On 17/08/2016 6:57 AM, Leela Mohan wrote:
Your thoughts on this will be helpful.
Thanks,
Leela
[ Removed "serviceability-...@openjdk.net" mailing alias added
"hotspot-dev" since i am getting failed mail delivery notification ]
Added back - it is openjdk.java.net, not openjdk.net
David
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On Fri, Aug 12, 2016 at 4:33 PM, Daniel D. Daugherty <
daniel.daughe...@oracle.com> wrote:
On 8/12/16 5:27 PM, Leela Mohan wrote:
Hi Daniel,
Actually, I was thinking about the case where compiler choose not to have
complete "de-opt" state. For ex: Local pruning. I can also think of other
cases which need callback events like, posting exceptions to the agent.
JVMTI requests for examining/changing the stack frame would conservatively
de-optimize the compile methods but not all de-optimizable locations can
restore the java state user expect.
What are the expectations for VM for these cases ?
I think we'll have to wait for someone more current in how the compilers
interact with JVM/TI to chime in here. I stopped actively working on
JVM/TI back in 2010 or so... :-)
Dan
Thanks,
Leela
On Fri, Aug 12, 2016 at 4:04 PM, Daniel D. Daugherty <
daniel.daughe...@oracle.com> wrote:
On 8/12/16 4:21 PM, Leela Mohan wrote:
Hi experts,
It looks like, we don't disallow setting capabilities when VM is in
"JVMTI_PHASE_LIVE". And, I notice, for every new compilation of method,
ciEnv caches the JVMTI state and expects those assumptions to be true
during the compilation. Otherwise, dump the compiled method.
However, we don't seem to do anything with the methods which were
compiled
before setting the capability.
What is the understanding?
Thanks,
Leela
Hi Leela,
I'm guessing that you are talking about this capability:
http://docs.oracle.com/javase/8/docs/platform/jvmti/jvmti.ht
ml#jvmtiCapabilities.can_generate_compiled_method_load_events
and this event:
http://docs.oracle.com/javase/8/docs/platform/jvmti/jvmti.ht
ml#CompiledMethodLoad
The can_generate_compiled_method_load_events capability needs to be added
in order to generate CompiledMethodLoad events. Capabilities are added via
http://docs.oracle.com/javase/8/docs/platform/jvmti/jvmti.ht
ml#AddCapabilities
which can be called from different JVM/TI phases. Different VM
implementations
can require that certain capabilities can only be added in certain JVM/TI
phases.
However, if AddCapabilities() does not return a JVM/TI error when a
capability
is added in a phase, e.g., the live phase, then you can safely assume that
the capability has been added.
In your example, it sounds like the capability is added in the live phase
because you are seeing events generated for newly compiled methods. In
order
to see synthetic events for methods that were compiled before you added
the
capability, your agent needs to use a different function:
http://docs.oracle.com/javase/8/docs/platform/jvmti/jvmti.ht
ml#GenerateEvents
The documentation for Compiled Method Load has this line:
These events can be sent after their initial occurrence with
GenerateEvents.
and that sounds just like your situation.
Hope this helps.
Dan
