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Home > Archive > WebSphere Application Server > August 2005 > Generational GC - Young Generation Allocation | IBM WAS 5.1.0.3 && JDK 1.4.1
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Generational GC - Young Generation Allocation | IBM WAS 5.1.0.3 && JDK 1.4.1
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| Hi
As part of tuning the performance of our JVMs on our project we wanted to define the initial JVM heap settings and restructure the heap to allocate specific amount of memory into the young (eden) generation based on the application requirement. However wh
ile trying to configure this using the –XX:NewSize=128m –XX:MaxNewSize=128m we ran into issues during the JVM start up as it gave the following error:
“[ Unrecognized option: -XX:NewSize=128m ]. [ JVMCI123: Unable to parse 1.2 format”
Doing some more research on this exception on the net, it seems that the –XX JVM arguments catered towards structuring the heap and enabling Generational GCs are not supported for the JDK version used on our application. Here are the details for JDK and
App Server used:
App Server – IBM WebSphere 5.1.0.3
JDK – IBM 1.4.1
Type – Classic (Not Hot Spot)
M/C – IBM PServer P570
AIX 5.2
Here are some of the relevant links that we found on the net that talk about Generational GCs and –XX arguments NOT being supported in this IBM JRE version:
http://www-128.ibm.com/developerwor...-Javaperf5.html
http://www-106.ibm.com/developerwor...essage=13695933
Considering the impact that a poor heap allocation and structuring can have on our PRODUCTION environment we would really like to make the maximum use of some of the new GC algorithms or at the least divide the heap into different generations to avoid a f
ull GC in every GC cycle.
Have any of you have faced a similar issue while using the same JDK and IBM Web Sphere combination. Is there a separate way of specifying or simulating a Generational GC in JDK 1.4.1.
We also read somewhere that with IBM JDK/JRE 1.4.2, support for Hotspot and generation garbage collection is available? Is that true? Does that confirm, that this is available ONLY starting 1.4.2 and will therefore not work with our current Websphere/JRE
version?
Any inputs on this would be most appreciated.
~Mayur
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| Bibhas Bhattacharya 2005-08-16, 6:01 pm |
| Generational GC applies to Sun JDK only which is used by WebSphere in
Solaris and HPUX only. In other OS, IBM JDK is used. IBM JDK will choke on
the command line options you mentioned.
--
Bibhas Bhattacharya
WebSphere, WebLogic Training and Consulting
www.webagesolutions.com
<axerxes@sapient.com> wrote in message
news:506968346.1113927104699.JavaMail.wassrvr@ltsgwas007.sby.ibm.com...
> Hi
>
> As part of tuning the performance of our JVMs on our project we wanted to
define the initial JVM heap settings and restructure the heap to allocate
specific amount of memory into the young (eden) generation based on the
application requirement. However while trying to configure this using the
?"XX:NewSize=128m ?"XX:MaxNewSize=128m we ran into issues during the JVM
start up as it gave the following error:
>
> ?o[ Unrecognized option: -XX:NewSize=128m ]. [ JVMCI123: Unable to parse
1.2 format?
>
> Doing some more research on this exception on the net, it seems that the
?"XX JVM arguments catered towards structuring the heap and enabling
Generational GCs are not supported for the JDK version used on our
application. Here are the details for JDK and App Server used:
>
> App Server ?" IBM WebSphere 5.1.0.3
> JDK ?" IBM 1.4.1
> Type ?" Classic (Not Hot Spot)
> M/C ?" IBM PServer P570
> AIX 5.2
>
> Here are some of the relevant links that we found on the net that talk
about Generational GCs and ?"XX arguments NOT being supported in this IBM
JRE version:
>
> http://www-128.ibm.com/developerwor...-Javaperf5.html
>
>
http://www-106.ibm.com/developerwor...p?thread=73606&
forum=367&cat=10&message=13695933
>
> Considering the impact that a poor heap allocation and structuring can
have on our PRODUCTION environment we would really like to make the maximum
use of some of the new GC algorithms or at the least divide the heap into
different generations to avoid a full GC in every GC cycle.
>
> Have any of you have faced a similar issue while using the same JDK and
IBM Web Sphere combination. Is there a separate way of specifying or
simulating a Generational GC in JDK 1.4.1.
>
> We also read somewhere that with IBM JDK/JRE 1.4.2, support for Hotspot
and generation garbage collection is available? Is that true? Does that
confirm, that this is available ONLY starting 1.4.2 and will therefore not
work with our current Websphere/JRE version?
>
>
>
>
> Any inputs on this would be most appreciated.
>
>
>
> ~Mayur
>
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