RFR: 8270801: Print VM arguments with java -Xlog:arguments

[Thomas Stuefe]

On Thu, 15 Jul 2021 22:48:51 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> It's useful to print VM arguments to the log file, especially when you are logging several JVM invocations:
> 
> 
> $ java -cp foo -Xlog:gc:file=a.log -Xcomp com.Foo
> $ java -cp foo -Xlog:gc:file=b.log -Xint com.Foo
> 
> 
> After a while, you may forget which process created a.log and which created b.log. Adding vm arguments into the log file will help distinguishing them:
> 
> 
> $ java -cp foo -Xlog:gc,arguments:file=a.log -Xcomp com.Foo
> $ java -cp foo -Xlog:gc,arguments:file=b.log -Xint com.Foo
> 
> $ grep jvm_args a.log b.log
> a.log:[0.015s][info][arguments] jvm_args: -Xlog:gc,arguments:file=a.log -Xint
> b.log:[0.001s][info][arguments] jvm_args: -Xlog:gc,arguments:file=b.log -Xcomp
> 
> 
> Here's an example of what the log looks like:
> 
> 
> $ java -Xlog:arguments -Xshare:on -cp ~/tmp -Dxx=yy -esa HelloWorld 1 2 3
> [0.001s][info][arguments] VM Arguments:
> [0.001s][info][arguments] jvm_args: -Xlog:arguments -Xshare:on -Dxx=yy -esa
> [0.001s][info][arguments] java_command: HelloWorld 1 2 3
> [0.001s][info][arguments] java_class_path (initial): /home/user/tmp
> [0.001s][info][arguments] Launcher Type: SUN_STANDARD
> Hello World

Side note, I wish we had a similar option to print the pid (and not much else). In our proprietary port, we have a -XshowPid, which I use surprisingly often, even in scripts.

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PR: https://git.openjdk.java.net/jdk/pull/4801