  The compilers (VS and icc) will 
generate very different code, and call very different helper libs. 
Compiler options matter as much as code design.

Regards,

Joe

>
> Thanks
>
> dave
>
> “With sufficient thrust pigs can fly, but that does not necessarily mean
> it is a good idea”
>
> *Dave M. Hiatt*
>
> Director, Risk Analytics
>
> CitiMortgage
>
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Joseph Landman, Ph.D
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