RFR (S): 8131734: Add free_archive_regions support to G1 for -Xshared:auto
thomas.schatzl at oracle.com
Thu Aug 6 07:48:49 UTC 2015
On Wed, 2015-08-05 at 16:42 -0400, Tom Benson wrote:
> Thanks, Kim.
> On 8/5/2015 3:27 PM, Kim Barrett wrote:
> > On Aug 5, 2015, at 3:21 PM, Tom Benson <tom.benson at oracle.com> wrote:
> >> Hi,
> >> Updated full and incremental webrevs are at:
> >> http://cr.openjdk.java.net/~tbenson/8131734/webrev.01/
> >> http://cr.openjdk.java.net/~tbenson/8131734/webrev.01.vs.00/
> > Looks good.
Looking again at the code starting from line 1144 with the comment,
there may still be an issue here: consider a VM A having 8M regions 1,
2, and 3, each spanning 8M (see figure below; each letter represents 1M
of space), and a mapping from a VM B with 2M region size with the
following layout that is loaded into VM A and failed.
1 2 3 region#
AAAAAAAA AAAAAAAA AAAAAAAA VM A regions (8M region size)
BB BB BBBBBBBB BBBB VM B mapping (2M region size)
E.g. the mapping is from 2-3M, and another mapping from 6-20M. E.g. the
ranges array contains
(2, 3), (6, 20)
now, after freeing region 1 from the first mapping (2, 3), start_region
of the second mapping (=1) equals prev_last_region (=1); now the cursor
is advanced to the region of the end of the second mapping (=3),
forgetting to free region 2.
What am I missing here?
Thanks for adding the initialization checks.
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