Profile the lock usage in openjdk

[Jeremy Manson]

Of course, if all you want is a coarse measurement, you can use JVMTI.
 Just have a timer that starts at the first one of these, and stops at the
second:

http://docs.oracle.com/javase/7/docs/platform/jvmti/jvmti.html#MonitorContendedEnter
http://docs.oracle.com/javase/7/docs/platform/jvmti/jvmti.html#MonitorContendedEntered

We instrument these on a sampling basis across large numbers of
invocations.  It doesn't perturb the application behavior too much.

Jeremy


On Mon, Mar 3, 2014 at 8:14 PM, David Holmes <david.holmes at oracle.com>wrote:

> On 4/03/2014 1:48 PM, Junjie Qian wrote:
>
>> Dear all,
>>
>> I am one graduate student working on Java VM, and would like to study the
>> multithread in Java benchmarks. The information I want to get is the lock
>> contentions in the benchmark, such as fatlock/thinLock/SpinLock number, or
>> the time spent on waiting for these lock.
>>
>> Could you give me some advices on this, as how to insert code in openjdk
>> to get such info?
>>
>
> You will find that there is already a lot of information gathered within
> the VM, but some probably only for non-product builds and most only for the
> contention case where the monitor is inflated. The problem with overly
> instrumenting the lock code to "measure" contention is that the
> instrumentation code completely changes the contention patterns. Adding
> additional instrumentation is non-trivial as you need to handle both
> interpreted and JIT'd code.
>
> David
>
>
>  Thanks!
>> Best
>> Junjie
>>
>>