ZGC Unable to reclaim memory for long time

Per Liden per.liden at oracle.com
Thu Nov 7 07:25:10 UTC 2019

On 11/7/19 2:28 AM, Sundara Mohan M wrote:
> Unfortunately i don't have that stats. I was running application with 
> this option for gc 
> log -Xlog:gc,gc+init,gc+start,gc+phases,gc+heap,gc+cpu,gc+reloc,gc+ref,gc+marking,gc+metaspace=info.
> Will see if i can get that issue reproducible and get that data for you.

Ok, thanks. I'd recommend using -Xlog:gc*, that way you catch pretty 
much all you need to tell what's going on, without being super verbose.


> Thanks
> Sundar
> On Wed, Nov 6, 2019 at 3:08 PM Per Liden <per.liden at oracle.com 
> <mailto:per.liden at oracle.com>> wrote:
>     On 11/6/19 10:04 PM, Sundara Mohan M wrote:
>     [...]
>      > But on the other hand with ZGC my throughput increased from
>      > *(ParallelGC)97%* to*(ZGC)99.7% *and my STW pauses have never
>     crossed 20ms.
>     Could you please paste the last printout of the "Garbage Collection
>     Statistics" table? If you have pauses close to 20ms, it would be
>     interesting to see where that time is spent. I would assume it's
>     accounted to "Subphase: Pause Roots Threads", but seeing the whole
>     table
>     would tell the me more.
>     thanks,
>     Per

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