Hi John, Thanks for the feedback. The milliseconds/ticks issue indeed seems to be bug 7087969. Will the upcoming 7u14 contain hs24, and the fix?
Regarding the "No GC" cause, I think http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8006954 might be the underlying issue. If I understand correctly, it's now fixed for hs24 as well, and will hopefully be part of 7u14. I'll post any follow-up questions regarding the GC Notification API to the serviceability-dev mailing list. Kind regards, -tt On Fri, Feb 1, 2013 at 11:17 PM, John Cuthbertson < [email protected]> wrote: > Hi Taras, > > I'm going to cc the serviceability alias. I think they might be best > suited to answer some of your questions. I believe they own the API and the > GC provides the data. > > Answer 1: It should be milliseconds, but there was a bug ( > http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7087969) that is now > fixed in hs24 and you could be running into that. > > Answer 2: This sounds like a bug. Do you have a test case you can share? > > Answer 3: I'll leave that to the serviceability guys. > > Regards, > > JohnC > > > On 1/28/2013 1:11 PM, Taras Tielkes wrote: > > > Hi, > > I'm playing around with the new(ish) GarbageCollectionNotificationInfo > API. We're using ParNew+CMS in all our systems, and my first goal is a > comparison between -XX:+PrintGCDetails -verbose:gc output and the actual > data coming through the notification API. I'm using Java 1.7.0u6 for the > experiments. > > So far, I have a number of questions: > 1) duration times > > The javadoc for gcInfo.getDuration() describes the returned value as > expressed in milliseconds. However, the values differ to the gc logs by > several orders of magnitude. How are they calculated? > > On a 1-core Linux x64 VM, the values actually look like microseconds, > but on a Win32 machines I still can't figure out any resemblance to gc log > timings. > > Apart from the unit, what should the value represent? Real time or user > time? > > 2) CMS events with cause "No GC" > > How exactly do the phases of CMS map to the notifications emitted for > the CMS collector? > > I sometimes get events with cause "No GC". Does this indicate a > background CMS cycle being initiated by hitting the occupancy fraction > threshold? > > 3) Eden/Survivor > > It seems that the MemoryUsage API treats Eden and Survivor separately, > i.e. survivor is not a subset of eden. This is different from the gc log > presentation. Is my understanding correct? > > In general, I think it would be useful to have a code sample for the GC > notification API that generates output as close as possible to > -XX:+PrintGCDetails -verbose:gc, as far as the data required to do so is > available. > > The API looks quite promising, it seems it could really benefit from a > bit of documentation love :) > > Thanks, > -tt > > > > _______________________________________________ > hotspot-gc-use mailing > [email protected]http://mail.openjdk.java.net/mailman/listinfo/hotspot-gc-use > > >
