Network RAM revisited

John Burton j.c.burton at gats-inc.com
Wed May 28 11:46:36 EDT 2003



Matt Phillips wrote:
> Hello,
> 
> I guess the main argument against it is why not simply put in more 
> memory sticks and avoid swap altogether. I was told there are 
> applications out there that would still always need swap. To make the 
> case more convincing, I would also like to test performance with real 
> world application traces instead of probablity distributions. Does 
> anyone know of applications (preferably used widespread) for which swap 
> is unavoidable?

In my line of work (atmospheric remote sensing), its not so much a 
matter of "applications for which swap is unavoidable", but "build it 
and they will use it and more" - I don't care how "big" a machine / 
cluster I build, the scientists will find a way to use all its resources 
and ask for more. As I give them more powerful setups, their 
mathematical models increase in size and complexity. Its a constant 
battle to break even. Their models fill the existing memory and start 
hitting swap, which slows their processing down. They need to run faster 
so they can process a day's worth of data in one day, I give them more 
memory. They fill up the additional memory and start hitting swap again, 
but they need it to run faster so... (think you get the picture).

Swap allows them to continually improve / enhance their models. 
Additional memory just makes it go faster.

John

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