Re: [rvm-research] Small Code Space

+1. We ran into one of these performance anomalies when code and data were
intermingled a long time ago. It was pretty mystifying -- running
experiments in my directory on the same machine was significantly faster
than running it in the grad student's directory (different length of
environment = different code offsets = cache conflicts for him but not for
me). We resolved this by separating out the code and data for our MC^2
paper in OOPSLA 2004 (p.89-90) --
http://dl.acm.org/citation.cfm?doid=1035292.1028984 -- and Dave is so right
-- no one should have to waste time dealing with that sort of thing :).








--
Professor Emery Berger
School of Computer Science
University of Massachusetts, Amherst
www.cs.umass.edu/~emery


On Mon, Apr 21, 2014 at 2:10 PM, David P Grove <[email protected]> wrote:

>  Nathan Ricci <[email protected]> wrote on 04/16/2014 02:42:09 PM:
>
> >
> >    I was wondering what is actually allocated in the small code
> > space? And are objects allocated there handled any differently than
> > those in any other MarkSweepSpace?
> >
>
> Hi,
>
>  The actual machine instructions (JITed code) for most methods (those that
> are not "too big", which go in a large code space).
>
>  You can find the original motivation and experiments for a separate code
> space described here: http://dx.doi.org/10.1145/1133956.1133980
>
>  The life time of code tends to be longer than many small objects, so
> there are some minor benefits to segregating it.  The main benefit though
> is to separate code from data to avoid stumbling over odd/annoying
> micro-architectural "features" that can cause performance lost when code
> and data is tightly intermixed.
>
> --dave
>
>
>
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