#22 Monitor wait times

[Martin Rohla]

I think it would be very useful, to add one view, which
would show all monitors (or maybe better all monitors
with some objects waiting), and times objects spent on
them and also, from the other side, for each object the
time it has spent on different monitors. I don't know,
however, if it is possible to do this with JVMPI?
But it should be possible somehow, because i.e.
JProfiler has this ability.

[Konstantin Scheglov]

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Yes, I have this in plans. This function is fairly easy to implement, there are two JVMPI events: JVMPI_EVENT_MONITOR_WAIT and JVMPI_EVENT_MONITOR_WAITED and if it is possible to receive call stack for them (I think that this is possible, but not test this), I will able to implement needed functionality.
One thinng to discuss is what is here "object". From my point of view object is call stack, i.e. place where wait was called. How do you think?

[Martin Rohla]

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Yes, I think call stack would be great..

[Nobody/Anonymous]

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I think that two different modes of operation would be
interesting for monitor-profiling. One where call stacks are
used to see where a monitor becomes locked/are locked and
another one that only shows what monitors are the expensive
ones (how many 'thread-milliseconds' each monitor blocks).
The latter one could probably be made not to cause as much
application slowdown as the former one.