G1GC, Java8u40ea, Metaspace questions

[Jon Masamitsu]

On 02/26/2015 01:19 AM, Wolfgang Pedot wrote:
> Jon,
>
> Am 26.02.2015 01:02, schrieb Jon Masamitsu:
>> Wolfgang,
>>
>> Can you run you test program with UseParallelGC and see if you
>> see the same growth in the Metaspace?
>>
>
> test is now running for a good 30min and it does not look like there 
> is growth.
> The configuration is the same as before, I just changed +UseG1GC to 
> -UseG1GC and added +UseParallelGC. This collector is more successful 
> in getting rid of classes right away so Metaspace usage after GC stays 
> around ~110MB.
> MetaspaceSize is configured to 300MB (Max is 2000MB) and the maximum 
> values for commited Metaspace in the gclog are 307200K, I have 
> attached a screenshot of jconsole showing Metaspace usage.
> Since usage stays lower than with G1 I am not sure if this is a "fair" 
> test regarding HWM calculation.

Thanks for running the tests.  The difference could be the result of
UseParallelGC doing a STW full collection when the HWM is reached
and G1 starting a concurrent collection when the HWM is reached.
I could accept the HWM with G1 being higher but having it grow
is a bug.

Jon

>
> Wolfgang
>