> On May 27, 2015, at 12:34 AM, Peter Levart <peter.lev...@gmail.com> wrote: > > Hi Dmitry, > > The jdk part looks OK (no great changes on this side from last webrev). Is > there a particular reason why the return type of printFinalizayionQueue() > method is Object[] and not Map.Entry<String, int[]>[] ? >
Taking it further - is it simpler to return String[] of all classnames including the duplicated ones and have the VM do the count? Are you concerned with the size of the String[]? > For the hotspot part, I have a few reservations. You expect that the type of > array elements will be HashMap.Node and that the key/value fields will be at > fixed offsets. Is this even true for all architectures (32bit, 64bit > +-UseCompressedOops)? > > The type of HashMap entry is controlled by code in HashMap which has a long > history of changes. Next time the implementation of HashMap changes, your > code could break. Would it be possible to only use public API? To invoke > methods on Map.Entry interface to obtain the key and value? > Indeed, depending on the HashMap internal implementation is a bad idea. Mandy > Regards, Peter > > On 05/26/2015 04:16 PM, Dmitry Samersoff wrote: >> Hi Everybody, >> >> http://cr.openjdk.java.net/~dsamersoff/JDK-8059036/webrev.09/ >> >> Please review updated webrev - >> >> printFinalizationQueue now returns and array of Map.Entry<String, int[]) >> and all formatting is done on VM side. >> >> -Dmitry >> >> On 2015-05-21 02:07, Mandy Chung wrote: >>>> On May 19, 2015, at 11:51 PM, Dmitry Samersoff >>>> <dmitry.samers...@oracle.com <mailto:dmitry.samers...@oracle.com>> wrote: >>>> >>>> Other alternatives could be to do all hashing/sorting/printing on native >>>> layer i.e. implement printFinalizationQueue inside VM. >>>> >>>> Both options has pros and cons - Java based solution requires less JNI >>>> calls and better readable but takes more memory. >>>> >>>> It might be better to return an array of Map.Entry<String, int[]> >>>> objects to VM rather than one huge string. >>> The output and formatting should be done by jcmd. What you really need >>> to get a peek on the finalizer queue and print the histogram. The VM >>> has the heap histogram implementation. Have you considered leveraging >>> that? >>> >>> 5: 1012 40480 java.lang.ref.Finalizer >>> >>> You can find the registered Finalizer instances. The downside is that >>> icmd -finalizerinfo stops the world. I think it’s not unreasonable for >>> this diagnostic command to be expensive like -heap command. >>> >>> Mandy >> >
