RFR: 8152635: Create a UL class to represent a Log + Level combination

[Robbin Ehn]

Hi Stefan, looks good to me.

(we can now also remove the ResourceMark from the other two test, right?)

/Robbin

On 03/29/2016 03:46 PM, Stefan Karlsson wrote:
> Hi all,
>
> Please review this patch to introduce a Unified Logging class to
> describe a combination of a tagset and a log level.
>
> http://cr.openjdk.java.net/~stefank/8152635/webrev.01
> https://bugs.openjdk.java.net/browse/JDK-8152635
>
> The patch is applied on top of the patch in:
> http://mail.openjdk.java.net/pipermail/hotspot-dev/2016-March/022302.html
>
> With this class we could write code as:
> LogTarget(Debug, gc, heap) log;
> if (log.is_enabled()) {
>    log.print(...);
>    log.print(...);
>    ... = log.stream();
> }
>
> instead of the current model:
> Log(gc, heap) log;
> if (log.is_debug()) {
>    log.debug(...)
>    log.debug(...)
>    ... = log.debug_stream():
> }
>
> The LogTarget class/macro ensures that we only mention the log level
> once, so that we don't accidentally log to the wrong level. The previous
> version forces the coder to repeat 'debug' four times.
>
> One example where the wrong log level has been used:
> https://bugs.openjdk.java.net/browse/JDK-8152962
>
> I've converted one function in compactibleFreeListSpace.cpp to show how
> to use the new class.
>
> Test: new internal vm test, jprt
>
> Thanks,
> StefanK