# Re: JRuby performance questions answered

**URL:** <https://www.ruby-forum.com/t/re-jruby-performance-questions-answered/143539>\
**Category:** Ruby\
**Created:** [July 20, 2008, 6:20am UTC](https://www.ruby-forum.com/t/re-jruby-performance-questions-answered/143539 "2008-07-20T06:20:16Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![unknown](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/u/4bbf92/32.png) [@unknown](https://www.ruby-forum.com/u/unknown)\
**Post date:** [July 20, 2008, 6:20am UTC](https://www.ruby-forum.com/t/re-jruby-performance-questions-answered/143539/1 "2008-07-20T06:20:16Z")

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Roger P. wrote:

> Rick Denatale wrote:
> 
> > Roger, you REALLY need to read the literature on GC which has been  
> > accumulating for the past 50 years.
> > 
> > Reference counting is pretty much an obsolete approach to GC. It was  
> > probably the first approach taken for lisp back in the 1950s. Other  
> > language implementations usually started with reference counting (e.g.  
> > the first Smalltalk).

[snip]

I spent a good bit of time the other day downloading some of this  
“literature”. From a theoretical computer science perspective, it can  
be shown that all garbage collection schemes are equivalent in a broad  
sense. And when you benchmark them, all of them have strengths and  
weaknesses that are workload-dependent.

And IIRC the first Lisp garbage collector was pure mark-and-sweep. I  
forget where reference counting was first used – maybe Snobol. And  
stop-and-copy was also developed very early, maybe for Scheme. All  
three of them are quite simple to understand, once you’ve bitten the  
bullet and learned recursion. 🙂

> This is somewhat confusing for me, because it seems that using a  
> mark and sweep generational style GC slows down Ruby, as per
> 
> Matz’s observations: [Question on bottleneck of ruby - Ruby - Ruby-Forum](http://www.ruby-forum.com/topic/123747)

At a higher level, if you are doing a lot of garbage collection, you  
need to look at your algorithms. And you need to supply a large enough  
working set of real memory before you go finger-pointing at the  
garbage collector, regardless of its type. There are some pretty good  
web sites out there that have, via profiling, made some tremendous  
improvements in Rails performance this way.

> I suppose I’m just naive, but it doesn’t seem clear to me which is  
> the ‘best’ GC style, from the above observations. There appears to  
> be no clear answer.

That’s because it’s workload-dependent. What’s worse, overall  
performance on “modern” architectures is highly dependent on spatial  
and temporal locality in your interpreter, whether it’s method  
dispatch, garbage collection, regular expression processing, bignum  
operations, etc. It’s not just garbage collection by any stretch of  
the imagination. That’s why I profile Ruby interpreters. 🙂

–  
M. Edward (Ed) Borasky  
[http://pdxfoscon.org/start/](http://pdxfoscon.org/start/)  
[http://ruby-perspectives.blogspot.com/](http://ruby-perspectives.blogspot.com/)

“A mathematician is a machine for turning coffee into theorems.” –  
Alfréd Rényi via Paul Erd?s

M. Edward (Ed) Borasky [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)