RFR: 8190346: improve unified JVM logging help message and warnings

Marcus Larsson marcus.larsson at oracle.com
Thu Feb 22 15:34:34 UTC 2018


Hi,

Please review the following patch to improve the -Xlog help and warning 
messages.

The changes include:

  * Attempt to find and give suggestions for log selections that don't
    match any tag sets. For example, when passing "-Xlog:load" issue a
    warning similar to the following: "No tag set matches selection
    'load'. Did you mean any of the following? load* class+load
    module+load".
  * Change log level for almost all startup logging on 'logging' tag
    from trace/debug to info level. These are log messages that are only
    printed once during startup, so it makes little sense in obscuring
    them under debug/trace. The all tag set listing is only moved from
    trace to debug, though.
  * Make LogConfiguration::print_command_line_help() take an
    outputStream* instead of FILE*, to better align it with various
    describe/print_on functions.
  * Add descriptions of log file output related options to -Xlog:help
    output.
  * Print 'none' if there are no decorations configured for an output
    (instead of just printing nothing).

Issue:
https://bugs.openjdk.java.net/browse/JDK-8190346

Webrev:
http://cr.openjdk.java.net/~mlarsson/8190346/webrev.00

Tested with hs-tier 1-2, and locally with 
test/hotspot/jtreg/{runtime,serviceability,gc}/logging.

Thanks,
Marcus



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