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

[David Holmes]

On 10/12/2015 4:52 AM, Marcus Larsson wrote:
> 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).

Sorry have to ask: what is the difference between these three variants:

-Xlog:tag1+tag2=info
-Xlog:tag1=info,tag2=info
-Xlog:tag1=info -Xlog:tag2=info

I can't see a description of the + version, but I assume the bototm two 
are equivalent?

Thanks,
David

> 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
>>>>
>>>
>>
>