[Haskell-cafe] OS swapping and haskell data structures

[Duncan Coutts]

On Wed, 2007-08-01 at 11:31 -0700, Bryan O'Sullivan wrote:
> Alex Jacobson wrote:
> > If you create a Data.Map or Data.Set larger than fits in physical 
> > memory, will OS level swapping enable your app to behave reasonably or 
> > will things just die catastrophically as you hit a memory limit?
> 
> Relying on the OS to page portions of your app in and out should always 
> be the fallback of last resort.  You are fairly guaranteed to get 
> terrible performance because the VM subsystem can't anticipate your 
> app's memory access patterns, and catastrophic death of either your app 
> or other system processes is a strong possibility (Google for "OOM 
> killer" if you want some horror stories).  In many cases, you can't even 
> rely on paging being possible.

Furthermore, as I understand it, GC does not interact well with paging
since the GC has to traverse the data structures on major GCs it'll
force it all to be kept in memory.

Duncan