RFR: 8269022: Put evacuation failure string directly into gc=info log message [v4]

[Albert Mingkun Yang]

On Mon, 5 Jul 2021 11:59:22 GMT, Thomas Schatzl <tschatzl at openjdk.org> wrote:

>> Hi all,
>> 
>>   can I have reviews for this change that puts the evacuation failure marker from a separate log line into the GC timing message. I.e. instead of
>> 
>> 
>> Pause Young (Normal) (G1 Evacuation Pause)
>> To-space exhausted
>> 
>> into
>> 
>> 
>> Pause Young (Normal) (Evacuation Failure) (G1 Evacuation Pause) 
>> 
>> 
>> This is imho easier to read, better to process and less wasteful with log space.
>> 
>> Testing: tier1, gc/g1 tests
>
> Thomas Schatzl has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix G1AllowPreventiveGC -> G1UsePreventiveGC

Regarding `Pause Young (Normal) (Evacuation Failure) (G1 Evacuation Pause)`, I interpret the three pairs of parens as:


1. (<gc pause kind, deciding what should be done in this pause>)
2. (<sth unexpected happened, deviating from the original plan>)
3. (<what initiates this pause>)

2 occurs strictly later than 1&3, so a more natural order is

`Pause Young (Normal) (G1 Evacuation Pause) (Evacuation Failure)`.

This way, the original structure (meaning of the first two pairs of parens) could be preserved in all cases. When sth unexpected happens, the log is only appended, leaving the "conceptually existing" part intact.

Ofc, this is very subjective; just my 2 cents. (Merely a comment, not a review. I am fine with the current change.)

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PR: https://git.openjdk.java.net/jdk/pull/4539