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(ShenandoahSATBBarrier);
  47   SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahKeepAliveBarrier);
  48   SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahWriteBarrier);
  49   SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahReadBarrier);
  50   SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahStoreValEnqueueBarrier);
  51   SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahStoreValReadBarrier);
  52   SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahCASBarrier);
  53   SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahAcmpBarrier);
  54   SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahCloneBarrier);
  55 
  56   // Final configuration checks
  57   // No barriers are required to run.
  58 }
  59 
  60 bool ShenandoahPassiveHeuristics::should_start_normal_gc() const {
  61   // Never do concurrent GCs.
  62   return false;
  63 }
  64 
  65 bool ShenandoahPassiveHeuristics::should_process_references() {
  66   // Always process references, if we can.
  67   return can_process_references();
  68 }
  69 
  70 bool ShenandoahPassiveHeuristics::should_unload_classes() {
  71   // Always unload classes, if we can.
  72   return can_unload_classes();
  73 }
  74 
  75 bool ShenandoahPassiveHeuristics::should_degenerate_cycle() {
  76   // Always fail to Degenerated GC, if enabled
  77   return ShenandoahDegeneratedGC;
  78 }
  79 
  80 void ShenandoahPassiveHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
  81                                                                         RegionData* data, size_t size,
  82                                                                         size_t actual_free) {
  83   assert(ShenandoahDegeneratedGC, "This path is only taken for Degenerated GC");
  84 
  85   // Do not select too large CSet that would overflow the available free space.
  86   // Take at least the entire evacuation reserve, and be free to overflow to free space.
  87   size_t capacity  = ShenandoahHeap::heap()->capacity();
  88   size_t available = MAX2(ShenandoahEvacReserve * capacity / 100, actual_free);
  89   size_t max_cset  = (size_t)(available / ShenandoahEvacWaste);
  90 
  91   log_info(gc, ergo)("CSet Selection. Actual Free: " SIZE_FORMAT "M, Max CSet: " SIZE_FORMAT "M",
  92                      actual_free / M, max_cset / M);
  93 
  94   size_t threshold = ShenandoahHeapRegion::region_size_bytes() * ShenandoahGarbageThreshold / 100;
  95 
  96   size_t live_cset = 0;
  97   for (size_t idx = 0; idx < size; idx++) {
  98     ShenandoahHeapRegion* r = data[idx]._region;
  99     size_t new_cset = live_cset + r->get_live_data_bytes();
 100     if (new_cset < max_cset && r->garbage() > threshold) {
 101       live_cset = new_cset;
 102       cset->add_region(r);
 103     }
 104   }
 105 }
 106 
 107 const char* ShenandoahPassiveHeuristics::name() {
 108   return "passive";
 109 }
 110 
 111 bool ShenandoahPassiveHeuristics::is_diagnostic() {
 112   return true;
 113 }
 114 
 115 bool ShenandoahPassiveHeuristics::is_experimental() {
 116   return false;
 117 }