[OSM-talk] OSM-to-PostGIS issues

[Gerald A]

Hi Juan,

On Mon, Jul 19, 2010 at 12:18 PM, Juan Lucas Domínguez Rubio <
juan_lucas_dr at yahoo.com> wrote:

> Hello,
> Are you taking into account Windows XP's virtual memory (4 GB, I think)?
> I meant 1.5 GB of physical memory.
>

I'm pretty sure they were talking about physical memory.

Using virtual memory helps with some things, but recall how it works -- it
is using your had disk to offload physical memory.
Every time you dip into that mechanism, something in physical RAM has to be
written to disk, then something else has to be
read from disk into RAM. So, you incur 2 very slow (from RAM/CPU point of
view) operations. With a memory footprint of 4GB,
your 1.5 is more then twice overcommited (almost 3x). That means the process
I described above will happen quite often,
if not constantly. This is called swapping, and can take something that
should take a few seconds and make it last minutes.

If the overall operation is supposed to last 5-10 minutes, it can be hours.
I think you see the point here.

With RAM prices so inexpensive, if you are looking to work on this data on
an ongoing basis, it makes sense to upgrade. (If
this is a one-shot deal, see if you can rent/borrow a box with the requisite
amount of RAM). You'll be much happier with the
results on a machine with adequate RAM.

Thanks,
Gerald.
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