XX:MaxPermSize=128m for Tomcat 8 / Java 7, why?

[Walter Forbes Hoehn (wassa)]

I think it’s likely that is just stale advice that has been carried forward.  Regardless, the setting has been eliminated completely in JRE8.

-WFH


> On Nov 20, 2015, at 8:38 AM, Etienne Dysli-Metref <etienne.dysli-metref at switch.ch> wrote:
> 
> The wiki page
> https://wiki.shibboleth.net/confluence/display/IDP30/ApacheTomcat8
> recommends putting -XX:MaxPermSize=128m in CATALINA_OPTS to set the
> PermGen space size, but unfortunately without saying why this is
> necessary. Does anyone know the explanation?
> 
> It turns out this actually makes the PermGen space *smaller* depending
> on the amount of RAM your machine has. I've tried with 1, 2 and 8GB and
> my JVM would always choose 166MB for PermGen. I don't see any reason to
> reduce PermGen, especially with Tomcat having a tendency to quickly fill
> it up when redeploying a webapp several times.
> 
> For example:
> 
> $ java -XX:MaxPermSize=128m -XX:+PrintFlagsFinal -version | grep PermSize
>  uintx AdaptivePermSizeWeight   = 20              {product}
>  uintx MaxPermSize             := 134217728       {pd product}
>  uintx PermSize                 = 21757952        {pd product}
> java version "1.7.0_91"
> OpenJDK Runtime Environment (rhel-2.6.2.1.el7_1-x86_64 u91-b00)
> OpenJDK 64-Bit Server VM (build 24.91-b01, mixed mode)
> 
> $ java -XX:+PrintFlagsFinal -version | grep PermSize
>  uintx AdaptivePermSizeWeight   = 20              {product}
>  uintx MaxPermSize              = 174063616       {pd product}
>  uintx PermSize                 = 21757952        {pd product}
> java version "1.7.0_91"
> OpenJDK Runtime Environment (rhel-2.6.2.1.el7_1-x86_64 u91-b00)
> OpenJDK 64-Bit Server VM (build 24.91-b01, mixed mode)
> 
> $ free -h
>     total     used     free   shared  buff/cache   available
> Mem:  993M     609M      81M      14M        301M        231M
> Swap: 1.5G       0B     1.5G
> 
>  Etienne
> 
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