Does Equinox collect metrics around ClassLoading?

[guw]

Is there a way to gather class loading statistics from Equinox?

I am looking for:

• number of classes loaded (since the framework was launches)
• total time spent loading classes (since the framework was launches)

The documentation mentions such an adapter but it looks like the code has been deleted in Luna?

The ClassLoaderStatsHook mentioned in the documentation also seems to no longer exist. I was able to find StatsManager in Git history. Got the functionality purged completely without replacement?

[tjwatson]

This got removed a very long time ago when the adapter hooks got removed in 8d99169

There has not been any effort to build something back into the framework. Although I would advocate it not be built into the framework and instead provided by a system bundle fragment instead.

[guw]

Thanks @tjwatson.

For a bit more context, it's not an Eclipse application. It's more like an app server application where a single web app gets deployed as bundle. Web apps can be a composition a bundle and fragments with thousands of entries in Bundle-Classpath header. We recently change the granularity of jars (significantly), which led to a significant increase in start time. That's what I am investigating.

For example, one discover we made during the exercise was that external:/absolute/path/to/folder performs much worse then relative/path/to/folder. Have not profiled into details why, though.

[tjwatson]

When you say 1000s of entries, you mean a comma separated list of thousands of JARs? If so then the osgi.bundlefile.limit will likely have a big impact with its default of 100. It would mean for each class load on a bundle it may need to open/close a 1000 bundle files to keep the limit of 100 concurrently opened bundle files JARs. You may want to try disabling that or bump it up significantly. You disable it by setting the system property (config.ini) value osgi.bundlefile.limit=0.

[guw]

Confirming. We use osgi.bundlefile.limit=0.

[tjwatson]

OK, then not sure what the issue is. The same scenario in https://www.eclipse.org/forums/index.php?t=msg&th=1111465&goto=1854519& raising the limit helped out.

[guw]

I am not suspecting there is an issue in Equionx. The reason I want the stats is to have more data for comparison and analysis. There are "interesting" things happening inside the webapp, some of which may be impacted directly by classpath size. Thus, the data is more helpful to rule out Equinox as an issue in this case.

[akurtakov]

You may want to give a try to systemtap-java https://developers.redhat.com/blog/2014/01/10/probing-java-w-systemtap#basic_usage