RFR (L): 8046148: JEP 158 Unified JVM Logging

[Marcus Larsson]

Hi,

On 2015-09-22 20:55, Rachel Protacio wrote:
> Hi,
>
> I believe that utilities/ostream.cpp#logStream::write() needs to have 
> a line at the end
>
>    update_position(s, len);
>
> As it stands, the code updates the _position variable that belongs to 
> the stringStream _current_line (via the _current_line.write() 
> function), but the logStream _position does not get updated. This was 
> causing problems for me as I tried to make use of the 
> outputStream::indent() function.
>

Good catch, I'll add that.

Thanks,
Marcus

> Thanks,
> Rachel
>
> On 9/7/2015 9:33 AM, Marcus Larsson wrote:
>> Hi,
>>
>> Please review the following patch adding the unified logging 
>> framework to hotspot.
>>
>> JEP:
>> https://bugs.openjdk.java.net/browse/JDK-8046148
>>
>> Webrev:
>> http://cr.openjdk.java.net/~mlarsson/8046148/webrev.00/
>>
>> See the JEP description for a general overview of the new feature. 
>> Below are some notes on the implementation.
>>
>> The patch adds the new 'share/vm/logging' subdirectory containing the 
>> unified logging framework. The main entry point is log.hpp, which 
>> contains the necessary macros and definitions to use the framework.
>>
>> Log tags are defined/listed in logTag.hpp, and are passed as template 
>> arguments to the Log class. Every combination of tags used in a log 
>> call has a corresponding LogTagSet instance, which keeps a track of 
>> all the outputs it should write the log message to (and their 
>> levels). Having tags as template arguments allows mapping directly 
>> from a set of tags to the LogTagSet instance, which means that the 
>> overhead for disabled logging should be low. Currently each log 
>> message can be tagged with up to 5 tags, but this can be increased if 
>> ever required (and with C++11's variadic templates the limit can be 
>> removed completely).
>>
>> The LogConfiguration class keeps track of configured outputs (stdout, 
>> stderr, and possible file outputs). Configuration is done either by 
>> command line arguments (-Xlog) or by DCMD. Both methods will in turn 
>> use the LogConfiguration class to perform the parsing & 
>> configuration. This configuration includes iterating over all 
>> LogTagSet instances and updating them accordingly. The 
>> LogTagLevelExpression class is used to represent the selection of 
>> tags and levels for a given configuration request (the 
>> "what"-expression).
>>
>> The LogDecorators class contains a selection of decorators. Instances 
>> of this class is kept in LogTagSet to track what decorators to use 
>> (this is the union of all decorators used by its outputs). Each log 
>> call will create a LogDecorations instance (note: different classes), 
>> which will contain the actual decoration strings for the log message. 
>> These decorations are used for each output the tagset is set to log 
>> on, and are then discarded.
>>
>> The LogPrefix class allows messages of specific sets of tags to be 
>> prefixed. The prefix should supply a printf-style format with 
>> argument. (This allows GC logging to prefix messages of certain 
>> tagsets with GCId.) Prefixes are implemented using template 
>> specializations based on the specified tags, with the 
>> general/unspecialized case giving an empty prefix.
>>
>> The LogOutput class defines the interface for all types of log 
>> outputs. LogFileStreamOutput corresponds to FILE* stream based log 
>> outputs. LogFileOutput builds on this and adds the file management 
>> and log rotation support.
>>
>> A simple jtreg test is included in this patch. Additional tests will 
>> be added at a later stage.
>>
>> Thanks,
>> Marcus
>