CMS large objects vs G1 humongous allocations

[Amit Balode]

Hi Thomas, thanks for input.

For "Every time this happens, the young gen is really large, however it
seems that according to heap size calculations the surviving objects should
actually have enough space." - Could you paste the snippet from log which
you referring to?

"I remember discussing this or similar issues in the past, not sure if it
has been fixed in one way or another in the meantime." It would really be
great if you could help dig whether it has been fixed and which release so
we could try upgrading to it.

good point regarding G1MaxNewSizePercent. In general,  I have been trying
to avoid too many customization with G1 and let heuristics decide for
itself but if no option, I will try to put this setting and experiment.

On Wed, Feb 1, 2017 at 6:40 PM, Thomas Schatzl <thomas.schatzl at oracle.com>
wrote:

> Hi Amit,
>
> On Tue, 2017-01-31 at 22:04 +0530, Amit Balode wrote:
> > File is a bit huge:) linked it here https://raw.githubusercontent.com
> > /amitbalode/uploads/master/amit.txt
> >
>
>   some observations:
>
> - some humongous objects; not sure if increasing heap region size helps
> - as for the evacuation failures, I think they can be avoided by
> capping the maximum young gen size. Every time this happens, the young
> gen is really large, however it seems that according to heap size
> calculations the surviving objects should actually have enough space.
> It does not because the humongous objects may take up too much space,
> and at least the printing does not take that into account.
>
> I remember discussing this or similar issues in the past, not sure if
> it has been fixed in one way or another in the meantime.
>
> Anyway, capping young gen should be able to avoid this issue at least
> some times. Try setting -XX:G1MaxNewSizePercent to something lower than
> the default 60%.
>
> Thanks,
>   Thomas
>
>


-- 
Thanks & Regards,
Amit.Balode
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.openjdk.java.net/pipermail/hotspot-gc-use/attachments/20170201/0d20d2e4/attachment.html>