RFR: 8267517: async logging for stdout and stderr [v5]

[Xin Liu]

> This patch refactors LogFileStreamOutput so stdout/stderr can support support -Xlog:async.
> 
> With  `-Xlog:all=trace:stdout`, the helloworld in Java outputs 16520 log entries to stdout.  We are see that the wall time reduces from  84.138ms to 72.914ms, or the throughput increases 15% 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):
> 
>             107.21 msec task-clock                #    1.470 CPUs utilized            ( +-  0.17% )
>              2,681      context-switches          #    0.025 M/sec                    ( +-  0.32% )
>                  1      cpu-migrations            #    0.011 K/sec                    ( +-  4.56% )
>              4,006      page-faults               #    0.037 M/sec                    ( +-  0.01% )
> ...
>           0.072914 +- 0.000126 seconds time elapsed  ( +-  0.17% )
> 
>  Performance counter stats for './build/linux-x86_64-server-release/images/jdk/bin/java -Xlog:all=trace:stdout -XX:AsyncLogBufferSize=48M HelloWorld' (300 runs):
> 
>              88.04 msec task-clock                #    1.046 CPUs utilized            ( +-  0.10% )
>                310      context-switches          #    0.004 M/sec                    ( +-  0.31% )
>                  1      cpu-migrations            #    0.008 K/sec                    ( +-  5.07% )
>              4,004      page-faults               #    0.045 M/sec                    ( +-  0.01% )
> ...
>           0.084138 +- 0.000111 seconds time elapsed  ( +-  0.13% )
> 
> 
> The easiest test of stdout with AsyncLogging is to use tty and XOFF Ctrl^s. Java applications with UL to stdout were blocked by Ctrl-s. The entire java process will be frozen.  -Xlog:async now cover both stdout and stderr. It can circumvent this issue.  
> 
> Add a new jtreg to cover a scenario that unified logging with -Xlog:async will not be frozen even when stdout is blocked.

Xin Liu has updated the pull request incrementally with one additional commit since the last revision:

  Remove BlockedLoggingTest.java and add test for stdout/err in test_asynclog.cpp.
  
  This patch also adds to flushing semantic to LogFileStreamOutput::write_blocking().
  It aligns with LogFileOutput::write_blocking().

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6132/files
  - new: https://git.openjdk.java.net/jdk/pull/6132/files/769110a2..eed6f8ad

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6132&range=04
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6132&range=03-04

  Stats: 242 lines in 5 files changed: 62 ins; 169 del; 11 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6132.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6132/head:pull/6132

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