Question on GCJ/Boehm Memory Utilization, Part II

Craig Vanderborgh
Thu Feb 23 21:00:00 GMT 2006

> ----- Original Message -----
> From: "Martin Egholm Nielsen" <>
> To:
> Subject:  Re: Question on GCJ/Boehm Memory Utilization, Part II
> Date:  Thu, 23 Feb 2006 20:49:25 +0100
> >> As Martin pointed out, adjusting GC_free_space_divisor should help.
> --- 8< 8< 8< ---
> > The Boehm heap on our embedded application is now less than half 
> > the size it was before this find.  And the reason is obvious.  
> > Now, the parsed token strings are usually 88 characters, instead 
> > of 12932.  This, as one would expect, greatly affects the 
> > behavior of the collector in the positive direction.  The reason 
> > I'm reporting this in so much detail is that I'm hoping I can 
> > help others who have this problem save a few years of their time.
> Really nice!
> But may I suggest you to try increasing the 
> GC_free_space_divisor... Doing that I also decreased my heap size 
> by more than 50%!
> You could try the extreme and set it to 20, just to see what to 
> expect approx. for maximum gain...

Hello Martin!

We are already running with GC_free_space_divisor set to 20 in our GCJ build, as you suggested this the last time we were whacked by one of these memory allocation problems.  But I am curious - can we expect unpleasant side-effects if we have this parameter set to the "extreme"?  What do you thing about this?  Is this parameter a subject for a tuning study, or are there some rules of thumb that can be used to guesstimate the best value?

Thanks in advance,
craig vanderborgh
voxware incorporated

> // Martin


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