1 /*
   2  * Copyright (c) 2018, Red Hat, Inc. All rights reserved.
   3  *
   4  * This code is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License version 2 only, as
   6  * published by the Free Software Foundation.
   7  *
   8  * This code is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  11  * version 2 for more details (a copy is included in the LICENSE file that
  12  * accompanied this code).
  13  *
  14  * You should have received a copy of the GNU General Public License version
  15  * 2 along with this work; if not, write to the Free Software Foundation,
  16  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  17  *
  18  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  19  * or visit www.oracle.com if you need additional information or have any
  20  * questions.
  21  *
  22  */
  23 
  24 #include "precompiled.hpp"
  25 
  26 #include "gc_implementation/shenandoah/heuristics/shenandoahPassiveHeuristics.hpp"
  27 #include "gc_implementation/shenandoah/shenandoahCollectionSet.hpp"
  28 #include "gc_implementation/shenandoah/shenandoahHeap.inline.hpp"
  29 #include "gc_implementation/shenandoah/shenandoahHeapRegion.inline.hpp"
  30 #include "gc_implementation/shenandoah/shenandoahLogging.hpp"
  31 
  32 bool ShenandoahPassiveHeuristics::should_start_gc() const {
  33   // Never do concurrent GCs.
  34   return false;
  35 }
  36 
  37 bool ShenandoahPassiveHeuristics::should_process_references() {
  38   // Always process references, if we can.
  39   return can_process_references();
  40 }
  41 
  42 bool ShenandoahPassiveHeuristics::should_unload_classes() {
  43   // Always unload classes, if we can.
  44   return can_unload_classes();
  45 }
  46 
  47 bool ShenandoahPassiveHeuristics::should_degenerate_cycle() {
  48   // Always fail to Degenerated GC, if enabled
  49   return ShenandoahDegeneratedGC;
  50 }
  51 
  52 void ShenandoahPassiveHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
  53                                                                         RegionData* data, size_t size,
  54                                                                         size_t actual_free) {
  55   assert(ShenandoahDegeneratedGC, "This path is only taken for Degenerated GC");
  56 
  57   // Do not select too large CSet that would overflow the available free space.
  58   // Take at least the entire evacuation reserve, and be free to overflow to free space.
  59   size_t max_capacity = ShenandoahHeap::heap()->max_capacity();
  60   size_t available = MAX2(max_capacity / 100 * ShenandoahEvacReserve, actual_free);
  61   size_t max_cset  = (size_t)(available / ShenandoahEvacWaste);
  62 
  63   log_info(gc, ergo)("CSet Selection. Actual Free: " SIZE_FORMAT "%s, Max CSet: " SIZE_FORMAT "%s",
  64                      byte_size_in_proper_unit(actual_free), proper_unit_for_byte_size(actual_free),
  65                      byte_size_in_proper_unit(max_cset),    proper_unit_for_byte_size(max_cset));
  66 
  67   size_t threshold = ShenandoahHeapRegion::region_size_bytes() * ShenandoahGarbageThreshold / 100;
  68 
  69   size_t live_cset = 0;
  70   for (size_t idx = 0; idx < size; idx++) {
  71     ShenandoahHeapRegion* r = data[idx]._region;
  72     size_t new_cset = live_cset + r->get_live_data_bytes();
  73     if (new_cset < max_cset && r->garbage() > threshold) {
  74       live_cset = new_cset;
  75       cset->add_region(r);
  76     }
  77   }
  78 }