> (1) I cannot stress this one enough: Run with -XX:+PrintGC > -XX:+PrintGCDetails -XX:+PrintGCTimeStamps and collect the output.
Actually, I wonder if it's worth someone getting this enabled by default, with the obvious problems associated with getting the log output placed appropriately and rotated. But it really seems to me like almost every single case of people having problems on the ML:s would be helped by having instant access to the GC log to rule things out very quickly and expediently. I'm not aware of a good simple way to do so though, since the JVM emits it on stdout (not even stderr) by default, or else to a fixed file and supports no rotation. Making the file a fifo is possible, but then one has to have someone reading that file and then that thing must be monitored, and you introduce the possibility of the log reader causing JVM hiccups, etc.... does anyone have a good practice for running production code with GC logging in a way that doesn't interfer with the normal user who's not actively using it/caring about it? A related potential mode of backfire is that it might cause blocking writes to stdout on systems bottlenecking on disk I/O. Maybe it's just not realistic. -- / Peter Schuller
