Thanks for taking a look at this!
StefanK
On 2019-02-14 10:58, Erik Österlund wrote:
Hi Stefan,
I think this makes things better. I like the cleanups and I like the
partial support for heap parsing. I think we should bring this in, and
it looks good to me.
Of course we can always improve this further at some point in the future
to deal with broken Klass pointers better.
Thanks,
/Erik
On 2019-02-13 15:52, Stefan Karlsson wrote:
Hi all,
Please review / comment on this patch to enable a best-effort live
heap region iteration implementation in ZGC.
http://cr.openjdk.java.net/~stefank/8218922/webrev.01/
https://bugs.openjdk.java.net/browse/JDK-8218922
The SA has functionally that relies on live heap region information
from the GCs. This is problematic when dead objects are left in the
heap, and their classes have been unloaded.
Because of this ZGC has so far not implemented this feature. However,
we could provide a best-effort implementation that most likely will
work if classes are not unloaded (or class unloading is turned off),
and otherwise might fail to fully parse and report all live heap regions.
For active, non-relocating pages the patch simply returns [start, top)
and for pages being actively relocated, it reports regions containing
the non-forwarded objects, the other objects are either dead or could
be found in one of the to-regions.
With this patch I'm able to get heap histograms with ZGC.
Maybe this is enough to enable a bit more SA debugging capabilities
when running with ZGC? What do you think, should we bring in this change?
To be able to implement this more cleanly I've restructured the live
region collection, and pushed GC specific code into the specific GCs.
There are some extra usage of generics to make the code a bit easier
to read and develop.
Thanks,
StefanK
