profile not showing it all?

Niels van der Velden cpjvelde at
Mon Sep 12 08:04:49 EDT 2005

Simon Marlow wrote:
>   - overhead of profiling itself, which currently runs at 2 extra
>     words per heap object.  At a guess, that probably results in
>     about a 30% overhead.
top also shows 161mb for the non-profiling binary (the same as the
profiling binary). This strikes me as odd, because the profiling binary
*should* take more memory (because of all the reasons mentioned in this

>   - generational garbage collection.  A major GC in the standard
>     copying collector will usually require 3L bytes of memory, where
>     L is the amount of live data.  This is because by default (see the
>     +RTS -F option) we allow the old generation to grow to twice its
>     size (2L) before collecting it, and we require additionally L bytes
>     to copy the live data into.  When using compacting collection, this
>     is reduced to 2L, and can further be reduced by tweaking the -F
>     option.  Additionally the allocation area (generation 0) takes 512Kb
>     by default.
with -c, top records 149mb max (it just grows more gradually)
and without -c, top records 161 max.

I used the -B setting to sound a bell at the beginning of a major GC, so
i could relate the memory growth showing up in top to the start of a GC.
However, im not hearing anything (also -t, which should show GC stats
after running the program, is not showing anything). Does this mean
there was no GC ?


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