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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
#include "file_area_freelist.h"
#include <cassert>
namespace vespalib::alloc {
FileAreaFreeList::FileAreaFreeList()
: _free_areas(),
_free_sizes(),
_fences()
{
}
FileAreaFreeList::~FileAreaFreeList()
{
assert(_fences.empty());
}
void
FileAreaFreeList::remove_from_size_set(uint64_t offset, size_t size)
{
auto itr = _free_sizes.find(size);
assert(itr != _free_sizes.end());
auto &offsets = itr->second;
auto erased_count = offsets.erase(offset);
assert(erased_count != 0u);
if (offsets.empty()) {
_free_sizes.erase(itr);
}
}
std::pair<uint64_t, size_t>
FileAreaFreeList::prepare_reuse_area(size_t size)
{
auto itr = _free_sizes.lower_bound(size);
if (itr == _free_sizes.end()) {
return std::make_pair(bad_offset, 0); // No free areas of sufficient size
}
auto old_size = itr->first;
assert(old_size >= size);
auto &offsets = itr->second;
assert(!offsets.empty());
auto oitr = offsets.begin();
auto offset = *oitr;
offsets.erase(oitr);
if (offsets.empty()) {
_free_sizes.erase(itr);
}
// Note: Caller must update _free_areas
return std::make_pair(offset, old_size);
}
uint64_t
FileAreaFreeList::alloc(size_t size)
{
auto reuse_candidate = prepare_reuse_area(size);
auto offset = reuse_candidate.first;
if (offset == bad_offset) {
return bad_offset; // No free areas of sufficient size
}
auto fa_itr = _free_areas.find(offset);
assert(fa_itr != _free_areas.end());
fa_itr = _free_areas.erase(fa_itr);
auto old_size = reuse_candidate.second;
if (old_size > size) {
// Old area beyond what we reuse should still be a free area.
auto ins_res = _free_sizes[old_size - size].insert(offset + size);
assert(ins_res.second);
_free_areas.emplace_hint(fa_itr, offset + size, old_size - size);
}
return offset;
}
void
FileAreaFreeList::free(uint64_t offset, size_t size)
{
auto itr = _free_areas.lower_bound(offset);
if (itr != _free_areas.end() && itr->first <= offset + size) {
assert(itr->first == offset + size);
if (!_fences.contains(offset + size)) {
// Merge with next free area
remove_from_size_set(itr->first, itr->second);
size += itr->second;
itr = _free_areas.erase(itr);
}
}
bool adjusted_prev_area = false;
if (itr != _free_areas.begin()) {
--itr;
if (itr->first + itr->second >= offset) {
assert(itr->first + itr->second == offset);
if (!_fences.contains(offset)) {
// Merge with previous free area
remove_from_size_set(itr->first, itr->second);
offset = itr->first;
size += itr->second;
itr->second = size;
adjusted_prev_area = true;
} else {
++itr;
}
} else {
++itr;
}
}
if (!adjusted_prev_area) {
_free_areas.emplace_hint(itr, offset, size);
}
auto ins_res = _free_sizes[size].insert(offset);
assert(ins_res.second);
}
void
FileAreaFreeList::add_premmapped_area(uint64_t offset, size_t size)
{
auto itr = _free_areas.lower_bound(offset);
if (itr != _free_areas.end()) {
assert(itr->first >= offset + size);
}
auto ins_res = _free_sizes[size].insert(offset);
assert(ins_res.second);
_free_areas.emplace_hint(itr, offset, size);
auto fences_ins_res = _fences.insert(offset);
assert(fences_ins_res.second);
}
void
FileAreaFreeList::remove_premmapped_area(uint64_t offset, size_t size)
{
auto itr = _free_areas.lower_bound(offset);
assert(itr != _free_areas.end());
assert(itr->first == offset);
assert(itr->second == size);
auto sizes_itr = _free_sizes.lower_bound(size);
assert(sizes_itr != _free_sizes.end());
assert(sizes_itr->first == size);
assert(sizes_itr->second.contains(offset));
assert(_fences.contains(offset));
_free_areas.erase(itr);
sizes_itr->second.erase(offset);
if (sizes_itr->second.empty()) {
_free_sizes.erase(sizes_itr);
}
_fences.erase(offset);
}
}
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