Odd G1GC behavior on 8u91

[Jenny Zhang]

More comments about the questions

Thanks
Jenny

On 8/24/2016 11:43 AM, Vitaly Davidovich wrote:
> Right before the Full GC, ergonomics report a failure to expand the 
> heap due to an allocation request of 32 bytes.  Is this implying that 
> a mutator tried to allocate 32 bytes but couldn't? How do I reconcile 
> that with Eden+Survivor occupancy reported right above that?
Yes, it means the mutator tries to allocate 32byte but can not get it. 
Heap won't expand as it already reaches max heap.

Do you see any humongous objects allocatoin?
>
> Young gen is sized to 30GB, total heap is 96GB.  Allocation rate of 
> the application is roughly 1GB/s.  Am I correct in assuming that 
> allocation is outpacing concurrent marking, based on the above? What 
> tunable(s) would you advise to tweak to get G1 to keep up with the 
> allocation rate? I'm ok taking some throughput hit to mitigate 90s+ 
> pauses.
>
The entire log might give a better picture. Especially if the marking 
cycle is triggered, how well the mixed gc cleans up the heap.