void Slab_cache::free (void *ptr)
{
Lock_guard <Spinlock> guard (lock);
Slab *slab = reinterpret_cast<Slab *>(reinterpret_cast<mword>(ptr) & ~PAGE_MASK);
bool was_full = slab->full();
slab->free (ptr); // Deallocate from slab
if (EXPECT_FALSE (was_full)) {
// There are full slabs in front of us and we're partial; requeue
if (slab->prev && slab->prev->full()) {
// Dequeue
slab->prev->next = slab->next;
if (slab->next)
slab->next->prev = slab->prev;
// Enqueue after curr
if (curr) {
slab->prev = curr;
slab->next = curr->next;
curr->next = curr->next->prev = slab;
}
// Enqueue as head
else {
slab->prev = nullptr;
slab->next = head;
head = head->prev = slab;
}
}
curr = slab;
} else if (EXPECT_FALSE (slab->empty())) {
// There are partial slabs in front of us and we're empty; requeue
if (slab->prev && !slab->prev->empty()) {
// Make partial slab in front of us current if we were current
if (slab == curr)
curr = slab->prev;
// Dequeue
slab->prev->next = slab->next;
if (slab->next)
slab->next->prev = slab->prev;
// Enqueue as head
slab->prev = nullptr;
slab->next = head;
head = head->prev = slab;
}
}
}
PUBLIC
void
Slab_cache::free(void *cache_entry) // return initialized member to cache
{
Slab *to_free = 0;
{
auto guard = lock_guard(lock);
Slab *s = reinterpret_cast<Slab*>
((reinterpret_cast<unsigned long>(cache_entry) & ~(_slab_size - 1)) + _slab_size - sizeof(Slab));
bool was_full = s->is_full();
s->free(cache_entry);
if (was_full)
{
cxx::H_list<Slab>::remove(s);
_partial.add(s);
}
else if (s->is_empty())
{
cxx::H_list<Slab>::remove(s);
if (_num_empty < 2)
{
_empty.add(s);
++_num_empty;
}
else
to_free = s;
}
else
{
// We weren't either full or empty; we already had free
// elements. This changes nothing in the queue, and there
// already must have been a _first_available_slab.
}
}
if (to_free)
{
to_free->~Slab();
block_free(reinterpret_cast<char *>(to_free + 1) - _slab_size, _slab_size);
}
}