10 RFR: 8175221: Cleanup DirtyCardQueueSet::concatenate_log

[Kim Barrett]

Need a second reviewer.

> On Feb 19, 2017, at 4:38 PM, Kim Barrett <kim.barrett at oracle.com> wrote:
> 
> Please review this simplification of concatenate_log and removal of
> some thereby unused public functions from DirtyCardQueue.
> 
> We change concatenate_log to call flush, rather than inlining more or
> less equivalent code.  The flush is conditional on the queue
> containing any data, as we prefer to leave an empty buffer in place in
> the queue when concatenating.
> 
> We also changed flush to support this; flush was a nop when the queue
> is "permanent", which is not what we want for concatenate_log.  This
> behavior was because flush was called by the queue destructor, and
> performing a flush when destroying the shared queue for a set was
> problematic.  However, JDK-8048949 changed things so that only the
> DirtyCardQueue destructor called flush, and only if the queue is
> non-permanent.  So the permanent check in flush is no longer needed,
> and removing it makes it suitable for use by concatenate_log.
> 
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8175221
> 
> Webrev:
> http://cr.openjdk.java.net/~kbarrett/8175221/hotspot.00/
> 
> Testing:
> jprt