On 16 maj 2014, at 10:59, Mario Torre <neug...@redhat.com> wrote: > On Fri, 2014-05-16 at 09:12 +0200, Staffan Larsen wrote: > > Hello Staffan, > > Thanks for the quick reply. > >> JEP 167 is done and should be in the completed state. I’ll see if I >> can get that updated. The relevant bug (with change set information) >> is: https://bugs.openjdk.java.net/browse/JDK-8005849. > > Great, yeah, updating the page seems a good idea :)
The mercurial text file has been updated, but the publishing script is broken so the web-page won’t be updated (I don’t expect this to be fixed until JEP 2.0 is final). > >> For seeing what instrumentation has been added, take a look at >> src/share/vm/trace/trace.xml which lists all instrumentation points. >> To enable trace output in OpenJDK, run with q (although running Java >> Flight Recorder [1] from Java Mission Control [2] provides a much >> better user experience). > > I see, thanks. It would be nice to also have some documentation how to > get those traces, for instance, assuming I want to turn on/off a > specific trace, and I want to attach my own agent, how would I do this? > > I guess I can figure it out somehow from the code, but it's not obvious > if those traces can be used other than via the target vm printing stuff. > > I understand Flight Recorded is able to access this information, but > what if I want to write my own agent? Is this accessed via JVMTI, or > JMX, or is there another way (perhaps less expensive)? There is currently no way to access the information outside of Flight Recorder (or -XX:+EnableTracing in OpenJDK). > > A final question, do you know the impact when instrumentation is turned > on (I can do my one testing, but maybe there are some official numbers > around already :)? For Flight Recorder we see a performance overhead of around 2-3%. > >> Regarding the broken links, it looks like the >> http://opengrok.neojava.org is no longer what it used to be. In >> general, page you refer to has not been updated for several years... > > Hmm, I believe this should be updated as well, it's a pretty important > page and I think the first place anyone interested in serviceability > would look at, what do you think? That would be good. I don’t know who can edit the page. /Staffan > > Cheers, > Mario >
