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      1 /*
      2  * Copyright (C) 2012 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef ART_RUNTIME_GC_COLLECTOR_GARBAGE_COLLECTOR_H_
     18 #define ART_RUNTIME_GC_COLLECTOR_GARBAGE_COLLECTOR_H_
     19 
     20 #include <stdint.h>
     21 #include <vector>
     22 
     23 #include "base/histogram.h"
     24 #include "base/mutex.h"
     25 #include "base/timing_logger.h"
     26 #include "gc/collector_type.h"
     27 #include "gc/gc_cause.h"
     28 #include "gc_root.h"
     29 #include "gc_type.h"
     30 #include "object_callbacks.h"
     31 
     32 namespace art {
     33 
     34 namespace mirror {
     35 class Class;
     36 class Object;
     37 class Reference;
     38 }  // namespace mirror
     39 
     40 namespace gc {
     41 
     42 class Heap;
     43 
     44 namespace collector {
     45 
     46 struct ObjectBytePair {
     47   explicit ObjectBytePair(uint64_t num_objects = 0, int64_t num_bytes = 0)
     48       : objects(num_objects), bytes(num_bytes) {}
     49   void Add(const ObjectBytePair& other) {
     50     objects += other.objects;
     51     bytes += other.bytes;
     52   }
     53   // Number of objects which were freed.
     54   uint64_t objects;
     55   // Freed bytes are signed since the GC can free negative bytes if it promotes objects to a space
     56   // which has a larger allocation size.
     57   int64_t bytes;
     58 };
     59 
     60 // A information related single garbage collector iteration. Since we only ever have one GC running
     61 // at any given time, we can have a single iteration info.
     62 class Iteration {
     63  public:
     64   Iteration();
     65   // Returns how long the mutators were paused in nanoseconds.
     66   const std::vector<uint64_t>& GetPauseTimes() const {
     67     return pause_times_;
     68   }
     69   TimingLogger* GetTimings() {
     70     return &timings_;
     71   }
     72   // Returns how long the GC took to complete in nanoseconds.
     73   uint64_t GetDurationNs() const {
     74     return duration_ns_;
     75   }
     76   int64_t GetFreedBytes() const {
     77     return freed_.bytes;
     78   }
     79   int64_t GetFreedLargeObjectBytes() const {
     80     return freed_los_.bytes;
     81   }
     82   uint64_t GetFreedObjects() const {
     83     return freed_.objects;
     84   }
     85   uint64_t GetFreedLargeObjects() const {
     86     return freed_los_.objects;
     87   }
     88   uint64_t GetFreedRevokeBytes() const {
     89     return freed_bytes_revoke_;
     90   }
     91   void SetFreedRevoke(uint64_t freed) {
     92     freed_bytes_revoke_ = freed;
     93   }
     94   void Reset(GcCause gc_cause, bool clear_soft_references);
     95   // Returns the estimated throughput of the iteration.
     96   uint64_t GetEstimatedThroughput() const;
     97   bool GetClearSoftReferences() const {
     98     return clear_soft_references_;
     99   }
    100   void SetClearSoftReferences(bool clear_soft_references) {
    101     clear_soft_references_ = clear_soft_references;
    102   }
    103   GcCause GetGcCause() const {
    104     return gc_cause_;
    105   }
    106 
    107  private:
    108   void SetDurationNs(uint64_t duration) {
    109     duration_ns_ = duration;
    110   }
    111 
    112   GcCause gc_cause_;
    113   bool clear_soft_references_;
    114   uint64_t duration_ns_;
    115   TimingLogger timings_;
    116   ObjectBytePair freed_;
    117   ObjectBytePair freed_los_;
    118   uint64_t freed_bytes_revoke_;  // see Heap::num_bytes_freed_revoke_.
    119   std::vector<uint64_t> pause_times_;
    120 
    121   friend class GarbageCollector;
    122   DISALLOW_COPY_AND_ASSIGN(Iteration);
    123 };
    124 
    125 class GarbageCollector : public RootVisitor, public IsMarkedVisitor, public MarkObjectVisitor {
    126  public:
    127   class SCOPED_LOCKABLE ScopedPause {
    128    public:
    129     explicit ScopedPause(GarbageCollector* collector, bool with_reporting = true)
    130         EXCLUSIVE_LOCK_FUNCTION(Locks::mutator_lock_);
    131     ~ScopedPause() UNLOCK_FUNCTION();
    132 
    133    private:
    134     const uint64_t start_time_;
    135     GarbageCollector* const collector_;
    136     bool with_reporting_;
    137   };
    138 
    139   GarbageCollector(Heap* heap, const std::string& name);
    140   virtual ~GarbageCollector() { }
    141   const char* GetName() const {
    142     return name_.c_str();
    143   }
    144   virtual GcType GetGcType() const = 0;
    145   virtual CollectorType GetCollectorType() const = 0;
    146   // Run the garbage collector.
