ZGC cpu metrics in logs

Per Liden per.liden at oracle.com
Thu Oct 24 07:57:10 UTC 2019


On 10/24/19 2:49 AM, Sundara Mohan M wrote:
> Hi,
>      Wondering why zgc doesn't print cpu metrics like below
> [2019-10-23T17:42:48.539+0800][0.959s][info][gc,cpu      ] GC(118)
> User=0.00s Sys=0.00s Real=0.00s
> For any other garbage collectors it is printed.
> Is this avoid because ZGC stop the world pause is always in milliseconds?
> Just curious why this was not printed for ZGC alone.

Right, printing that exact line wouldn't be that useful, as ZGC pauses 
wouldn't normally register on that scale.

However, printing more detailed timing information could certainly be 
useful. We've especially been interested in real-time vs. cpu-time, as 
that can often explain strange outliers, expose over provisioning, etc.


> Thanks
> Sundar

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