Java 8 adding -XX:MaxNewSize to parameters

[Thomas Schatzl]

Hi Shawn,

On Fri, 2018-11-02 at 15:23 -0600, Shawn Heisey wrote:
> I have a Solr install with the following info on the process list:
> 
> solr      4426     1 15 Sep27 ?        5-17:59:51 java -server
> -Xms7943m 
> -Xmx7943m -XX:+UseG1GC -XX:+PerfDisableSharedMem 
> -XX:+ParallelRefProcEnabled -XX:G1HeapRegionSize=8m 
> -XX:MaxGCPauseMillis=250 -XX:InitiatingHeapOccupancyPercent=75 
> -XX:+UseLargePages -XX:+AggressiveOpts -verbose:gc
> -XX:+PrintHeapAtGC 
> -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintGCTimeStamps 
> -XX:+PrintTenuringDistribution -XX:+PrintGCApplicationStoppedTime 
> -Xloggc:/data/solr-home/logs/solr_gc.log -XX:+UseGCLogFileRotation 
> -XX:NumberOfGCLogFiles=9 -XX:GCLogFileSize=20M 
> 
> [...]
> 
> Process started Sep27, with G1 tuning, but no parameters setting 
> specific generation sizes.
> 
> Here's the info at the top of a GC log written by that process:
> 
> 2018-10-29 05:47:53 GC log file created /data/solr-
> home/logs/solr_gc.log.6
> Java HotSpot(TM) 64-Bit Server VM (25.162-b12) for linux-amd64 JRE 
> (1.8.0_162-b12), built on Dec 19 2017 21:15:48 by "java_re" with gcc 
> 4.3.0 20080428 (Red Hat 4.3.0-8)
> Memory: 4k page, physical 16268024k(163252k free), swap 
> 2098172k(2056676k free)
> CommandLine flags: -XX:+AggressiveOpts -XX:CICompilerCount=3 
> -XX:ConcGCThreads=1 -XX:G1HeapRegionSize=8388608 
> -XX:GCLogFileSize=20971520 -XX:InitialHeapSize=8329887744 
> -XX:InitiatingHeapOccupancyPercent=75 -XX:+ManagementServer 
> -XX:MarkStackSize=4194304 -XX:MaxGCPauseMillis=250 
> -XX:MaxHeapSize=8329887744 -XX:MaxNewSize=4991221760 
> -XX:MinHeapDeltaBytes=8388608 -XX:NumberOfGCLogFiles=9 
> -XX:OnOutOfMemoryError=/data/solr/bin/oom_solr.sh 8983 
> /data/solr-home/logs -XX:+ParallelRefProcEnabled 
> -XX:+PerfDisableSharedMem -XX:+PrintGC 
> -XX:+PrintGCApplicationStoppedTime -XX:+PrintGCDateStamps 
> -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintHeapAtGC 
> -XX:+PrintTenuringDistribution -XX:ThreadStackSize=256 
> -XX:+UseCompressedClassPointers -XX:+UseCompressedOops 
> -XX:+UseFastUnorderedTimeStamps -XX:+UseG1GC
> -XX:+UseGCLogFileRotation 
> -XX:+UseLargePages
> 
> As you can see, the gc log says that -XX:MaxNewSize is among the 
> parameters.  The problem came to my attention when I put the gc log
> into the gceasy.io website and it said "don't set your generation
> sizes explicitly, G1 works better when they aren't explicit."  Which
> I thought was weird, because I didn't know of anywhere that the sizes
> were being set.  I don't WANT to set the generation sizes explicitly.
> 
> I have confirmed by cross-referencing pids, checking which pid has
> the logfile open, and watching for new data written to the same log
> that it is indeed the same process, so I know the commandline
> arguments from the ps listing are from the right process.
> 
> Here's the version info for the java version that's running:
> 
> [solr at RWVM-SolrDev03 logs]$ java -version
> java version "1.8.0_162"
> Java(TM) SE Runtime Environment (build 1.8.0_162-b12)
> Java HotSpot(TM) 64-Bit Server VM (build 25.162-b12, mixed mode)
> 
> I cannot reproduce the behavior manually on a Windows 10 machine,  
> either with the same version that's on the Linux machine or using 
> 8u_191.  The machine where I see this happening is running CentOS
> 7.  
> Hopefully I will be in a position to restart the service on the
> machine in the near future so I can check whether the issue is
> persistent.
> 
> I will attempt to reproduce on another Linux machine.  Does this
> seem like a bug?

I remember that is a (known) bug in printing command line flags. This
may also occur the other way around, i.e. flags specified on the
command line are not printed.

This has no impact on flags actually used.

I spent some time coming up with an existing bug number for that, but
failed.

Looking at the code that prints these flags, it actually prints any
command line flags modified so far (including e.g. ergonomics), which
depending on the time the method is called, adds or removes some flags
in the output.

Thanks,
  Thomas