mirror of https://github.com/OpenTTD/OpenTTD.git
Change: Improve performance of finding free pool slots. (#12055)
Add a bitmap of used pool slots which allows finding a free pool slot without having to check if each index is already used or not. Loosely based on a JGRPP patch.
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@ -11,6 +11,7 @@
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#define POOL_FUNC_HPP
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#include "alloc_func.hpp"
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#include "bitmath_func.hpp"
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#include "mem_func.hpp"
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#include "pool_type.hpp"
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#include "../error_func.h"
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@ -60,6 +61,16 @@ DEFINE_POOL_METHOD(inline void)::ResizeFor(size_t index)
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this->data = ReallocT(this->data, new_size);
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MemSetT(this->data + this->size, 0, new_size - this->size);
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this->used_bitmap.resize(Align(new_size, BITMAP_SIZE) / BITMAP_SIZE);
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if (this->size % BITMAP_SIZE != 0) {
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/* Already-allocated bits above old size are now unused. */
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this->used_bitmap[this->size / BITMAP_SIZE] &= ~((~static_cast<BitmapStorage>(0)) << (this->size % BITMAP_SIZE));
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}
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if (new_size % BITMAP_SIZE != 0) {
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/* Bits above new size are considered used. */
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this->used_bitmap[new_size / BITMAP_SIZE] |= (~static_cast<BitmapStorage>(0)) << (new_size % BITMAP_SIZE);
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}
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this->size = new_size;
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}
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@ -69,25 +80,20 @@ DEFINE_POOL_METHOD(inline void)::ResizeFor(size_t index)
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*/
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DEFINE_POOL_METHOD(inline size_t)::FindFirstFree()
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{
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size_t index = this->first_free;
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for (; index < this->first_unused; index++) {
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if (this->data[index] == nullptr) return index;
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for (auto it = std::next(std::begin(this->used_bitmap), this->first_free / BITMAP_SIZE); it != std::end(this->used_bitmap); ++it) {
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BitmapStorage available = ~(*it);
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if (available == 0) continue;
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return std::distance(std::begin(this->used_bitmap), it) * BITMAP_SIZE + FindFirstBit(available);
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}
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if (index < this->size) {
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return index;
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}
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assert(index == this->size);
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assert(this->first_unused == this->size);
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if (index < Tmax_size) {
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this->ResizeFor(index);
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return index;
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if (this->first_unused < Tmax_size) {
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this->ResizeFor(this->first_unused);
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return this->first_unused;
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}
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assert(this->items == Tmax_size);
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assert(this->first_unused == Tmax_size);
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return NO_FREE_ITEM;
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}
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@ -122,6 +128,7 @@ DEFINE_POOL_METHOD(inline void *)::AllocateItem(size_t size, size_t index)
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item = (Titem *)MallocT<byte>(size);
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}
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this->data[index] = item;
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SetBit(this->used_bitmap[index / BITMAP_SIZE], index % BITMAP_SIZE);
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item->index = (Tindex)(uint)index;
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return item;
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}
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@ -190,7 +197,10 @@ DEFINE_POOL_METHOD(void)::FreeItem(size_t index)
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this->data[index] = nullptr;
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this->first_free = std::min(this->first_free, index);
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this->items--;
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if (!this->cleaning) Titem::PostDestructor(index);
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if (!this->cleaning) {
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ClrBit(this->used_bitmap[index / BITMAP_SIZE], index % BITMAP_SIZE);
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Titem::PostDestructor(index);
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}
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}
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/** Destroys all items in the pool and resets all member variables. */
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@ -202,6 +212,8 @@ DEFINE_POOL_METHOD(void)::CleanPool()
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}
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assert(this->items == 0);
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free(this->data);
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this->used_bitmap.clear();
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this->used_bitmap.shrink_to_fit();
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this->first_unused = this->first_free = this->size = 0;
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this->data = nullptr;
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this->cleaning = false;
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@ -83,6 +83,9 @@ struct Pool : PoolBase {
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static constexpr size_t MAX_SIZE = Tmax_size; ///< Make template parameter accessible from outside
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using BitmapStorage = size_t;
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static constexpr size_t BITMAP_SIZE = std::numeric_limits<BitmapStorage>::digits;
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const char * const name; ///< Name of this pool
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size_t size; ///< Current allocated size
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@ -95,6 +98,7 @@ struct Pool : PoolBase {
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bool cleaning; ///< True if cleaning pool (deleting all items)
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Titem **data; ///< Pointer to array of pointers to Titem
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std::vector<BitmapStorage> used_bitmap; ///< Bitmap of used indices.
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Pool(const char *name);
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void CleanPool() override;
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