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Resource Management 3: Buddy allocator

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Introduces the buddy system for fast power-of-two sub-allocation.

BUG=dawn:27

Change-Id: I56836ae317ecc5a91d8341c843fc37d4f91fb5af
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/9260
Reviewed-by: Kai Ninomiya <kainino@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
This commit is contained in:
Bryan Bernhart 2019-07-30 16:46:10 +00:00 committed by Commit Bot service account
parent 7b57c5bb77
commit 35ad5221fb
4 changed files with 706 additions and 0 deletions
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3
BUILD.gn
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@ -112,6 +112,8 @@ source_set("libdawn_native_sources") {
"src/dawn_native/BindGroup.h",
"src/dawn_native/BindGroupLayout.cpp",
"src/dawn_native/BindGroupLayout.h",
"src/dawn_native/BuddyAllocator.cpp",
"src/dawn_native/BuddyAllocator.h",
"src/dawn_native/Buffer.cpp",
"src/dawn_native/Buffer.h",
"src/dawn_native/CommandAllocator.cpp",
@ -598,6 +600,7 @@ test("dawn_unittests") {
]
sources += [
"src/tests/unittests/BitSetIteratorTests.cpp",
"src/tests/unittests/BuddyAllocatorTests.cpp",
"src/tests/unittests/CommandAllocatorTests.cpp",
"src/tests/unittests/EnumClassBitmasksTests.cpp",
"src/tests/unittests/ErrorTests.cpp",

267
src/dawn_native/BuddyAllocator.cpp Normal file
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@ -0,0 +1,267 @@
// Copyright 2019 The Dawn Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "dawn_native/BuddyAllocator.h"
#include "common/Assert.h"
#include "common/Math.h"
namespace dawn_native {
BuddyAllocator::BuddyAllocator(uint64_t maxSize) : mMaxBlockSize(maxSize) {
ASSERT(IsPowerOfTwo(maxSize));
mFreeLists.resize(Log2(mMaxBlockSize) + 1);
// Insert the level0 free block.
mRoot = new BuddyBlock(maxSize, /*offset*/ 0);
mFreeLists[0] = {mRoot};
}
BuddyAllocator::~BuddyAllocator() {
if (mRoot) {
DeleteBlock(mRoot);
}
}
uint64_t BuddyAllocator::ComputeTotalNumOfFreeBlocksForTesting() const {
return ComputeNumOfFreeBlocks(mRoot);
}
uint64_t BuddyAllocator::ComputeNumOfFreeBlocks(BuddyBlock* block) const {
if (block->mState == BlockState::Free) {
return 1;
} else if (block->mState == BlockState::Split) {
return ComputeNumOfFreeBlocks(block->split.pLeft) +
ComputeNumOfFreeBlocks(block->split.pLeft->pBuddy);
}
return 0;
}
uint32_t BuddyAllocator::ComputeLevelFromBlockSize(uint64_t blockSize) const {
// Every level in the buddy system can be indexed by order-n where n = log2(blockSize).
// However, mFreeList zero-indexed by level.
// For example, blockSize=4 is Level1 if MAX_BLOCK is 8.
return Log2(mMaxBlockSize) - Log2(blockSize);
}
uint64_t BuddyAllocator::GetNextFreeAlignedBlock(size_t allocationBlockLevel,
uint64_t alignment) const {
ASSERT(IsPowerOfTwo(alignment));
// The current level is the level that corresponds to the allocation size. The free list may
// not contain a block at that level until a larger one gets allocated (and splits).
// Continue to go up the tree until such a larger block exists.
//
// Even if the block exists at the level, it cannot be used if it's offset is unaligned.
// When the alignment is also a power-of-two, we simply use the next free block whose size
// is greater than or equal to the alignment value.
//
// After one 8-byte allocation:
//
// Level --------------------------------
// 0 32 | S |
// --------------------------------
// 1 16 | S | F2 | S - split
// -------------------------------- F - free
// 2 8 | Aa | F1 | | A - allocated
// --------------------------------
//
// Allocate(size=8, alignment=8) will be satisfied by using F1.
// Allocate(size=8, alignment=4) will be satified by using F1.
// Allocate(size=8, alignment=16) will be satisified by using F2.
//
for (size_t currLevel = allocationBlockLevel; currLevel >= 0; currLevel--) {
BuddyBlock* freeBlock = mFreeLists[currLevel].head;
if (freeBlock && (freeBlock->mOffset % alignment == 0)) {
return currLevel;
}
if (currLevel == 0) {
break;
}
}
return INVALID_OFFSET; // No free block exists at any level.
}
// Inserts existing free block into the free-list.
// Called by allocate upon splitting to insert a child block into a free-list.
