RFR: 8317433: Async UL: Only grab lock once when write():ing [v3]

[Johan Sjölen]

On Thu, 5 Oct 2023 10:06:31 GMT, Johan Sjölen <jsjolen at openjdk.org> wrote:

>> Hi,
>> 
>> The writer thread used to await for `_data_available` to become true through using the async log lock as a condition variable. When data is available it'd let go of the lock and then call `AsyncLogWriter::write()`, which would immediately try to acquire that same lock. We can remove this second instance by moving the work needed to be done under lock to `run`.
>> 
>> Thank you for considering this.
>
> Johan Sjölen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Rewrite comment

src/hotspot/share/logging/logAsyncWriter.cpp line 160:

> 158:         _lock.wait(0/* no timeout */);
> 159:       }
> 160:       // Only doing a swap and statistics under the lock to

@navyxliu 

The original comment was:

>`// lock protection. This guarantees I/O jobs don't block logsites.`

Does this change make sense to you?

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PR Review Comment: https://git.openjdk.org/jdk/pull/16030#discussion_r1347161523