rev 52675 : 8213890: Implementation of JEP 344: Abortable Mixed Collections for G1
Reviewed-by:
Contributed-by: erik.helin@oracle.com, stefan.johansson@oracle.com

   1 /*
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  24 
  25 #ifndef SHARE_VM_GC_G1_G1INCSETSTATE_HPP
  26 #define SHARE_VM_GC_G1_G1INCSETSTATE_HPP
  27 
  28 #include "gc/g1/g1BiasedArray.hpp"
  29 #include "gc/g1/heapRegion.hpp"
  30 
  31 // Per-region state during garbage collection.
  32 struct InCSetState {
  33  public:
  34   // We use different types to represent the state value. Particularly SPARC puts
  35   // values in structs from "left to right", i.e. MSB to LSB. This results in many
  36   // unnecessary shift operations when loading and storing values of this type.
  37   // This degrades performance significantly (>10%) on that platform.
  38   // Other tested ABIs do not seem to have this problem, and actually tend to
  39   // favor smaller types, so we use the smallest usable type there.
  40 #ifdef SPARC
  41   #define CSETSTATE_FORMAT INTPTR_FORMAT
  42   typedef intptr_t in_cset_state_t;
  43 #else
  44   #define CSETSTATE_FORMAT "%d"
  45   typedef int8_t in_cset_state_t;
  46 #endif
  47  private:
  48   in_cset_state_t _value;
  49  public:
  50   enum {
  51     // Selection of the values were driven to micro-optimize the encoding and
  52     // frequency of the checks.
  53     // The most common check is whether the region is in the collection set or not,
  54     // this encoding allows us to use an > 0 check.
  55     // The positive values are encoded in increasing generation order, which
  56     // makes getting the next generation fast by a simple increment. They are also
  57     // used to index into arrays.
  58     // The negative values are used for objects requiring various special cases,
  59     // for example eager reclamation of humongous objects or optional regions.
  60     Optional     = -2,    // The region is optional
  61     Humongous    = -1,    // The region is humongous
  62     NotInCSet    =  0,    // The region is not in the collection set.
  63     Young        =  1,    // The region is in the collection set and a young region.
  64     Old          =  2,    // The region is in the collection set and an old region.
  65     Num
  66   };
  67 
  68   InCSetState(in_cset_state_t value = NotInCSet) : _value(value) {
  69     assert(is_valid(), "Invalid state %d", _value);
  70   }
  71 
  72   in_cset_state_t value() const        { return _value; }
  73 
  74   void set_old()                       { _value = Old; }
  75 
  76   bool is_in_cset_or_humongous() const { return is_in_cset() || is_humongous(); }
  77   bool is_in_cset() const              { return _value > NotInCSet; }
  78 
  79   bool is_humongous() const            { return _value == Humongous; }
  80   bool is_young() const                { return _value == Young; }
  81   bool is_old() const                  { return _value == Old; }
  82   bool is_optional() const             { return _value == Optional; }
  83 
  84 #ifdef ASSERT
  85   bool is_default() const              { return _value == NotInCSet; }
  86   bool is_valid() const                { return (_value >= Optional) && (_value < Num); }
  87   bool is_valid_gen() const            { return (_value >= Young && _value <= Old); }
  88 #endif
  89 };
  90 
  91 // Instances of this class are used for quick tests on whether a reference points
  92 // into the collection set and into which generation or is a humongous object
  93 //
  94 // Each of the array's elements indicates whether the corresponding region is in
  95 // the collection set and if so in which generation, or a humongous region.
  96 //
  97 // We use this to speed up reference processing during young collection and
  98 // quickly reclaim humongous objects. For the latter, by making a humongous region
  99 // succeed this test, we sort-of add it to the collection set. During the reference
 100 // iteration closures, when we see a humongous region, we then simply mark it as
 101 // referenced, i.e. live.
 102 class G1InCSetStateFastTestBiasedMappedArray : public G1BiasedMappedArray<InCSetState> {
 103  protected:
 104   InCSetState default_value() const { return InCSetState::NotInCSet; }
 105  public:
 106   void set_optional(uintptr_t index) {
 107     assert(get_by_index(index).is_default(),
 108            "State at index " INTPTR_FORMAT " should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value());
 109     set_by_index(index, InCSetState::Optional);
 110   }
 111 
 112   void set_humongous(uintptr_t index) {
 113     assert(get_by_index(index).is_default(),
 114            "State at index " INTPTR_FORMAT " should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value());
 115     set_by_index(index, InCSetState::Humongous);
 116   }
 117 
 118   void clear_humongous(uintptr_t index) {
 119     set_by_index(index, InCSetState::NotInCSet);
 120   }
 121 
 122   void set_in_young(uintptr_t index) {
 123     assert(get_by_index(index).is_default(),
 124            "State at index " INTPTR_FORMAT " should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value());
 125     set_by_index(index, InCSetState::Young);
 126   }
 127 
 128   void set_in_old(uintptr_t index) {
 129     assert(get_by_index(index).is_default(),
 130            "State at index " INTPTR_FORMAT " should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value());
 131     set_by_index(index, InCSetState::Old);
 132   }
 133 
 134   bool is_in_cset_or_humongous(HeapWord* addr) const { return at(addr).is_in_cset_or_humongous(); }
 135   bool is_in_cset(HeapWord* addr) const { return at(addr).is_in_cset(); }
 136   bool is_in_cset(const HeapRegion* hr) const { return get_by_index(hr->hrm_index()).is_in_cset(); }
 137   InCSetState at(HeapWord* addr) const { return get_by_address(addr); }
 138   void clear() { G1BiasedMappedArray<InCSetState>::clear(); }
 139   void clear(const HeapRegion* hr) { return set_by_index(hr->hrm_index(), InCSetState::NotInCSet); }
 140 };
 141 
 142 #endif // SHARE_VM_GC_G1_G1INCSETSTATE_HPP
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