RFR (S) 8220350: Refactor ShenandoahHeap::initialize

[Aleksey Shipilev]

On 3/8/19 7:45 PM, Zhengyu Gu wrote:
> On 3/8/19 12:14 PM, Aleksey Shipilev wrote:
>> Fix:
>>    http://cr.openjdk.java.net/~shade/8220350/webrev.01/
> 
> With large pages, there is a possibility that a single page can host multiple regions. Our region
> based commit/uncommit might not work in this scenario. Have you tested it?

This is handled already by rounding up region size to page size in ShenandoahHeapRegion::setup_sizes
(yes, it is awkward, but well...):

  // Make sure region size is at least one large page, if enabled.
  // Otherwise, uncommitting one region may falsely uncommit the adjacent
  // regions too.
  // Also see shenandoahArguments.cpp, where it handles UseLargePages.
  if (UseLargePages && ShenandoahUncommit) {
    region_size = MAX2(region_size, os::large_page_size());
  }

I think it is tested by one of our regression tests.

> SH::initialize() still a 200 lines function, might be good to break it up, e.g. a method for each
> section? Otherwise, looks good.

Not here. I really need to push the other two bugfixes.

-Aleksey

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