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From Andre Van Klaveren <>
Subject Re: OutOfMemoryError - 100 thread limit?
Date Wed, 27 Apr 2005 14:13:08 GMT
We're battling this same problem at our client's site.  I think I've
identified the same cause (running out of Perm Gen space) but I have
to prove it to them first.  Hooking a profiler into the Tomcat
instance should clearly show this but they don't have one handy. 
Moving some of the applications to a second instance of Tomcat should
also solve this problem.

Andre Van Klaveren
Architect III, SCP
Enterprise Transformation Services
Unisys Corporation

On 4/21/05, Caldarale, Charles R <> wrote:
> > From: Peter Lin []
> > Subject: Re: OutOfMemoryError - 100 thread limit?
> >
> > the default Perm is 64M. If LeeAnn's webapp have a large number of
> > classes, maybe there's too many; therefore forcing the VM to resize
> > the perm.
> IIRC (haven't looked at core HotSpot code in detail since 1.4.1 days),
> the virtual address boundary between perm and the other generations is
> fixed at JVM initialization and never moves.  The perm gen does go
> through GC just like the other gens, but no memory ever moves between
> the perm and any other space, and the perm gen maximum virtual address
> range never changes.
> The HotSpot JVM allocates, but does not commit, all of the -Xmx space at
> startup in one contiguous block (although there were rumors of that
> changing in later JVMs).  Only the -Xms portion is committed, split up
> into three regions - young, old, and perm.  When a region fills and GC
> doesn't reduce the usage significantly, additional pages are committed
> in whichever region needs expanding.
> I think what was happening is that LeeAnn simply had more classes than
> would fit in 64 MB.  Nothing to do with threads, just the total number
> of classes in all the applications added together.
>  - Chuck
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