confluence garbage collection and Optimization

Paul DeSousa1

Hi Conf Admins,

I am preparing our site for the new 5.7.3 upgrade and began investigating my setenv.sh CAT opts that are passed and noticed that I have a lot for GC:

CATALINA_OPTS="$CATALINA_OPTS -Xloggc:$LOGBASEABS/logs/gc-`date +%F_%H-%M-%S`.log -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2M"
CATALINA_OPTS="$CATALINA_OPTS -XX:-PrintGCDetails -XX:+PrintGCTimeStamps -XX:-PrintTenuringDistribution"

If I was debugging GC the above would make sense, but since we are stable, should I remove all the GC logging information?  Would this help performance at all?    What would the side effects be if I remove the above two lines or just the last one at least?

Also Does anyone know about this parm: 

-XX:+OptimizeStringConcat

Does that help with latency?  Should I add that?

Thanks in advance,

Robert

 

Rodrigo Girardi Adami

Hi Robert,

I have not tried to remove those parameters yet, but they are just to log the GC activity of the JVM. This is particularly helpful when you have memory/performance issues. You are not going to have a huge increase of performance if you remove those parameters or comment them.

My recommendation is to keep them as it is, unless you really want to fine tune and gain a very small improvement.

As for the OptimizeStringConcat parameter, according to here it seems that:

It recognizes pattern like new StringBuilder().append(...).toString()
with ... being a String, a char or an int (it doesn't seem to recognize 
if it's an Object)
and tries to create the corresponding String once.

I hope this helps!

Cheers,

Rodrigo