Hi there,
see inline for my take to answering your questions. If someone has
more info please share and/or correct.
On Sun, Aug 21, 2011 at 10:39 AM, mike_t t.pr...@gmx.net wrote:
I installed neo4j as a service on linux. Then I configured in the
neo4j-community-1.4.1/conf/neo4j-wrapper.conf file following init and max
memory:
# Initial Java Heap Size (in MB)
wrapper.java.initmemory=512
# Maximum Java Heap Size (in MB)
wrapper.java.maxmemory=768
The top output shows following:
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
17408 neo4j 18 0 1188m 155m 11m S 0 5.1 2:12.76 java
Should neo4j not reserverd 512m memory? What did I wrong?
Asking for any amount of memory does not mean that the memory pages
are actually allocated - they are reserved. The JVM marks a range of
addresses as reserved and the OS obliges, but through the way virtual
memory works, the RAM is not actually used. This means that the JVM
thinks that it has 512M but the OS knows better. The upside of not
needing to do re-sizing calculations on heap growth is still there -
when the JVM decides to write to a reserved page that is not still
allocated, a page fault will be raised, the kernel will intervene etc,
as per usual.
How can I discover If neo4j is running in java server mode? Result of java
-version is:
OpenJDK 64-Bit Server VM (build 19.0-b09, mixed mode).
Interesting question. It seems there is no vendor independent way -
the client vs server thing is vendor dependent to begin with. The
closest thing that seems to work is parsing the VM name string,
reachable via
System.getProperty( java.vm.name )
which on my machine returns
Java HotSpot(TM) 64-Bit Server VM
with java -version printing
java version 1.6.0_24
Java(TM) SE Runtime Environment (build 1.6.0_24-b07)
Java HotSpot(TM) 64-Bit Server VM (build 19.1-b02, mixed mode)
The same is reported of course via jconsole. Interestingly, i could
not start a client JVM. The JRE's help text talks about a -server
option only and that the default is server. No -client, although the
JVM starts with it in the command line. I guess this has to do with
all my machines being 64-bit multicore.
Hope the above helped.
cheers,
CG
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