Feedback requested: HotSpot GC logging improvements

Peter B. Kessler Peter.B.Kessler at Oracle.COM
Thu May 6 22:00:43 UTC 2010

+1 on using date stamps in the file names if you have to split a GC log into several files.

If you use the same format as is used for the -XX:+PrintGCDateStamps, ISO 8601, then lexicographic order, e.g. from file listings, should also be in time sequence order, which would be convenient.  (Then, if only we could get PID's to be monotonically increasing. :-)  That might imply that you want PID's after (less significant than) time stamps in the split file names, so you still get them in time sequence order.  If you want just the logs from PID 1234, you can use "ls *.1234.*" to get just those, in time sequence order.

Do you want an option to start a new log file in a sequence after some period of time?  E.g., once a day?  That might make it easier to line up events across long-running JVM's that are collecting (and therefore generating logs) at different rates.

+1 on including the command line arguments (or maybe the settings those provoke inside the VM) in the log file.  For settings that change over time, e.g., because of ergonomics, it would be good to have a way to see those, too.  Maybe "a new log file format" allows that to happen.

			... peter

Matt Khan wrote:
> Evening
> we currently manage the log overwriting issue by mv'ing the last gc.log 
> to gc.log.<timestamp when the new jvm one starts>, if you're going to 
> roll the logs then I would prefer a meaningful suffix rather than just a 
> counter.
> I second the idea that datestamps should be the default.
> I think a unified, easily parseable but still readable output would be 
> great though wouldn't you still need a verbose output that is specific 
> to each collector in order to provide a "debug" level of detail?
> Cheers
> Matt
> Matt Khan
> --------------------------------------------------
> GFFX Auto Trading
> Deutsche Bank, London
hotspot-gc-use mailing list
hotspot-gc-use at

More information about the hotspot-gc-dev mailing list