Troubleshooting a ~40-second minor collection

[Aaron Daubman]

Hi Bengt,

Thanks for the pointers - it feels like there may be some hints here as to
what to look at next!


> This GC has has this user/real time info:
>
> [Times: user=0.17 sys=0.00, real=3.45 secs]
>
> That means that during 3.45 seconds all of the VM threads only got
> scheduled to actually run on the CPUs for 0.17 seconds. So, it seems like
> the OS has scheduled the VM threads out for most of that period. The reason
> for that is most likely that the system is running too many other
> applications at the same time.
>


When I see these longer pause times its during the high-rate (~100M/s) file
copy and un-tar onto this system. This uses at most 2 out of the 32 cores
on this server. So I am still very confused as to what would prevent the VM
threads from being scheduled... anybody have any ideas?  (The server runs
at a load average of ~2 on a 32 core system)

Would high context switching or some type of I/O wait have any impact on
long real vs. user GC time here? I'm having a hard time imagining how that
would happen... especially since all of the memory should be active now...

Thanks again,
      Aaron
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