// Note: Always insert into the head of the free-list. As when a larger free block at a lower
// level was split, there were no smaller free blocks at a higher level to allocate.
void BuddyAllocator::InsertFreeBlock(BuddyBlock* block, size_t level) {
ASSERT(block->mState == BlockState::Free);
// Inserted block is now the front (no prev).
block->free.pPrev = nullptr;
// Old head is now the inserted block's next.
block->free.pNext = mFreeLists[level].head;
// Block already in HEAD position (ex. right child was inserted first).
if (mFreeLists[level].head != nullptr) {
// Old head's previous is the inserted block.
mFreeLists[level].head->free.pPrev = block;
}
mFreeLists[level].head = block;
}
void BuddyAllocator::RemoveFreeBlock(BuddyBlock* block, size_t level) {
ASSERT(block->mState == BlockState::Free);
if (mFreeLists[level].head == block) {
// Block is in HEAD position.
mFreeLists[level].head = mFreeLists[level].head->free.pNext;
} else {
// Block is after HEAD position.
BuddyBlock* pPrev = block->free.pPrev;
BuddyBlock* pNext = block->free.pNext;
ASSERT(pPrev != nullptr);
ASSERT(pPrev->mState == BlockState::Free);
pPrev->free.pNext = pNext;
if (pNext != nullptr) {
ASSERT(pNext->mState == BlockState::Free);
pNext->free.pPrev = pPrev;
}
}
}
uint64_t BuddyAllocator::Allocate(uint64_t allocationSize, uint64_t alignment) {
if (allocationSize == 0 || allocationSize > mMaxBlockSize) {
return INVALID_OFFSET;
}
// Compute the level
const uint32_t allocationSizeToLevel = ComputeLevelFromBlockSize(allocationSize);
ASSERT(allocationSizeToLevel < mFreeLists.size());
uint64_t currBlockLevel = GetNextFreeAlignedBlock(allocationSizeToLevel, alignment);
// Error when no free blocks exist (allocator is full)
if (currBlockLevel == INVALID_OFFSET) {
return INVALID_OFFSET;
}
// Split free blocks level-by-level.
// Terminate when the current block level is equal to the computed level of the requested
// allocation.
BuddyBlock* currBlock = mFreeLists[currBlockLevel].head;
for (; currBlockLevel < allocationSizeToLevel; currBlockLevel++) {
ASSERT(currBlock->mState == BlockState::Free);
// Remove curr block (about to be split).
RemoveFreeBlock(currBlock, currBlockLevel);
// Create two free child blocks (the buddies).
const uint64_t nextLevelSize = currBlock->mSize / 2;
BuddyBlock* leftChildBlock = new BuddyBlock(nextLevelSize, currBlock->mOffset);
BuddyBlock* rightChildBlock =
new BuddyBlock(nextLevelSize, currBlock->mOffset + nextLevelSize);
// Remember the parent to merge these back upon de-allocation.
rightChildBlock->pParent = currBlock;
leftChildBlock->pParent = currBlock;
// Make them buddies.
leftChildBlock->pBuddy = rightChildBlock;
rightChildBlock->pBuddy = leftChildBlock;
// Insert the children back into the free list into the next level.
// The free list does not require a specific order. However, an order is specified as
// it's ideal to allocate lower addresses first by having the leftmost child in HEAD.
InsertFreeBlock(rightChildBlock, currBlockLevel + 1);
InsertFreeBlock(leftChildBlock, currBlockLevel + 1);
// Curr block is now split.
currBlock->mState = BlockState::Split;
currBlock->split.pLeft = leftChildBlock;
// Decend down into the next level.
currBlock = leftChildBlock;
}
// Remove curr block from free-list (now allocated).
RemoveFreeBlock(currBlock, currBlockLevel);
currBlock->mState = BlockState::Allocated;
return currBlock->mOffset;
}
void BuddyAllocator::Deallocate(uint64_t offset) {
BuddyBlock* curr = mRoot;
// TODO(bryan.bernhart@intel.com): Optimize de-allocation.
// Passing allocationSize directly will avoid the following level-by-level search;
// however, it requires the size information to be stored outside the allocator.
// Search for the free block node that corresponds to the block offset.
size_t currBlockLevel = 0;
while (curr->mState == BlockState::Split) {
if (offset < curr->split.pLeft->pBuddy->mOffset) {
curr = curr->split.pLeft;
} else {
curr = curr->split.pLeft->pBuddy;
}
currBlockLevel++;
}
ASSERT(curr->mState == BlockState::Allocated);
// Ensure the block is at the correct level
ASSERT(currBlockLevel == ComputeLevelFromBlockSize(curr->mSize));
// Mark curr free so we can merge.
curr->mState = BlockState::Free;
// Merge the buddies (LevelN-to-Level0).
while (currBlockLevel > 0 && curr->pBuddy->mState == BlockState::Free) {
// Remove the buddy.
