RFR (XS): 8025605: G1: Heap expansion logging misleading for fully expanded heap

[Thomas Schatzl]

Hi Bengt,

On Fri, 2013-09-27 at 21:57 +0200, Bengt Rutisson wrote:
> 
> Hi everyone,
> 
> Could I have a couple of reviews for this small change?
> 
> http://cr.openjdk.java.net/~brutisso/8025605/webrev.00/
> 
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8025605
> 
> Background:
> 
> When running G1 with -XX:+PrintAdaptiveSizePolicy some information
> about the heap sizing is logged. When the heap is fully expanded but
> the ergonomics would have liked to expand even more the following
> message is logged: 
> 
> [G1Ergonomics (Heap Sizing) did not expand the heap, reason: heap
> expansion operation failed] 
> 
> It sounds like something failed, but in reality we just hit the -Xmx
> value. We should have a more informative message that does not look
> like a serious failure. 
> 
> With my suggested patch the message will instead be:
> 
> [G1Ergonomics (Heap Sizing) did not expand the heap, reason: heap
> already fully expanded] 
> 

I would somewhat actually prefer if the message were moved after the
message printed in line 1787. Otherwise this message would be different
to others if verbosity is high enough. I.e. missing the "expand the
heap" message with the two sizes message.

Also, could you remove the assignment to the local variable
old_mem_size? I think the variable is unused. (As a bonus you could
remove the same assignment to a local "old_mem_size" variable in
shrink_helper too :)

Thanks,
  Thomas