[gclist] gc concerns

Fergus Henderson fjh@cs.mu.oz.au
Thu, 14 Dec 2000 10:44:31 +1100

On 13-Dec-2000, Manoj Plakal <plakal@cs.wisc.edu> wrote:
> Boehm, Hans wrote (Wed, Dec 13, 2000 at 11:13:48AM -0800) :
> > 1) Most modern computers are memory-poor in comparison to the processor
> > speed.  Hence there is strong motivation to keep heap sizes down, and thus
> > most applications run with heap sizes that are small enough that
> > stop-the-world collections finish in a reasonable amount of time, and GC
> > pause times are often not much of an issue.
> 	This may be true for a desktop or workstation but I'm
> 	not sure this applies to servers. They seem to be
> 	loaded with gigabytes of RAM these days.

I think Hans meant memory *speed* is poor in comparison to processor
speed.  Even though computers may have gigabytes of RAM, there's still
a strong incentive to keep heap sizes down, since you'll get better
locality and hence better cache performance.

So, suppose you have a 4-CPU system, with each one being say a 1GHz
Pentium III, and you want GC pause times of no more than 1/3 of a second.
How big can your heap be?

Fergus Henderson <fjh@cs.mu.oz.au>  |  "I have always known that the pursuit
                                    |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.