Handle PrintGCApplicationStoppedTime flag in java

My application is using gc flag "PrintGCApplicationStoppedTime" but when am running it with Java 9 it is failing with following error:

Unrecognized VM option 'PrintGCApplicationStoppedTime'
Error: Could not create the Java Virtual Machine.
Error: A fatal exception has occurred. Program will exit.

This post indicate that option is deprecated but is there any alternative for the information printed by his flag or this information is no longer available?

回答1:

Few things to know there:

First, well the answer here by @apangin sums up quite well that the PrintGCApplicationStoppedTime prints the time spent inside safepoints.

In order to dump more details onto the safe points of your application you shall better make use of:

-XX:+PrintSafepointStatistics -XX:PrintSafepointStatisticsCount=1

Second, Java 9 plans to implement Unified GC logging under JEP#271 which at the same time would make use of the Unified JVM Logging under JEP#158

Going forward with which -Xlog would be used as a new command-line option to control logging from all components of the JVM. The logging would thereby follow the syntax(quoted):

-Xlog[:option]
    option         :=  [<what>][:[<output>][:[<decorators>][:<output-options>]]]
                       'help'
                       'disable'
    what           :=  <selector>[,...]
    selector       :=  <tag-set>[*][=<level>]
    tag-set        :=  <tag>[+...]
                       'all'
    tag            :=  name of tag
    level          :=  trace
                       debug
                       info
                       warning
                       error
    output         :=  'stderr'
                       'stdout'
                       [file=]<filename>
    decorators     :=  <decorator>[,...]
                       'none'
    decorator      :=  time
                       uptime
                       timemillis
                       uptimemillis
                       timenanos
                       uptimenanos
                       pid
                       tid
                       level
                       tags
    output-options :=  <output_option>[,...]
    output-option  :=  filecount=<file count>
                       filesize=<file size in kb>
                       parameter=value

Where picking up few varied examples to learn from would be:

```
-Xlog:gc=trace:file=gctrace.txt:uptimemillis,pids:filecount=5,filesize=1024
```
- log messages tagged with 'gc' tag using 'trace' level to a rotating fileset with 5 files with size 1MB with base name 'gctrace.txt' and use decorations 'uptimemillis' and 'pid'
- default output of all messages at level 'warning' to 'stderr' will still be in effect
```
-Xlog:gc+rt+compiler*=debug,meta*=warning,svc*=off
```
- log messages tagged with at least 'gc' and 'rt' and 'compiler' tag using 'trace' level to 'stdout' but only log messages tagged with 'meta' with level 'warning' or 'error' and turn off all messages tagged with 'svc'
- default output of all messages at level 'warning' to 'stderr' will still be in effect

回答2:

See also JDK 9 release notes where the implications of unified logging (-Xlog) are detailed: http://jdk.java.net/9/release-notes#JDK-8145092 You'll see that PrintGCApplicationStoppedTime and several options have been removed.