review request (S): 8057531: refactor gc arg processing code slightly

[Mikael Gerdin]

Hi John,

On Thursday 04 September 2014 02.30.25 John Coomes wrote:
> Please review this small refactoring of gc argument processing code:
> 
> http://cr.openjdk.java.net/~jcoomes/8u/8u40/8057531-refactor-gc-arg-proc/

I'm by no means an expert on the argument processing code but this ĺooks like 
a good cleanup.

I noticed that the conditions for ending up in 
1537     if (should_auto_select_low_pause_collector()) {

from 
1541     if (!UseSerialGC &&
1542         !UseConcMarkSweepGC &&
1543         !UseG1GC &&
1544         !UseParNewGC &&
1545         FLAG_IS_DEFAULT(UseParallelGC)) {

to
 611   return UseConcMarkSweepGC || UseG1GC || UseParallelGC || 
UseParallelOldGC ||
 612     UseParNewGC || UseSerialGC;
 613 }

I think that's a good change.

Before your change it seems like setting -XX:+UseParallelOldGC could still end 
up in should_auto_select_low_pause_collector since set_parallel_gc_flags() was 
called after set_ergonomics_flags() and the condition only looked at 
UseParallelGC.

The change overall looks ok to me, but I'm not a 8u Reviewer.

/Mikael

> 
> Thanks for any feedback. 
> 
> -John