[kepler-dev] Question regarding startup parameters

[Daniel Crawl]

Hi Michal,

Before Kepler 2.4, the minimum memory value in memory.xml
was used with "-Xss". This was changed to "-Xms" in 2.4.
Do you want to set stack size ("-Xss") too?

   --dan

On 4/23/14 3:53 AM, Michal Owsiak wrote:
> Hello Kepler team,
>
> I have question related to startup parameters of Kepler sub process (JVM
> started by Run.java).
>
> I am starting Kepler and what I can see is that it starts two Java
> processes.
>
> 1. used for initialization
> 2. used for actual Kepler application
>
> Inside build-area/build-area/src/org/kepler/build/Run.java
>
> there is following fragment of code (Kepler 2.4):
>
> java.createJvmarg().setLine("-Xmx" + jvmMaxMemory);
> java.createJvmarg().setLine("-Xms" + jvmMinMemory);
> java.createJvmarg().setLine("-Xss" + jvmMinMemory);
>
> relese 2.3 has slightly different fragment:
>
> java.createJvmarg().setLine("-Xmx" + jvmMaxMemory);
> java.createJvmarg().setLine("-Xss" + jvmMinMemory);
>
> The issue here is, that -Xss is defined per thread.
>
>  From Oracle's JRockit explanation:
>
> "The -Xss flag specifies how much stack each thread should be allocated.
> Thread stacks are the memory areas allocated for each Java thread for
> their internal use. This is where the thread stores its execution state.
> It normally makes little sense to increase this size, unless there is
> plenty of recursion or a large amount of stack local information. For
> example, -Xss:256k will set the thread stack size to 256 KB."
>
> It means, that each time new thread is started we will try to allocate
> as much memory as declared by jvmMinMemor, that is read from:
>
> <entry key="min">1000m</entry>
>
> inside
>
> build-area/settings/memory.xml
>
> The point here is that current code doesn't allow to allocate certain
> amount of memory while JVM is started. If I will declare that I want 2G
> at minimum, it means that each thread will gain 2G as well for it's
> internal stack.
>
> Is that correct?
>
> I think there should be another setting inside memory.xml, e.g.
>
> <entry key="stack">128k</entry>
>
> Cheers
>
> Michal
>