JEP 271: Unified GC Logging - Second pre-review

[charlie hunt]

> On Nov 11, 2015, at 10:07 AM, Kirk Pepperdine <kirk.pepperdine at gmail.com> wrote:
> 
> Hi Charlie,
> 
>> 
>> To be quite honest, my motivation for jumping in on this thread was to highlight that there are many use cases where manually looking logs are useful, i.e. GC log information shouldn’t be tailored only for tooling. It should also be easily human readable too.
>> 
>> In other words, both general uses are useful, needed, and should be accounted for in Bengt’s unified GC logging implementation.
> 
> Sure, but IME people simply don’t read them. I ask people to read them in my workshop and they still avoid doing so. That said, I’ve not been suggesting the logs be completely unreadable. I still read individual events myself. However, I am still concerned about the overall gross effects of the UL from all sources (not just GC) on JVM performance. IME, logging frequency is the #1 problem that I often run into. This gets especially bad if there is a lock involved. #2 is bulk and even worse, bulk and frequency are often combined.

I’m not surprised people don’t read them. It’s hard to get anyone to look at, or do something they feel uncomfortable with. 

As for the performance, I’m confident (and comfortable) that between Bengt and the performance team that the overhead of logging is something that will be closely monitored. Areas at risk can be prototyped, measured and mitigated before committed.

>> 
>> It is probably also worth saying that whatever the ending implementation looks, there will likely be someone who will not be happy with it. :-]
> 
> Indeed… the format suggest does solve a number of problems so in general it is a step up from what we have so good enough. However the current format does increase logging frequency so if it’s no trouble to reduce it, I think we should. I’ll be measuring the effect as soon as I get a build.

Having additional eyes and performance results is always good. :-)

thanks,

charlie

> 
> Regards,
> Kirk
>