[Haskell-cafe] Haskell on a VPS

Jeremy Shaw jeremy at n-heptane.com
Fri Jul 24 22:10:19 EDT 2009

At Thu, 23 Jul 2009 10:53:40 -0400,
John Van Enk wrote:
> Has any one used a service similar to (or equivelant to) Slicehost or
> Linode to run Haskell network applications?

Ok, I discovered an issue with some VPSes. There are two
virtualization technologies in common use, OpenVZ and Xen. With Xen
you can have swap, but with OpenVZ you don't.

In my experience, apps compiled with GHC like to allocate a lot of
virtual memory that they don't really seem to use. With Xen that is
not a big deal, if you allocate memory, but don't actually use it,
that's ok, because in theory it could be swapped out if you actually
did use it.

But with OpenVZ, just allocating the memory counts against your memory
quota, even if you aren't actually using it for anything.

So, in practice, I think you will get a lot more milege out of your
VPS memory if you use Xen instead of OpenVZ, even if you never
*actually* swap to disk on the Xen platform.

There is some more information here:


- jeremy

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