RemoveFreeBlock(curr->pBuddy, currBlockLevel);
BuddyBlock* parent = curr->pParent;
// The buddies were inserted in a specific order but
// could be deleted in any order.
DeleteBlock(curr->pBuddy);
DeleteBlock(curr);
// Parent is now free.
parent->mState = BlockState::Free;
// Ascend up to the next level (parent block).
curr = parent;
currBlockLevel--;
}
InsertFreeBlock(curr, currBlockLevel);
}
// Helper which deletes a block in the tree recursively (post-order).
void BuddyAllocator::DeleteBlock(BuddyBlock* block) {
ASSERT(block != nullptr);
if (block->mState == BlockState::Split) {
// Delete the pair in same order we inserted.
DeleteBlock(block->split.pLeft->pBuddy);
DeleteBlock(block->split.pLeft);
}
delete block;
}
} // namespace dawn_native

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src/dawn_native/BuddyAllocator.h Normal file
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@ -0,0 +1,111 @@
// Copyright 2019 The Dawn Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef DAWNNATIVE_BUDDYALLOCATOR_H_
#define DAWNNATIVE_BUDDYALLOCATOR_H_
#include <cstddef>
#include <vector>
namespace dawn_native {
static constexpr uint64_t INVALID_OFFSET = std::numeric_limits<uint64_t>::max();
// Buddy allocator uses the buddy memory allocation technique to satisify an allocation request.
// Memory is split into halves until just large enough to fit to the request. This
// requires the allocation size to be a power-of-two value. The allocator "allocates" a block by
// returning the starting offset whose size is guaranteed to be greater than or equal to the
// allocation size. To deallocate, the same offset is used to find the corresponding block.
//
// Internally, it manages a free list to track free blocks in a full binary tree.
// Every index in the free list corresponds to a level in the tree. That level also determines
// the size of the block to be used to satisfy the request. The first level (index=0) represents
// the root whose size is also called the max block size.
//
class BuddyAllocator {
public:
BuddyAllocator(uint64_t maxSize);
~BuddyAllocator();
// Required methods.
uint64_t Allocate(uint64_t allocationSize, uint64_t alignment = 1);
void Deallocate(uint64_t offset);
// For testing purposes only.
uint64_t ComputeTotalNumOfFreeBlocksForTesting() const;
private:
uint32_t ComputeLevelFromBlockSize(uint64_t blockSize) const;
uint64_t GetNextFreeAlignedBlock(size_t allocationBlockLevel, uint64_t alignment) const;
enum class BlockState { Free, Split, Allocated };
struct BuddyBlock {
BuddyBlock(uint64_t size, uint64_t offset)
: mOffset(offset), mSize(size), mState(BlockState::Free) {
free.pPrev = nullptr;
free.pNext = nullptr;
}
uint64_t mOffset;
uint64_t mSize;
// Pointer to this block's buddy, iff parent is split.
// Used to quickly merge buddy blocks upon de-allocate.
BuddyBlock* pBuddy = nullptr;
BuddyBlock* pParent = nullptr;
// Track whether this block has been split or not.
BlockState mState;
union {
// Used upon allocation.
// Avoids searching for the next free block.
struct {
BuddyBlock* pPrev;
BuddyBlock* pNext;
} free;
// Used upon de-allocation.
// Had this block split upon allocation, it and it's buddy is to be deleted.
struct {
BuddyBlock* pLeft;
} split;
};
};
void InsertFreeBlock(BuddyBlock* block, size_t level);
void RemoveFreeBlock(BuddyBlock* block, size_t level);
void DeleteBlock(BuddyBlock* block);
uint64_t ComputeNumOfFreeBlocks(BuddyBlock* block) const;
// Keep track the head and tail (for faster insertion/removal).
struct BlockList {
BuddyBlock* head = nullptr; // First free block in level.
// TODO(bryan.bernhart@intel.com): Track the tail.
};
BuddyBlock* mRoot = nullptr; // Used to deallocate non-free blocks.
uint64_t mMaxBlockSize = 0;
// List of linked-lists of free blocks where the index is a level that
// corresponds to a power-of-two sized block.
std::vector<BlockList> mFreeLists;
};
} // namespace dawn_native
#endif // DAWNNATIVE_BUDDYALLOCATOR_H_

325
src/tests/unittests/BuddyAllocatorTests.cpp Normal file
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@ -0,0 +1,325 @@
// Copyright 2019 The Dawn Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <gtest/gtest.h>
#include "dawn_native/BuddyAllocator.h"
using namespace dawn_native;
// Verify the buddy allocator with a basic test.
