8316299: GenShen: Reduce frequency of expedited GC

Reviewed-by: shade, wkemper

src/hotspot/share/gc/shenandoah/heuristics/shenandoahYoungHeuristics.cpp

@@ -135,8 +135,10 @@ bool ShenandoahYoungHeuristics::should_start_gc() {
   // be done, we start up the young-gen GC threads so they can do some of this old-gen work.  As implemented, promotion
   // gets priority over old-gen marking.
   ShenandoahHeap* heap = ShenandoahHeap::heap();
+
+  size_t promo_expedite_threshold = (heap->young_generation()->max_capacity() * ShenandoahEvacReserve) / 512;
   size_t promo_potential = heap->get_promotion_potential();
-  if (promo_potential > 0) {
+  if (promo_potential > promo_expedite_threshold) {
     // Detect unsigned arithmetic underflow
     assert(promo_potential < heap->capacity(), "Sanity");
     log_info(gc)("Trigger (%s): expedite promotion of " SIZE_FORMAT "%s",
@@ -146,17 +148,6 @@ bool ShenandoahYoungHeuristics::should_start_gc() {
     return true;
   }
 
-  size_t promo_in_place_potential = heap->get_promotion_in_place_potential();
-  if (promo_in_place_potential > 0) {
-    // Detect unsigned arithmetic underflow
-    assert(promo_in_place_potential < heap->capacity(), "Sanity");
-    log_info(gc)("Trigger (%s): expedite promotion in place of " SIZE_FORMAT "%s",
-                 _space_info->name(),
-                 byte_size_in_proper_unit(promo_in_place_potential),
-                 proper_unit_for_byte_size(promo_in_place_potential));
-    return true;
-  }
-
   ShenandoahOldHeuristics* old_heuristics = heap->old_heuristics();
   size_t mixed_candidates = old_heuristics->unprocessed_old_collection_candidates();
   if (mixed_candidates > 0) {

src/hotspot/share/gc/shenandoah/shenandoahFullGC.cpp

@@ -1556,7 +1556,6 @@ void ShenandoahFullGC::phase5_epilog() {
 
     // In case this Full GC resulted from degeneration, clear the tally on anticipated promotion.
     heap->clear_promotion_potential();
-    heap->clear_promotion_in_place_potential();
 
     if (heap->mode()->is_generational()) {
       // Invoke this in case we are able to transfer memory from OLD to YOUNG.

src/hotspot/share/gc/shenandoah/shenandoahGeneration.cpp

@@ -537,9 +537,7 @@ size_t ShenandoahGeneration::select_aged_regions(size_t old_available, size_t nu
 
   size_t old_consumed = 0;
   size_t promo_potential = 0;
-  size_t anticipated_promote_in_place_live = 0;
 
-  heap->clear_promotion_in_place_potential();
   heap->clear_promotion_potential();
   size_t candidates = 0;
   size_t candidates_live = 0;
@@ -626,7 +624,6 @@ size_t ShenandoahGeneration::select_aged_regions(size_t old_available, size_t nu
         }
         else {
           anticipated_promote_in_place_regions++;
-          anticipated_promote_in_place_live += r->get_live_data_bytes();
         }
       }
     }
@@ -662,7 +659,6 @@ size_t ShenandoahGeneration::select_aged_regions(size_t old_available, size_t nu
   }
   heap->set_pad_for_promote_in_place(promote_in_place_pad);
   heap->set_promotion_potential(promo_potential);
-  heap->set_promotion_in_place_potential(anticipated_promote_in_place_live);
   return old_consumed;
 }
 

src/hotspot/share/gc/shenandoah/shenandoahGeneration.hpp

@@ -85,12 +85,6 @@ class ShenandoahGeneration : public CHeapObj<mtGC>, public ShenandoahSpaceInfo {
   // at or above tenure age and which contain more than ShenandoahOldGarbageThreshold
   // amounts of garbage.
   //
-  // A side effect performed by this function is to tally up the number of regions and
-  // the number of live bytes that we plan to promote-in-place during the current GC cycle.
-  // This information, which is stored with an invocation of heap->set_promotion_in_place_potential(),
-  // feeds into subsequent decisions about when to trigger the next GC and may identify
-  // special work to be done during this GC cycle if we choose to abbreviate it.
-  //
   // Returns bytes of old-gen memory consumed by selected aged regions
   size_t select_aged_regions(size_t old_available,
                              size_t num_regions, bool

src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp

@@ -586,7 +586,6 @@ ShenandoahHeap::ShenandoahHeap(ShenandoahCollectorPolicy* policy) :
   _prepare_for_old_mark(false),
   _initial_size(0),
   _promotion_potential(0),
-  _promotion_in_place_potential(0),
   _committed(0),
   _max_workers(MAX3(ConcGCThreads, ParallelGCThreads, 1U)),
   _workers(nullptr),

src/hotspot/share/gc/shenandoah/shenandoahHeap.hpp

@@ -226,7 +226,6 @@ class ShenandoahHeap : public CollectedHeap {
            size_t _initial_size;
            size_t _minimum_size;
            size_t _promotion_potential;
-           size_t _promotion_in_place_potential;
            size_t _pad_for_promote_in_place;    // bytes of filler
            size_t _promotable_humongous_regions;
            size_t _promotable_humongous_usage;
@@ -453,10 +452,6 @@ class ShenandoahHeap : public CollectedHeap {
   inline void set_promotion_potential(size_t val) { _promotion_potential = val; };
   inline size_t get_promotion_potential() { return _promotion_potential; };
 
-  inline void clear_promotion_in_place_potential() { _promotion_in_place_potential = 0; };
-  inline void set_promotion_in_place_potential(size_t val) { _promotion_in_place_potential = val; };
-  inline size_t get_promotion_in_place_potential() { return _promotion_in_place_potential; };
-
   inline void set_pad_for_promote_in_place(size_t pad) { _pad_for_promote_in_place = pad; }
   inline size_t get_pad_for_promote_in_place() { return _pad_for_promote_in_place; }