tests/test_gc23.cc

   1 //////////////////////////////////////////////////////////////////////////////
   2 //  This program tests the garbage collector classes.
   3 //  We'll allocate a long linked list in the collectable heap, then invoke
   4 //  garbage collection a few times.
   5 //
   6 //  Note: In your application you'll only have to include <AD/gc/gcobject.h>.
   7 //  In this case we'll have to import some other implementation dependent
   8 //  information since we'll have do some poking around with the heap.
   9 //////////////////////////////////////////////////////////////////////////////
  10
  11 #include <assert.h>
  12 #include <iostream.h>
  13 #include <AD/gc/bgc.h>
  14 #include <AD/gc/gcobject.h>
  15 #include <AD/gc/gcheaps.h>
  16
  17 #define LENGTH (256)
  18 #define UNIT   (16 * 64)
  19 #define HEAP_POINTERS 100
  20 #define TRIALS 100
  21
  22 //////////////////////////////////////////////////////////////////////////////
  23 //  The list class defined below is made a garbage collectable class by
  24 //  deriving from GCObject and adding a tracing method ``trace.''
  25 //////////////////////////////////////////////////////////////////////////////
  26 class LIST : public GCObject {
  27 public:
  28    char   c;      // some position dependent   storage
  29    int    x[20];  // some other position independent junk
  30    LIST * next;   // the link
  31
  32    // The constructor
  33    LIST(LIST * n, char c1) : next(n), c(c1)
  34       { for (int i = 0; i < 20; i++) x[i] = i; }
  35
  36 private:
  37    // The tracing method.
  38    void trace(GC * gc) { next = (LIST *)gc->trace(next); }
  39 };
  40
  41 //////////////////////////////////////////////////////////////////////////////
  42 //  Method to print a list, currently unused.
  43 //////////////////////////////////////////////////////////////////////////////
  44 void print(LIST * x)
  45 {  if (x) { cout << x->c; print(x->next); }
  46 }
  47
  48 //////////////////////////////////////////////////////////////////////////////
  49 //  This method checks that a list is well and okay.
  50 //////////////////////////////////////////////////////////////////////////////
  51 void verify (LIST * x)
  52 {  int count = 0;
  53    // cout << "Verifying list\n" << flush;
  54    for ( ; x; x = x->next, count++) {
  55       //
  56       // Make sure that it lies within the collectable heap.
  57       //
  58       assert (HM::is_mapped(x) && HM::page_gc(x) == bgc.gc_id());
  59       assert (HM::get_object_map().is_marked(x));
  60
  61       // Check its contents
  62       for (int i = 0; i < 20; i++)
  63          assert (x->x[i] == i);
  64       assert (x->c == (LENGTH - count - 1) / UNIT + 'a');
  65    }
  66
  67    // Make sure that it has the right length.
  68    assert (count == LENGTH);
  69 }
  70
  71
  72 void do_some_stuff(int trial)
  73 {
  74    LIST ** heap = new LIST * [HEAP_POINTERS];
  75
  76    // Allocate a list
  77    int j;
  78    for (j = 0; j < HEAP_POINTERS; j++) {
  79       LIST * x  = 0;
  80       for (int i = 0; i < LENGTH; i++) {
  81          x = new LIST (x,i / UNIT + 'a');
  82          // The following line generates some garbage.
  83          new LIST (x, i / UNIT + 'a');
  84       }
  85       heap[j] = x;
  86    }
  87
  88    cout << "List allocated\n";
  89    // cout << "Address of heap[] = " << (void*)heap << '\n';
  90    // GCHeapManager::print_report(cout);
  91    for (j = 0; j < HEAP_POINTERS; j++) {
  92       // cout << "[" << j << "]" << flush;
  93       verify(heap[j]);
  94    }
  95
  96    GC::get_default_gc().collect();
  97    for (j = 0; j < HEAP_POINTERS; j++) {
  98       // cout << "[" << j << "]" << flush;
  99       verify(heap[j]);
 100    }
 101    GC::get_default_gc().collect();
 102
 103    for (j = 0; j < HEAP_POINTERS; j++) {
 104       // cout << "[" << j << "]" << flush;
 105       verify(heap[j]);
 106    }
 107    for (j = 0; j < HEAP_POINTERS; j++) {
 108       heap[j] = 0;
 109    }
 110    cout << "Trial = " << trial << " List is okay\n" << flush;
 111    GC::get_default_gc().collect();
 112    delete [] heap;
 113 }
 114
 115 int main()
 116 {
 117    GC::get_default_gc().set_verbosity(
 118       GC::gc_print_debugging_info | GC::get_default_gc().verbosity());
 119    GC::get_default_gc().set_initial_heap_size(1024*1024);
 120    GC::Statistics stats = GC::get_default_gc().statistics();
 121    cout << "Algorithm:        " << stats.algorithm << '\n'
 122         << "Version:          " << stats.version << '\n';
 123
 124    for (int i = 0; i < TRIALS; i++)
 125       do_some_stuff(i);
 126
 127    GC::get_default_gc().collect();
 128
 129    stats = GC::get_default_gc().statistics();
 130    size_t memory_allocated = sizeof(LIST) * LENGTH * 2 * HEAP_POINTERS;
 131
 132    cout << "\n"
 133            "Memory allocated: " << memory_allocated << '\n'
 134         << "Final heap size:  "
 135             << stats.bytes_managed + GCHeapManager::bytes_free() << '\n'
 136         << "Bytes retained:   " << stats.bytes_used << '\n'
 137         << "Retention rate:   "
 138            << (stats.bytes_used * 100 / memory_allocated) << "%\n"
 139         << "\n"
 140            "If you don't see a crash by now then it's probably ok :-)\n"
 141            "Ideally, the heap should be completely reclaimed at this\n"
 142            "point, but since the collector is conservative, retention\n"
 143            "may occur.\n"
 144            "\n"
 145            "Actually this test is bit unfair, since we are allocating\n"
 146            "a long linked list, a strongly connected data structure, and if\n"
 147            "any one part of the list is incorrectly promoted then a large\n"
 148            "portion of the storage will be retained.\n"
 149            "\n"
 150            "Happy GC!\n";
 151    return 0;
 152 }