RFR: Off-by-one error in degen progress calculation

[Aleksey Shipilev]

Freeing up one region is enough, but it is not captured, because we have off-by-one error here:

diff -r cc8a1bd74e70 src/hotspot/share/gc/shenandoah/shenandoahMetrics.cpp
--- a/src/hotspot/share/gc/shenandoah/shenandoahMetrics.cpp     Thu Aug 30 20:18:48 2018 +0200
+++ b/src/hotspot/share/gc/shenandoah/shenandoahMetrics.cpp     Thu Aug 30 20:19:23 2018 +0200
@@ -146,11 +146,11 @@
   }

   // Freed up enough? Good! Declare victory.
   size_t progress_actual   = (_used_before > _used_after) ? _used_before - _used_after : 0;
   size_t progress_expected = ShenandoahHeapRegion::region_size_bytes();
-  if (progress_actual > progress_expected) {
+  if (progress_actual >= progress_expected) {
     return true;
   }
   log_info(gc,ergo)("Not enough progress (" SIZE_FORMAT "M, need " SIZE_FORMAT "M) after %s",
                     progress_actual / M, progress_expected / M, label);


Testing: tier1_gc_shenandoah, eyeballing heavy degen workloads

Thanks,
-Aleksey