java process memory usage is higher than Xmx

[Thomas Schatzl]

Hi,

On Mon, 2014-01-06 at 12:03 -0800, yao wrote:
> Hi All,
> 
> I have a java process (HBase region server process ) running under
> Java 7 (1.7.0_40-b43) with G1 enabled. Both Xms and Xmx are the same.
> After running process for a few hours, I see the actual memory used by
> the process is about 10 percent higher than given Xmx. Has anyone
> experienced the similar when use Java 7 or G1 ? Is there useful tools
> to diagnose the cause ?
> 
> 
> I've tried jmap but the output doesn't say anything about high memory
> usage. FYI, the java process use a large heap (90GB), but the actual
> memory usage ($ top) is about 99GB.
> 
Possibly remembered set size.

Can you enable -XX:+UnlockDiagnosticVMOptions and -XX:
+G1SummarizeRSetStats?

The line

  Total heap region rem set sizes = 5256086K.  Max = 8640K.

gives you a good idea about remembered set size memory usage.

I copied above line from one of your responses to the "G1 GC clean up
time is too long" thread, and it seems the remembered set takes ~5GB
there.

Hth,
Thomas