RFR: CODETOOLS-7902928: Improve support for async-profiler 2.x [v2]

[Jason Zaugg]

On Mon, 10 May 2021 14:34:58 GMT, Andrei Pangin <apangin at openjdk.org> wrote:

>> jmh-core/src/main/java/org/openjdk/jmh/profile/AsyncProfiler.java line 100:
>> 
>>> 98: 
>>> 99:         OptionSpec<String> optEvent = parser.accepts("event",
>>> 100:                 "Event(s) to sample: cpu, alloc, lock, wall, itimer; com.foo.Bar.methodName; any event from `perf list` e.g. cache-misses")
>> 
>> I'd vote against making `event` a multi-option:
>> 
>> - First, not all events can be profiled together, e.g. you cannot profile `wall` and `cache-misses` at the same time. Only `alloc` and/or `lock` may be combined with other events.
>> - Second, async-profiler has dedicated options for specifying the allocation profiling interval and the lock profiling threshold, like `alloc=512k,lock=1ms`. Even though multiple `event=x` options are allowed, the canonical way to turn on allocation and lock profiling is `event=cpu,alloc[=interval],lock[=threshold]` (interval and threshold are optional).
>
> So, instead of making `event` a multi-option, my suggestion is to add `alloc` and `lock` as separate options that will be directly translated to async-profiler's peer options.

This sounds good to me. I'll implement it this way.

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PR: https://git.openjdk.java.net/jmh/pull/37