vm/free_list.cpp

   1 #include "master.hpp"
   2
   3 namespace factor {
   4
   5 void free_list::clear_free_list() {
   6   for (cell i = 0; i < free_list_count; i++)
   7     small_blocks[i].clear();
   8   large_blocks.clear();
   9   free_block_count = 0;
  10   free_space = 0;
  11 }
  12
  13 void free_list::initial_free_list(cell start, cell end, cell occupied) {
  14   clear_free_list();
  15   if (occupied != end - start) {
  16     free_heap_block* last_block = (free_heap_block*)(start + occupied);
  17     last_block->make_free(end - (cell)last_block);
  18     add_to_free_list(last_block);
  19   }
  20 }
  21
  22 void free_list::add_to_free_list(free_heap_block* block) {
  23   cell size = block->size();
  24
  25   free_block_count++;
  26   free_space += size;
  27
  28   if (size < free_list_count * data_alignment)
  29     small_blocks[size / data_alignment].push_back(block);
  30   else
  31     large_blocks.insert(block);
  32 }
  33
  34 free_heap_block* free_list::find_free_block(cell size) {
  35   // Check small free lists
  36   cell bucket = size / data_alignment;
  37   if (bucket < free_list_count) {
  38     std::vector<free_heap_block*>& blocks = small_blocks[bucket];
  39     if (blocks.size() == 0) {
  40       // Round up to a multiple of 'size'
  41       cell large_block_size = ((allocation_page_size + size - 1) / size) * size;
  42
  43       // Allocate a block this big
  44       free_heap_block* large_block = find_free_block(large_block_size);
  45       if (!large_block)
  46         return NULL;
  47
  48       large_block = split_free_block(large_block, large_block_size);
  49
  50       // Split it up into pieces and add each piece back to the free list
  51       for (cell offset = 0; offset < large_block_size; offset += size) {
  52         free_heap_block* small_block = large_block;
  53         large_block = (free_heap_block*)((cell)large_block + size);
  54         small_block->make_free(size);
  55         add_to_free_list(small_block);
  56       }
  57     }
  58
  59     free_heap_block* block = blocks.back();
  60     blocks.pop_back();
  61
  62     free_block_count--;
  63     free_space -= block->size();
  64
  65     return block;
  66   } else {
  67     // Check large free list
  68     free_heap_block key;
  69     key.make_free(size);
  70     large_block_set::iterator iter = large_blocks.lower_bound(&key);
  71     large_block_set::iterator end = large_blocks.end();
  72
  73     if (iter != end) {
  74       free_heap_block* block = *iter;
  75       large_blocks.erase(iter);
  76
  77       free_block_count--;
  78       free_space -= block->size();
  79
  80       return block;
  81     }
  82
  83     return NULL;
  84   }
  85 }
  86
  87 free_heap_block* free_list::split_free_block(free_heap_block* block,
  88                                              cell size) {
  89   if (block->size() != size) {
  90     // split the block in two
  91     free_heap_block* split = (free_heap_block*)((cell)block + size);
  92     split->make_free(block->size() - size);
  93     block->make_free(size);
  94     add_to_free_list(split);
  95   }
  96
  97   return block;
  98 }
  99
 100 bool free_list::can_allot_p(cell size) {
 101   return largest_free_block() >= std::max(size, allocation_page_size);
 102 }
 103
 104 cell free_list::largest_free_block() {
 105   if (large_blocks.size()) {
 106     large_block_set::reverse_iterator last = large_blocks.rbegin();
 107     return (*last)->size();
 108   } else {
 109     for (int i = free_list_count - 1; i >= 0; i--) {
 110       if (small_blocks[i].size())
 111         return small_blocks[i].back()->size();
 112     }
 113
 114     return 0;
 115   }
 116 }
 117
 118 }