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/shenandoah/heuristics/shenandoahPassiveHeuristics.hpp"
  27 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
  28 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
  29 #include "logging/log.hpp"
  30 #include "logging/logTag.hpp"
  31 
  32 ShenandoahPassiveHeuristics::ShenandoahPassiveHeuristics() : ShenandoahHeuristics() {
  33   // Do not allow concurrent cycles.
  34   FLAG_SET_DEFAULT(ExplicitGCInvokesConcurrent, false);
  35   FLAG_SET_DEFAULT(ShenandoahImplicitGCInvokesConcurrent, false);
  36 
  37   // Passive runs with max speed, reacts on allocation failure.
  38   FLAG_SET_DEFAULT(ShenandoahPacing, false);
  39 
  40   // No need for evacuation reserve with Full GC, only for Degenerated GC.
  41   if (!ShenandoahDegeneratedGC) {
  42     SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahEvacReserve, 0);
  43   }
  44 
  45   // Disable known barriers by default.
  46   SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahLoadRefBarrier);
  47   SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahSATBBarrier);
  48   SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahKeepAliveBarrier);
  49   SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahStoreValEnqueueBarrier);
  50   SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahCASBarrier);
  51   SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahCloneBarrier);
  52 
  53   // Final configuration checks
  54   // No barriers are required to run.
  55 }
  56 
  57 bool ShenandoahPassiveHeuristics::should_start_normal_gc() const {
  58   // Never do concurrent GCs.
  59   return false;
  60 }
  61 
  62 bool ShenandoahPassiveHeuristics::should_process_references() {
  63   // Always process references, if we can.
  64   return can_process_references();
  65 }
  66 
  67 bool ShenandoahPassiveHeuristics::should_unload_classes() {
  68   // Always unload classes, if we can.
  69   return can_unload_classes();
  70 }
  71 
  72 bool ShenandoahPassiveHeuristics::should_degenerate_cycle() {
  73   // Always fail to Degenerated GC, if enabled
  74   return ShenandoahDegeneratedGC;
  75 }
  76 
  77 void ShenandoahPassiveHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
  78                                                                         RegionData* data, size_t size,
  79                                                                         size_t actual_free) {
  80   assert(ShenandoahDegeneratedGC, "This path is only taken for Degenerated GC");
  81 
  82   // Do not select too large CSet that would overflow the available free space.
  83   // Take at least the entire evacuation reserve, and be free to overflow to free space.
  84   size_t capacity  = ShenandoahHeap::heap()->capacity();
  85   size_t available = MAX2(ShenandoahEvacReserve * capacity / 100, actual_free);
  86   size_t max_cset  = (size_t)(available / ShenandoahEvacWaste);
  87 
  88   log_info(gc, ergo)("CSet Selection. Actual Free: " SIZE_FORMAT "M, Max CSet: " SIZE_FORMAT "M",
  89                      actual_free / M, max_cset / M);
  90 
  91   size_t threshold = ShenandoahHeapRegion::region_size_bytes() * ShenandoahGarbageThreshold / 100;
  92 
  93   size_t live_cset = 0;
  94   for (size_t idx = 0; idx < size; idx++) {
  95     ShenandoahHeapRegion* r = data[idx]._region;
  96     size_t new_cset = live_cset + r->get_live_data_bytes();
  97     if (new_cset < max_cset && r->garbage() > threshold) {
  98       live_cset = new_cset;
  99       cset->add_region(r);
 100     }
 101   }
 102 }
 103 
 104 const char* ShenandoahPassiveHeuristics::name() {
 105   return "passive";
 106 }
 107 
 108 bool ShenandoahPassiveHeuristics::is_diagnostic() {
 109   return true;
 110 }
 111 
 112 bool ShenandoahPassiveHeuristics::is_experimental() {
 113   return false;
 114 }
--- EOF ---