-XX:+TraceClassUnloading enabled w/ -Xloggc ?

[Bengt Rutisson]

Charlie,

I don't see any code that enables TraceClassUnloading when -Xloggc is 
used. Are you sure that this happens?

When I run it also doesn't look like it gets enabled.

 >java -Xloggc:log.txt -XX:+PrintFlagsFinal -version | grep 
TraceClassUnloading
      bool TraceClassUnloading                       = false           
{product rw}
java version "1.8.0-ea"
Java(TM) SE Runtime Environment (build 1.8.0-ea-b60)
Java HotSpot(TM) Client VM (build 25.0-b04, mixed mode)

We do enable PrintGC and PrintGCDetails when -Xloggc is enabled:

     if (match_option(option, "-Xloggc:", &tail)) {
       // Redirect GC output to the file. -Xloggc:<filename>
       // ostream_init_log(), when called will use this filename
       // to initialize a fileStream.
       _gc_log_filename = strdup(tail);
       FLAG_SET_CMDLINE(bool, PrintGC, true);
       FLAG_SET_CMDLINE(bool, PrintGCTimeStamps, true);

     // JNI hooks
     }

Bengt


On 2012-10-29 16:06, Charlie Hunt wrote:
> We stumbled across this last week ... and now curious.
>
> With -Xloggc, -XX:+TraceClassUnloading is also enabled.  But, with other GC related command line options such as; -XX:+PrintGCDetails, -XX:+PrintGC, -XX:+PrintHeapAtGC, etc. -XX:-TraceClassUnloading remains disabled by default.
>
> Anyone know the history that led to the decision to only enable +TraceClassUnloading with -Xloggc, and not with say +PrintGCDetails?
>
> thanks,
>
> charlie ...