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

[Marcus Larsson]

Hey Max,

On 2015-12-09 18:11, Max Ockner wrote:
> 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.

A call to configure_stdout will configure logging for a particular 
tagset. It doesn't configure a bunch of tags separately. What I mean by 
this is that LogConfigure::configure_stdout(LogLevel::Info, true, 
LOG_TAGS(tag1, tag2)) is equivalent to the vm argument 
-Xlog:tag1+tag2=info. It is not the same as -Xlog:tag1=info,tag2=info 
(or alternatively -Xlog:tag1=info -Xlog:tag2=info).

Thanks,
Marcus

>
> 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
>>>
>>
>