RFR: 8142979: Add programmatic enable/disable methods to Unified Logging

[Max Ockner]

Hello Marcus,

I looked over your code in logConfiguration.cpp

What is the purpose of limiting the number of tags that can be 
configured through a given call to configure_stdout? I understand that 
previously any change made to the configuration would have reset it 
entirely, and as a result you could restrict the number of tags in the 
configuration.  I can't tell if you want to restrict the number of tags 
in the configuration or the number of tags processed by 
configure_stdout, because those restrictions are no longer equivalent 
now that you can configure_stdout can add to the configuration without 
clearing it.

This question also applies to the handling of multiple Xlog options.

Thanks,
Max


On 12/1/2015 3:03 AM, Marcus Larsson wrote:
>
>
> On 2015-11-30 19:40, Coleen Phillimore wrote:
>>
>> I'm confused how this API works.
>>
>> http://cr.openjdk.java.net/~mockner/classunload/src/share/vm/prims/jvmtiEnv.cpp.sdiff.html 
>>
>>
>> I imagine we'd want to do:
>>
>> if (value != 0) {
>>   LogConfiguration::configure_stdout(info, true, classunload);
>> } else {
>>   LogConfiguration::configure_stdout(off, true, classunload);
>> }
>>
>> ???
>
> Yes, except you would need to pass the classunload tag with the 
> LOG_TAGS macro, so it'd be:
>
> if (value != 0) {
>   LogConfiguration::configure_stdout(LogLevel::Info, true, 
> LOG_TAGS(classunload));
> } else {
>   LogConfiguration::configure_stdout(LogLevel::Off, true, 
> LOG_TAGS(classunload));
> }
>
> and that would be the same as passing -Xlog:classunload=info and 
> -Xlog:classunload=off
>
> Regards,
> Marcus
>
>> Thanks,
>> Coleen
>>
>>
>> On 11/25/15 7:13 AM, Marcus Larsson wrote:
>>> Hi,
>>>
>>> Please review the following patch adding support for configuration 
>>> of the stdout unified logging output from within the VM itself.
>>>
>>> The patch adds the configure_stdout() function, allowing a set of 
>>> tags to be set to the given level on stdout.
>>> To disable logging the level is simply specified as LogLevel::Off.
>>>
>>> The patch depends on the fix for 8142952 [0] that's currently out on 
>>> review, so the configuration is correctly aggregated rather than reset.
>>>
>>> Webrev:
>>> http://cr.openjdk.java.net/~mlarsson/8142979/webrev.00/
>>>
>>> Issue:
>>> https://bugs.openjdk.java.net/browse/JDK-8142979
>>>
>>> Thanks,
>>> Marcus
>>>
>>> [0]: https://bugs.openjdk.java.net/browse/JDK-8142952
>>
>