Current heap layout of generational mark-sweep GC

[Neo Jia]

On 5/16/07, Jon Masamitsu <Jon.Masamitsu at sun.com> wrote:
>
>
> Neo Jia wrote:
>
> > On 5/15/07, Jon Masamitsu <Jon.Masamitsu at sun.com> wrote:
> >
> >> Regarding "PrintMallocFree" it is broken in the sense that not
> >> all malloc()/free() calls are wrapped inside the corresponding
> >> AllocateHeap()/FreeHeap().  I've used it maybe once.   I don't
> >> know what to say about why it's gone stale.
> >
> >
> > Jon,
> >
> > Not only not catching all the malloc/free but also crashing the strlen
> > function on JDK7. This is what I found several days before.
>
>
> Well that's bad.  Does running just anything with "PrintMallocFree"
> cause this crash?

Jon,

I just submit a patch for this problem to the runtime mailing list.

http://thread.gmane.org/gmane.comp.java.openjdk.hotspot.runtime.devel/37

Thanks,
Neo

>
> >
> > So, is GC people in charge of detecting memory leak? Because after
> > running valgrind with hotspot, it reports lots memory lost.
>
>
> No, each group (GC, runtime, compilers, and serviceability)
> manages its own usage of the CHeap with regard to leaks.
>
> >
> > Thanks,
> > Neo
> >
> >
> >>
> >> Neo Jia wrote:
> >>
> >> > On 5/14/07, Jon Masamitsu <Jon.Masamitsu at sun.com> wrote:
> >> >
> >> >> Neo,
> >> >>
> >> >> If by "generational mark-sweep GC" you mean the UseSerialGC
> >> >> or UseParNewGC,
> >> >
> >> >
> >> > I mean the UseSerialGC.
> >> >
> >> >  yes the storage you listed are the major
> >> >
> >> >> pieces that we allocate in the CHeap.   There are many smaller
> >> >> data structures that are allocated out of the CHeap.  For example,
> >> >> performance counters are CHeap allocated.  Or just the storage
> >> >> for various subclasses of Generation that the GC uses.
> >> >>
> >> >> I believe the largest piece of the CHeap that the compilers
> >> >> use is the CodeCache and it is allocated before the Java
> >> >> heap is allocated.
> >> >
> >> >
> >> > The current "PrintMallocFree" seems broken already. Do you still use
> >> > this to check the
> >> > CHeap usage?
> >> >
> >> > Thanks,
> >> > Neo
> >> >
> >> >>
> >> >> Jon
> >> >>
> >> >> Neo Jia wrote:
> >> >>
> >> >> > On 5/14/07, Jon Masamitsu <Jon.Masamitsu at sun.com> wrote:
> >> >> >
> >> >> >> Neo,
> >> >> >>
> >> >> >> Are you asking specifically about CHeap usage by the
> >> >> >> garbage collector (i.e., you're not interested in the
> >> >> >> compiler's use CHeap space)?
> >> >> >
> >> >> >
> >> >> > Jon,
> >> >> >
> >> >> > Although my question is about the CHeap usage by GC, I am also
> >> >> interested
> >> >> > in knowing the CHeap space usage of compiler.
> >> >> >
> >> >> > Thanks,
> >> >> > Neo
> >> >> >
> >> >> >>
> >> >> >> Jon
> >> >> >>
> >> >> >>
> >> >> >> Neo Jia wrote:
> >> >> >>
> >> >> >> > hi,
> >> >> >> >
> >> >> >> > I am wondering that for the generational mark-sweep GC, if the
> >> >> block
> >> >> >> > offset shared array is the last allocated object on the CHeap.
> >> >> >> >
> >> >> >> > The following is my understanding of the current heap layout:
> >> >> >> >
> >> >> >> > 1. The nursery space is on the lowest address
> >> >> >> > 2. The mature space is following the nursery address.
> >> >> >> > 3. The permanent space is following the nursery address at a
> >> higher
> >> >> >> > address.
> >> >> >> > 4. The card table is allocated from the end of the permanent
> >> space,
> >> >> >> > the regions inside it will be mapped to these previous three
> >> spaces
> >> >> >> > sequentially, from lower address to higher address.
> >> >> >> > 5. The block offset shared array used by the mature space
> >> will be
> >> >> >> > allocated at the end of the card table area, which is used by
> >> >> mature
> >> >> >> > space. And the virtual space size of this area will be set
> >> >> according
> >> >> >> > to the mature space and word bits.
> >> >> >> >
> >> >> >> > So, is there any space allocated following?
> >> >> >> >
> >> >> >> > Thanks,
> >> >> >> > Neo
> >> >> >>
> >> >> >>
> >> >> >
> >> >> >
> >> >>
> >> >
> >> >
> >>
> >
> >
>


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