ParallelOldGC vs ParallelGC

mbien at fh-landshut.de mbien at fh-landshut.de
Wed Dec 17 00:43:38 PST 2008


thank you,
it worked indeed, it seems like jconsole doesn't detect the gc correctly.

-XX:+PrintCommandLineFlags is now default for all my projects ;)

regards,
michael

Zitat von Jon Masamitsu <Jon.Masamitsu at Sun.COM>:

> Run the command
>
> java -server -XX:+UseParallelGC -XX:+PrintCommandLineFlags -version
>
> You should see something like
>
> java -server -XX:+UseParallelGC -XX:+PrintCommandLineFlags -version
> -XX:MaxHeapSize=536870912 -XX:+PrintCommandLineFlags -XX:+UseParallelGC
> java version "1.5.0_16"
> Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_16-b02)
> Java HotSpot(TM) Server VM (build 1.5.0_16-b02, mixed mode)
>
> Note the -XX:+UseParallelGC that is printed which indicates that the
> parallel young generation collector is being used.
>
> Then run
>
> java -server -XX:+UseParallelOldGC -XX:+PrintCommandLineFlags -version
>
> You should see
>
> java -server -XX:+UseParallelOldGC -XX:+PrintCommandLineFlags -version
> -XX:MaxHeapSize=536870912 -XX:+PrintCommandLineFlags -XX:+UseParallelGC
> -XX:+UseParallelOldGC
> java version "1.5.0_16"
> Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_16-b02)
> Java HotSpot(TM) Server VM (build 1.5.0_16-b02, mixed mode)
>
> Note that both -XX:+UseParallelGC and -XX:+UseParallelOldGC appear so
> you should be running the parallel young generation collector and the
> parallel old generation collector.
>
> If you see something different, what platform are you running on?
> Can you send a snippet of the GC log?
>
> On 12/16/08 01:28, mbien at fh-landshut.de wrote:
>> Hello everyone,
>>
>> is there still a difference between both flags? In all my tests on   
>> jdk 5 the VM was initialized each time with identical gc setups.
>>
>> flags:
>> -server -XX:+UseParallelOldGC -verbose:gc -XX:+PrintGCDetails    
>> -XX:+PrintGCTimeStamps
>>
>> -server -XX:+UseParalleldGC -verbose:gc -XX:+PrintGCDetails    
>> -XX:+PrintGCTimeStamps
>>
>> jconsol reported in both cases PS MarkSweep and PS Scavange    
>> collectors. (what does PS mean?)
>>
>> i always thought that ParallelGC would result in
>> parallel young + serial old
>> and ParrallelOldGC in
>> parrallel young + parralel old gcs
>>
>> best regards,
>>
>> michael
>>
>> _______________________________________________
>> hotspot-gc-use mailing list
>> hotspot-gc-use at openjdk.java.net
>> http://mail.openjdk.java.net/mailman/listinfo/hotspot-gc-use



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