Max possible heap size for Concurrent Mark Sweep collector.

[Srinivas Ramakrishna]

It can't be a fundamental limitation, from what I can tell and what I recall.  The failure is in allocating the marking bit map for the old gen. Could it be that you don't have enough swap configured to back the virtual address space required for this setup? You could strace the launch and see why the mmap request might be failing.

-- Ramki

ysr1729

> On Sep 10, 2014, at 14:53, Alexey Ragozin <alexey.ragozin at gmail.com> wrote:
> 
> Hi,
> 
> Sometimes ago we have tried to setup 200GiB heap per JVM using CMS GC.
> Oracle HotSpot JVM have failed to start with following error
> 
> Java HotSpot(TM) 64-Bit Server VM warning: CMS bit map allocation failure 
> Java HotSpot(TM) 64-Bit Server VM warning: Failed to allocate CMS Bit Map 
> Error occurred during initialization of VM 
> Could not create CMS collector 
> Error: Could not create the Java Virtual Machine. 
> Error: A fatal exception has occurred. Program will exit.
> 
> JVM command line
> 
> /usr/java/jdk1.7.0_60/bin/java -d64 -verbose:gc -XX:+UseConcMarkSweepGC -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -Xmn512m -XX:MaxTenuringThreshold=1 -Xms200G -Xmx200G -XX:+UseCMSInitiatingOccupancyOnly -XX:CMSInitiatingOccupancyFraction=90 -Duse-cached-field-op=false  -XX:MaxPermSize=1024m -Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=13521 -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false -XX:-UsePopCountInstruction  APPLICATION_MAIN_CLASS ...
> 
> We have reduced -Xmx to 180GiB and currently that is our configuration.
> Provided amount of memory on our standard hardware setup, using JVM with 400 GiB would be desirable.
> 
> My question is
> 
> Is that 200GiB fundamental limitation of CMS algorithm or it is something what could be remedied?
> 
> Any relevant pointers to open JDK code base would be appreciated.
> 
> Regards,
> Alexey
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