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

[Max Ockner]

Marcus,
Did you do any testing for this change? I couldn't tell from your webrev 
or email.
Thanks,
Max

On 12/10/2015 8:15 AM, Marcus Larsson wrote:
>
> On 2015-12-10 11:28, David Holmes wrote:
>> On 10/12/2015 7:12 PM, Marcus Larsson wrote:
>>> Hi,
>>>
>>> On 2015-12-10 06:08, David Holmes wrote:
>>>> 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
>>>
>>> This will enable messages tagged with tag1 *and* tag2, like for 
>>> example:
>>>
>>> log_info(tag1, tag2)("msg");
>>>
>>> Messages tagged with only one of these tags will not be configured.
>>
>> Ah I see. Where does the end user find out about this?
>
> Currently I think it's only described in the JEP.
>
> It should probably be explained better in the -Xlog:help output.
>
> Regards,
> Marcus
>
>
>>
>> Thanks,
>> David
>> -----
>>
>>
>>>> -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?
>>>
>>> Yes, these two are equivalent now. They enable messages tagged either
>>> with tag1 *or* tag2. It doesn't enable the combination of the two.
>>>
>>> Regards,
>>> Marcus
>>>
>>>>
>>>> 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
>>>>>>>>
>>>>>>>
>>>>>>
>>>>>
>>>
>