RFR: 8284849: Add deoptimization to unified logging

[Johan Sjölén]

On Mon, 23 May 2022 07:22:10 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> This PR adds a new "deoptimization" tag and a new log message on the info level mimicking JFR's deoptimization event. In the future this tag will be used to add trace level information, hopefully replacing TraceDeoptimization. JFR's event also captures the stacktrace, which this does not (happy to add this if considered important).
>> 
>> An example output looks like this: 
>> 
>> 
>> [1.346s][info][deoptimization] Deoptimization start {
>> [1.346s][info][deoptimization]   compileId = 407
>> [1.346s][info][deoptimization]   compiler = c2
>> [1.346s][info][deoptimization]   method:lineno:bci = java.util.concurrent.locks.ReentrantLock$Sync.tryRelease(I)Z:176:26
>> [1.346s][info][deoptimization]   instruction = ifne
>> [1.346s][info][deoptimization]   reason = unstable_if
>> [1.346s][info][deoptimization]   action = reinterpret
>> [1.346s][info][deoptimization] } Deoptimization end
>
> src/hotspot/share/runtime/deoptimization.cpp line 1937:
> 
>> 1935:     if(Log(deoptimization)::is_info()) {
>> 1936:       LogMessage(deoptimization) lm;
>> 1937:       auto tm = trap_method();
> 
> Not sure use if C++11 type inference is a permitted use - I can't find it n the style guide.

`LogMessage` ensures that messages are kept in order in the final output, but this is not needed if we're logging on one line as Jorn has suggested. I'm also removing the type inference.

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PR: https://git.openjdk.java.net/jdk/pull/8812