Re: [rvm-research] Slots and Object Barriers

On 26/06/2009, at 8:14 PM, Cristian Perfumo wrote:

> I notice that if they are set to true, the applications go faster in
> general. I was wondering what the tradeoff is, if any, between
> having them set to true and false.

Over the weekend I ran a pretty exhaustive performance comparison on
two platforms.   These results suggest that overall, there's nothing
in it (at least on average over a decent set of benchmarks...)

DaCapo, jvm98 & jbb2005 each run at 2 X minimum heap size. "AA" ->
aastore, "PF" -> putfield

Machine 1.   Intel i7.
       Total time:
               http://cs.anu.edu.au/~Steve.Blackburn/private/results/jikesrvm-performance-2009/i7-barriers/time.all.html
       Mutator:
               http://cs.anu.edu.au/~Steve.Blackburn/private/results/jikesrvm-performance-2009/i7-barriers/time.mu.all.html
       GC
               http://cs.anu.edu.au/~Steve.Blackburn/private/results/jikesrvm-performance-2009/i7-barriers/time.gc.all.html

Machine 2.   Intel Core 2 Quad.
       Total time:
               http://cs.anu.edu.au/~Steve.Blackburn/private/results/jikesrvm-performance-2009/c2q-barriers/time.all.html
       Mutator:
               http://cs.anu.edu.au/~Steve.Blackburn/private/results/jikesrvm-performance-2009/c2q-barriers/time.mu.all.html
       GC
               http://cs.anu.edu.au/~Steve.Blackburn/private/results/jikesrvm-performance-2009/c2q-barriers/time.gc.all.html

I also have data for a 3 X heap size, and it is almost identical.

I hope that helps your understanding of the tradeoffs.   It was a
useful exercise for me because it re-confirms that what we have got as
our defaults is reasonable, at least for these two architectures.

Cheers,

--Steve

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