GC leaks debugging

Boehm, Hans hans.boehm@hp.com
Sat Apr 2 00:27:00 GMT 2011


> -----Original Message-----
> From: java-owner@gcc.gnu.org Andrew Haley
> Sent: Friday, April 01, 2011 2:34 AM
> To: java@gcc.gnu.org
> Subject: Re: GC leaks debugging
> 
> On 04/01/2011 10:02 AM, Erik Groeneveld wrote:
> > On Fri, Apr 1, 2011 at 10:45, Andrew Haley <aph@redhat.com> wrote:
> >> On 01/04/11 09:39, Erik Groeneveld wrote:
> >>> From reading about the
> >>> GC, I understand that the GC knows what is a pointer and what not
> >>> because there is type information associated with the Java objects.
> >>> So I'd expect no black-listing at all.  It that a right
> observation?
> >>
> >> No.  Objects are scanned precisely, but the stack is not.
> >
> > Thanks.  I think I can rule the stack out by reviewing/adapting my
> > test program.  I'll do that first.
> >
> >> Also, depending
> >> on your compilation options, the data segments of your program may
> be
> >> scanned conservatively.
> >
> > I have to think about this one.  Which options are you thinking of?
> 
> -findirect-dispatch
> 
> With that option, everything except the stack is scanned precisely.
> However,
> there is some runtime overhead.
> 
> Andrew.
Note that in the information you posted, the GC was scanning around 7.5MB of roots conservatively.  It might be worth checking what those regions are.

The number of black-listed pages seems really high to me.  Is the collector configured for too small a heap?

What's the platform?


Hans



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