RFR: 8267517: async logging for stdout and stderr

[Xin Liu]

On Wed, 27 Oct 2021 08:22:12 GMT, Xin Liu <xliu at openjdk.org> wrote:

> This patch refactors LogFileStreamOutput so stdout/stderr can support support -Xlog:async.
> LogFileStreamOutput::flush() is virtual. 
> 
> With  `-Xlog:all=trace:stdout`, the helloworld in Java outputs 16520 log entries to stdout.  We are see that the wall time reduces from  86.977ms to 72.436ms, or the throughput increases 20% because of async logging.
> 
> 
> $perf stat -r 300 ./build/linux-x86_64-server-release/images/jdk/bin/java -Xlog:all=trace:stdout -Xlog:async -XX:AsyncLogBufferSize=48M HelloWorld > /dev/null
> 
>  Performance counter stats for './build/linux-x86_64-server-release/images/jdk/bin/java -Xlog:all=trace:stdout -Xlog:async -XX:AsyncLogBufferSize=48M HelloWorld' (300 runs):
> 
>             112.59 msec task-clock                #    1.554 CPUs utilized            ( +-  0.15% )
>              1,517      context-switches          #    0.013 M/sec                    ( +-  0.61% )
>                  1      cpu-migrations            #    0.010 K/sec                    ( +-  4.80% )
>              4,014      page-faults               #    0.036 M/sec                    ( +-  0.01% )
> ...
>           0.072436 +- 0.000135 seconds time elapsed  ( +-  0.19% )
> 
>  Performance counter stats for 'java -Xlog:all=trace:stdout  HelloWorld' (300 runs):
> 
>              90.73 msec task-clock                #    1.043 CPUs utilized            ( +-  0.11% )
>                318      context-switches          #    0.004 M/sec                    ( +-  0.32% )
>                  1      cpu-migrations            #    0.009 K/sec                    ( +-  4.80% )
>              4,010      page-faults               #    0.044 M/sec                    ( +-  0.00% )
> ...
>          0.0869777 +- 0.0000979 seconds time elapsed  ( +-  0.11% )
> 
> 
> In this patch, we also fold two locks(RotationLocker and FileLock) of LogFileOutput into one. FileLocker now can protect _stream from multiplexing and log rotation.  The other change is that AsyncLog writing doesn't require any lock protection because it's single-threaded. 
> 
> Add a new jtreg to cover a scenario that the blocked stdout doesn't freeze the JVM application.

Hello, 
May I ping this?

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PR: https://git.openjdk.java.net/jdk/pull/6132