RFR: 8140348: Convert TraceSafepoint to Unified Logging

[Claes Redestad]

On 2015-11-02 23:35, David Holmes wrote:
>> See the review thread for RFR: 8139564: Convert TraceDefaultMethods to
>> Unified Logging
>>
>> http://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2015-October/016059.html 
>>
>>
>>
>> Yes, we discussed this and decided to make all flags product pending any
>> problems discovered at a later time in the jdk9 release cycle.    Rachel
>> is doing performance testing on each flag individually as converted, but
>> we could do a run at the end of the first set to be migrated, and see if
>> there are problems then.
>
> I'm concerned about the cumulative effects. I'm also concerned that 
> even for non-product flags the logging will now have overheads in the 
> product builds.
>
> David 

I share David's concern.

Did the previous discussion miss the log_develop method (defined in 
hotspot/src/share/vm/logging/log.hpp and introduced by the UL JEP)? This 
should properly elide logging code from product builds, and seems
like the appropriate choice when moving develop flags to UL (unless 
there's a real world story for making the specific logging hit product).

I haven't seen serviceability indicate that this capability will be 
removed or enable such logging in product builds. From the JEP:

"Each log message has a logging /level/ associated with it. The 
available levels are |error|, |warning|, |info|, |debug|, |trace| and 
|develop| in increasing order of verbosity. The |develop| level is only 
available in non-product builds."

/Claes