RFR(S) JDK-8025526: VirtualSpace should support per-instance disabling of large pages

[Thomas Schatzl]

Hi Mikael,

On Mon, 2013-09-30 at 12:49 +0200, Mikael Gerdin wrote:
> Erik,
> 
> On 09/27/2013 05:10 PM, Erik Helin wrote:
> > Hi Mikael,
> >
> > what do you think about splitting the VirtualSpace::initialize method
> > into two methods:
> > - VirtualSpace::initialize
> > - VirtualSpace::initialize_with_granularity
> >
> > Then initialize would just call initialize_with_granularity like the
> > following:
> >
> >    bool VirtualSpace::initialize(ReservedSpace rs, size_t committed_size) {
> >      size_t granularity = os::page_size_for_regions(rs.size(), rs.size(), 1);
> >      return initialize_with_granularity(rs, committed_size, granularity);
> >    }
> >
> >    bool VirtualSpace::initialize_with_granularity(ReservedSpace rs,
> >      size_t committed_size, size_t granularity) {
> >      assert(granularity > 0, "Can't have 0 as granularity");
> >      // old initialize code
> >      _middle_alignment = granularity;
> >      // rest of old initialized code
> >    }
> >
> > This way, we get rid of the default argument and don't have to check if
> > max_commit_granularity == 0.
> 
> I like your suggestion.
> I've uploaded a second webrev which implements your suggestion.

Could the patch changed to remove the default parameter specification
for the max_commit_granularity parameter in
initialize_with_granularity()? 

The code basically checks that the given granularity is >0, so a default
value of 0 invites errors.

> I had to update the test code so I re-ran the tests on all platforms.
> 
> New webrev: http://cr.openjdk.java.net/~mgerdin/8025526/webrev.1/

Looks good otherwise.

Thanks,
  Thomas