What versions of java are slow for gc logging?

Question

I've been told by my company's support team that some versions of java have a significant performance impact when we turn on -verbose:gc. However I can't figure out if this is the case or not.

Was this logging slow(ish) at some point, and when did it stop?

The reason I ask is that there's some hesitation about applying this to a production environment to investigate potential memory leaks (and whether we can stop doing periodic restarts of the system...).

Specifically I'm talking about Java 1.4.2 which I think introduced the argument, and what service pack it applies up to.

Answer 1

I know you asked about the impact of verbose:gc (Amir is correct), but based on the comments I see you are investigating a memory leak.

Is it possible for you to get a histogram of your environment? verbose GC will only show you that there is a memory leak, not where the memory is sitting.

you mention java 1.4.2, is that your current version? If you are using 1.5 or higher you can use

jmap -histo <pid> > file.txt

This will give you a breakdown of all the objects in memory. You will freeze your JVM for a time dependent on the amount of memory in the system. (2GB can freeze for a minute or so on even good hardware) test this on a development system first. I know you don't want to impact your production environment but this is a necessary evil to find the source of the problem. Do a capture right before the periodic restart to lesson your impact.