On 16 December 2005 10:05, Joel Reymont wrote:

I'm trying to restrict GHC to 800Mb of heap at runtime by passing in +RTS -M800M, the machine has 1Gb of memory and top shows free physical memory dropping below 175Mb. I suppose I'm missing something obvious or paying attention to the wrong statistics, Unix has a good VM manager after all. Are my runtime options correct, though?

-M800m should do more or less the right thing, but it is possible for GHC to exceed this figure by a small percentage. Rather than considering the "worst case" requirements for the next GC, GHC uses a more "average case" estimate, which sometimes ends up being wrong, but in most cases results in better utilisation of the available memory. Cheers, Simon