G1-GC - Full GC [humongous allocation request failed]

[Vitaly Davidovich]

Hi Jenny,

On Fri, Oct 7, 2016 at 11:52 AM, yu.zhang at oracle.com <yu.zhang at oracle.com>
wrote:

> Prasanna,
>
> In addition to what Vitaly said, I have some comments about your question:
>
> 1)      Humongus allocation request for 72 mb failed, from the logs we
> can also see we have free space of  around 3 GB. Does this means , our
> application is encountering high  amount of fragmentation ?.
>
> It is possible. What it means is g1 can not find 36 consecutive regions
> for that 72 mb object.
>
> I agree the ReservePercent=40 is too high, but that should not prevent
> allocating to the old gen. G1 tries to honor ReservePercent.
>
So just to clarify - is the space (i.e. regions) reserved by
G1ReservePercent allocatable to humongous object allocations? All
docs/webpages I found talk about this space being for holding survivors
(i.e. evac failure/to-space exhaustion mitigation).  It sounds like you're
saying these reserved regions should also be used to satisfy HO allocs?

Thanks
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