    147   void Run(GcCause gc_cause, bool clear_soft_references) REQUIRES(!pause_histogram_lock_);
    148   Heap* GetHeap() const {
    149     return heap_;
    150   }
    151   void RegisterPause(uint64_t nano_length);
    152   const CumulativeLogger& GetCumulativeTimings() const {
    153     return cumulative_timings_;
    154   }
    155   void ResetCumulativeStatistics() REQUIRES(!pause_histogram_lock_);
    156   // Swap the live and mark bitmaps of spaces that are active for the collector. For partial GC,
    157   // this is the allocation space, for full GC then we swap the zygote bitmaps too.
    158   void SwapBitmaps()
    159       REQUIRES(Locks::heap_bitmap_lock_)
    160       REQUIRES_SHARED(Locks::mutator_lock_);
    161   uint64_t GetTotalPausedTimeNs() REQUIRES(!pause_histogram_lock_);
    162   int64_t GetTotalFreedBytes() const {
    163     return total_freed_bytes_;
    164   }
    165   uint64_t GetTotalFreedObjects() const {
    166     return total_freed_objects_;
    167   }
    168   // Reset the cumulative timings and pause histogram.
    169   void ResetMeasurements() REQUIRES(!pause_histogram_lock_);
    170   // Returns the estimated throughput in bytes / second.
    171   uint64_t GetEstimatedMeanThroughput() const;
    172   // Returns how many GC iterations have been run.
    173   size_t NumberOfIterations() const {
    174     return GetCumulativeTimings().GetIterations();
    175   }
    176   // Returns the current GC iteration and assocated info.
    177   Iteration* GetCurrentIteration();
    178   const Iteration* GetCurrentIteration() const;
    179   TimingLogger* GetTimings() {
    180     return &GetCurrentIteration()->timings_;
    181   }
    182   // Record a free of normal objects.
    183   void RecordFree(const ObjectBytePair& freed);
    184   // Record a free of large objects.
    185   void RecordFreeLOS(const ObjectBytePair& freed);
    186   virtual void DumpPerformanceInfo(std::ostream& os) REQUIRES(!pause_histogram_lock_);
    187 
    188   // Helper functions for querying if objects are marked. These are used for processing references,
    189   // and will be used for reading system weaks while the GC is running.
    190   virtual mirror::Object* IsMarked(mirror::Object* obj)
    191       REQUIRES_SHARED(Locks::mutator_lock_) = 0;
    192   // Returns true if the given heap reference is null or is already marked. If it's already marked,
    193   // update the reference (uses a CAS if do_atomic_update is true. Otherwise, returns false.
    194   virtual bool IsNullOrMarkedHeapReference(mirror::HeapReference<mirror::Object>* obj,
    195                                            bool do_atomic_update)
    196       REQUIRES_SHARED(Locks::mutator_lock_) = 0;
    197   // Used by reference processor.
    198   virtual void ProcessMarkStack() REQUIRES_SHARED(Locks::mutator_lock_) = 0;
    199   // Force mark an object.
    200   virtual mirror::Object* MarkObject(mirror::Object* obj)
    201       REQUIRES_SHARED(Locks::mutator_lock_) = 0;
    202   virtual void MarkHeapReference(mirror::HeapReference<mirror::Object>* obj,
    203                                  bool do_atomic_update)
    204       REQUIRES_SHARED(Locks::mutator_lock_) = 0;
    205   virtual void DelayReferenceReferent(ObjPtr<mirror::Class> klass,
    206                                       ObjPtr<mirror::Reference> reference)
    207       REQUIRES_SHARED(Locks::mutator_lock_) = 0;
    208 
    209   bool IsTransactionActive() const {
    210     return is_transaction_active_;
    211   }
    212 
    213  protected:
    214   // Run all of the GC phases.
    215   virtual void RunPhases() = 0;
    216   // Revoke all the thread-local buffers.
    217   virtual void RevokeAllThreadLocalBuffers() = 0;
    218 
    219   static constexpr size_t kPauseBucketSize = 500;
    220   static constexpr size_t kPauseBucketCount = 32;
    221 
    222   Heap* const heap_;
    223   std::string name_;
    224   // Cumulative statistics.
    225   Histogram<uint64_t> pause_histogram_ GUARDED_BY(pause_histogram_lock_);
    226   uint64_t total_time_ns_;
    227   uint64_t total_freed_objects_;
    228   int64_t total_freed_bytes_;
    229   CumulativeLogger cumulative_timings_;
    230   mutable Mutex pause_histogram_lock_ DEFAULT_MUTEX_ACQUIRED_AFTER;
    231   bool is_transaction_active_;
    232 
    233  private:
    234   DISALLOW_IMPLICIT_CONSTRUCTORS(GarbageCollector);
    235 };
    236 
    237 }  // namespace collector
    238 }  // namespace gc
    239 }  // namespace art
    240 
    241 #endif  // ART_RUNTIME_GC_COLLECTOR_GARBAGE_COLLECTOR_H_
    242