Contribution: Lock Contention Profiler for HotSpot

[Peter Hofer]

Hi Andrew,

On 11/04/2016 12:14 PM, Andrew Dinn wrote:
>> We described our profiler in more detail in a research paper at ICPE
>> 2016. [1] In our evaluation, we found that the overhead is typically
>> below 10% for common multi-threaded Java benchmarks. Please find a free
>> download of the paper on our website:
>
> Have you measured the overhead this change produces when running with
> contention detection disabled? (i.e. do we pay to have this feature even
> when we don't use it).

We measured only the overhead relative to an unmodified OpenJDK build.

Our profiler observes only lock contention, which is generally handled 
via slow paths in the VM code, so this is where we added the code to 
record events. I don't expect this code to cause much overhead when 
disabled. However, we added fields to several data structures, which 
might make a difference.

I'll run some more benchmarks and report my findings.

Cheers,
  Peter