Eden space is not empty after a Full GC?

[Neo Jia]

On 5/14/07, Jon Masamitsu <Jon.Masamitsu at sun.com> wrote:
> A perhaps more general case (i.e., no necessarily involving large objects)
> is one where all the live data does not fit into the old generation.  A full
> collection will attempt to compact the young generation into the old
> generation.  If the old generation becomes full during the compaction,
> the remaining live data in the young generation will be compacted
> into the young generation.

Jon,

Thanks. I assume that which objects will be left in the nursery space
is pretty random not based on the ages. Will it improve the
performance if we intend to leave those younger objects in nursery?
Or, just enlarging the mature space to fit in those young objects? But
the
reserved space is almost fully committed.

Thanks,
Neo

>
> Neo Jia wrote:
>
> > On 5/14/07, Y Srinivas Ramakrishna <Y.S.Ramakrishna at sun.com> wrote:
> >
> >>
> >>
> >> Neo Jia wrote On 05/14/07 09:00 AM,:
> >>
> >> > hi,
> >> >
> >> > I just found that for the generational mark-sweep garbage collector,
> >> > after a full GC, the eden space may not be empty.
> >>
> >> That would usually be the case because of  bin-packing
> >> issues with the sliding compaction that might prevent a large
> >> object in Eden from being "slid" into the available space
> >> in old gen or in the survivor space. It'll usually be the case
> >> then that your are running with memory quite tight (or
> >> with a huge Eden and very large objects).
> >
> >
> > Could you point me to the code where the full GC found it cannot slide
> > this huge chunk?
> >
> > Thanks,
> > Neo
> >
> >>
> >> Are there other situations where you see a non-empty Eden
> >> following a mark-compact full collection?
> >>
> >> >
> >> > Is there any implementation concern for this? Can I force the full GC
> >> > to clean the eden space?
> >>
> >>
> >> A full gc would do a mark-compact collection.
> >>
> >> -- ramki.
> >>
> >> >
> >> > Thanks,
> >> > Neo
> >>
> >>
> >> --
> >>
> >> ----------------------------------------------------------------------------
> >>
> >> Y. Srinivas Ramakrishna               HotSpot JVM
> >> Sun Microsystems, Inc., USCA 22-123   CSG / Sun Software
> >> 4220 Network Circle                   408 276 7250 (x17250)
> >> Santa Clara, CA  95054, U.S.A.        Y dot S dot Ramakrishna at Sun
> >> dot COM
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