On 28/02/2012 15:59, Johan Tibell wrote:
On Tue, Feb 28, 2012 at 12:57 AM, Simon Marlow<[email protected]> wrote:
Ah, so I see where your confusion arises - this assumption is not true in
general. Just discard the assumption, and I think everything will make more
sense.
Picking a size for -A around the L2 cache is often a good idea, but not
always. GHC defaults to -A512K, but programs that benefit from much larger
sizes are quite common. For more about the tradeoff, see my SO answer here:
http://stackoverflow.com/questions/3171922/ghcs-rts-options-for-garbage-collection/3172704#3172704
Thanks for the explanation.
One has to be very careful in selecting the size of the allocation
area in benchmarks. If the allocation area is large enough the GC
might not need to run at all for the duration of the benchmark, while
in a real program it would run.
It is a problem, yes. You also have to be careful when comparing two
benchmarks runs that one didn't do an extra GC, because that can skew
the results against it.
I'm fairly sure the GC community have looked into this problem, but I
don't know of any references off hand. Trawling Richard Jones' GC
bibliography might turn up something:
http://www.cs.kent.ac.uk/people/staff/rej/gcbib/
Cheers,
Simon
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