vm: use STL in free list, makes finding largest contiguous free block slightly faster

db4
Slava Pestov 2009-10-27 18:22:08 -05:00
parent 028a7be4d6
commit a7b55e7068
2 changed files with 58 additions and 60 deletions

View File

@ -5,7 +5,11 @@ namespace factor
void free_list::clear_free_list()
{
memset(this,0,sizeof(free_list));
for(cell i = 0; i < free_list_count; i++)
small_blocks[i].clear();
large_blocks.clear();
free_block_count = 0;
free_space = 0;
}
void free_list::initial_free_list(cell start, cell end, cell occupied)
@ -27,59 +31,40 @@ void free_list::add_to_free_list(free_heap_block *block)
free_space += size;
if(size < free_list_count * block_granularity)
{
int index = size / block_granularity;
block->next_free = small_blocks[index];
small_blocks[index] = block;
}
small_blocks[size / block_granularity].push_back(block);
else
{
block->next_free = large_blocks;
large_blocks = block;
}
large_blocks.insert(block);
}
free_heap_block *free_list::find_free_block(cell size)
{
cell attempt = size;
while(attempt < free_list_count * block_granularity)
/* Check small free lists */
for(cell i = size / block_granularity; i < free_list_count; i++)
{
int index = attempt / block_granularity;
free_heap_block *block = small_blocks[index];
if(block)
std::vector<free_heap_block *> &blocks = small_blocks[i];
if(blocks.size())
{
small_blocks[index] = block->next_free;
free_block_count--;
free_space -= block->size();
free_heap_block *block = blocks.back();
blocks.pop_back();
return block;
}
attempt++;
}
free_heap_block *prev = NULL;
free_heap_block *block = large_blocks;
/* Check large free lists */
free_heap_block key;
key.make_free(size);
large_block_set::iterator iter = large_blocks.lower_bound(&key);
large_block_set::iterator end = large_blocks.end();
while(block)
if(iter != end)
{
if(block->size() >= size)
{
if(prev)
prev->next_free = block->next_free;
else
large_blocks = block->next_free;
free_heap_block *block = *iter;
large_blocks.erase(iter);
free_block_count--;
free_space -= block->size();
free_block_count--;
free_space -= block->size();
return block;
}
prev = block;
block = block->next_free;
return block;
}
return NULL;
@ -92,7 +77,6 @@ free_heap_block *free_list::split_free_block(free_heap_block *block, cell size)
/* split the block in two */
free_heap_block *split = (free_heap_block *)((cell)block + size);
split->make_free(block->size() - size);
split->next_free = block->next_free;
block->make_free(size);
add_to_free_list(split);
}
@ -102,20 +86,19 @@ free_heap_block *free_list::split_free_block(free_heap_block *block, cell size)
bool free_list::can_allot_p(cell size)
{
cell attempt = size;
while(attempt < free_list_count * block_granularity)
/* Check small free lists */
for(cell i = size / block_granularity; i < free_list_count; i++)
{
int index = attempt / block_granularity;
if(small_blocks[index]) return true;
attempt++;
if(small_blocks[i].size()) return true;
}
free_heap_block *block = large_blocks;
while(block)
/* Check large free lists */
large_block_set::const_iterator iter = large_blocks.begin();
large_block_set::const_iterator end = large_blocks.end();
for(; iter != end; iter++)
{
if(block->size() >= size) return true;
block = block->next_free;
if((*iter)->size() >= size) return true;
}
return false;
@ -123,16 +106,23 @@ bool free_list::can_allot_p(cell size)
cell free_list::largest_free_block()
{
cell largest = 0;
free_heap_block *scan = large_blocks;
while(scan)
if(large_blocks.size())
{
largest = std::max(largest,scan->size());
scan = scan->next_free;
large_block_set::iterator end = large_blocks.end();
free_heap_block *block = *end;
large_blocks.erase(end);
return block->size();
}
else
{
for(int i = free_list_count - 1; i >= 0; i--)
{
if(small_blocks[i].size())
return small_blocks[i].back()->size();
}
return largest;
return 0;
}
}
}

View File

@ -6,7 +6,6 @@ static const cell free_list_count = 32;
struct free_heap_block
{
cell header;
free_heap_block *next_free;
bool free_p() const
{
@ -24,9 +23,18 @@ struct free_heap_block
}
};
struct block_size_compare {
bool operator()(free_heap_block *a, free_heap_block *b)
{
return a->size() < b->size();
}
};
typedef std::multiset<free_heap_block *, block_size_compare> large_block_set;
struct free_list {
free_heap_block *small_blocks[free_list_count];
free_heap_block *large_blocks;
std::vector<free_heap_block *> small_blocks[free_list_count];
large_block_set large_blocks;
cell free_block_count;
cell free_space;