RFR: 8216064: -XX:StartFlightRecording:settings= doesn't work properly

[Erik Gahlin]

Hi,

Could I have a review of "8216064: -XX:StartFlightRecording:settings= 
doesn't work properly"

The change fixes three problems:

1. If a user specifies -XX:StartFlightRecording:settings=<filename> 
where <filename> is shorter than four characters a cryptic error message 
is written, for example "begin 0, end -2, length 2".

2. If a user specifies -XX:StartFlightRecording:setttings=<filename> and 
the file doesn't exist, it results in the error message "Could not parse 
setting <filename>" which is confusing since a file that doesn't exists 
can't be parsed.

3. If a user specifies -XX:StartFlightRecording the default 
configuration is used (default.jfc), which is convenient, but there is 
no way to opt-out of settings all together. This is useful when you want 
to make your own Java events and not get the recording fille with 
JVM/JDK events This is now made possible with 
-XX:StartFlightRecording:settings=none.

Bug:
https://bugs.openjdk.java.net/browse/JDK-8216064

Webrev:
http://cr.openjdk.java.net/~egahlin/8216064.1/

Testing:
test/jdk/jdk/jfr/*

Thanks
Erik