[Haskell-cafe] +RTS -M800M

Simon Marlow simonmar at microsoft.com
Fri Dec 16 06:51:12 EST 2005

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.


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