TEST(BuddyAllocatorTests, SingleBlock) {
// After one 32 byte allocation:
//
// Level --------------------------------
// 0 32 | A |
// --------------------------------
//
constexpr uint64_t maxBlockSize = 32;
BuddyAllocator allocator(maxBlockSize);
// Check that we cannot allocate a oversized block.
ASSERT_EQ(allocator.Allocate(maxBlockSize * 2), INVALID_OFFSET);
// Check that we cannot allocate a zero sized block.
ASSERT_EQ(allocator.Allocate(0u), INVALID_OFFSET);
// Allocate the block.
uint64_t blockOffset = allocator.Allocate(maxBlockSize);
ASSERT_EQ(blockOffset, 0u);
// Check that we are full.
ASSERT_EQ(allocator.Allocate(maxBlockSize), INVALID_OFFSET);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 0u);
// Deallocate the block.
allocator.Deallocate(blockOffset);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 1u);
}
// Verify multiple allocations succeeds using a buddy allocator.
TEST(BuddyAllocatorTests, MultipleBlocks) {
// Fill every level in the allocator (order-n = 2^n)
const uint64_t maxBlockSize = (1ull << 16);
for (uint64_t order = 1; (1ull << order) <= maxBlockSize; order++) {
BuddyAllocator allocator(maxBlockSize);
uint64_t blockSize = (1ull << order);
for (uint32_t blocki = 0; blocki < (maxBlockSize / blockSize); blocki++) {
ASSERT_EQ(allocator.Allocate(blockSize), blockSize * blocki);
}
}
}
// Verify that a single allocation succeeds using a buddy allocator.
TEST(BuddyAllocatorTests, SingleSplitBlock) {
// After one 8 byte allocation:
//
// Level --------------------------------
// 0 32 | S |
// --------------------------------
// 1 16 | S | F | S - split
// -------------------------------- F - free
// 2 8 | A | F | | | A - allocated
// --------------------------------
//
constexpr uint64_t maxBlockSize = 32;
BuddyAllocator allocator(maxBlockSize);
// Allocate block (splits two blocks).
uint64_t blockOffset = allocator.Allocate(8);
ASSERT_EQ(blockOffset, 0u);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 2u);
// Deallocate block (merges two blocks).
allocator.Deallocate(blockOffset);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 1u);
// Check that we cannot allocate a block that is oversized.
ASSERT_EQ(allocator.Allocate(maxBlockSize * 2), INVALID_OFFSET);
// Re-allocate the largest block allowed after merging.
blockOffset = allocator.Allocate(maxBlockSize);
ASSERT_EQ(blockOffset, 0u);
allocator.Deallocate(blockOffset);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 1u);
}
// Verify that a multiple allocated blocks can be removed in the free-list.
TEST(BuddyAllocatorTests, MultipleSplitBlocks) {
// After four 16 byte allocations:
//
// Level --------------------------------
// 0 32 | S |
// --------------------------------
// 1 16 | S | S | S - split
// -------------------------------- F - free
// 2 8 | Aa | Ab | Ac | Ad | A - allocated
// --------------------------------
//
constexpr uint64_t maxBlockSize = 32;
BuddyAllocator allocator(maxBlockSize);
// Populates the free-list with four blocks at Level2.
// Allocate "a" block (two splits).
constexpr uint64_t blockSizeInBytes = 8;
uint64_t blockOffsetA = allocator.Allocate(blockSizeInBytes);
ASSERT_EQ(blockOffsetA, 0u);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 2u);
// Allocate "b" block.
uint64_t blockOffsetB = allocator.Allocate(blockSizeInBytes);
ASSERT_EQ(blockOffsetB, blockSizeInBytes);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 1u);
// Allocate "c" block (three splits).
uint64_t blockOffsetC = allocator.Allocate(blockSizeInBytes);
ASSERT_EQ(blockOffsetC, blockOffsetB + blockSizeInBytes);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 1u);
// Allocate "d" block.
uint64_t blockOffsetD = allocator.Allocate(blockSizeInBytes);
ASSERT_EQ(blockOffsetD, blockOffsetC + blockSizeInBytes);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 0u);
// Deallocate "d" block.
// FreeList[Level2] = [BlockD] -> x
allocator.Deallocate(blockOffsetD);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 1u);
// Deallocate "b" block.
// FreeList[Level2] = [BlockB] -> [BlockD] -> x
allocator.Deallocate(blockOffsetB);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 2u);
// Deallocate "c" block (one merges).
// FreeList[Level1] = [BlockCD] -> x
// FreeList[Level2] = [BlockB] -> x
allocator.Deallocate(blockOffsetC);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 2u);
// Deallocate "a" block (two merges).
// FreeList[Level0] = [BlockABCD] -> x
allocator.Deallocate(blockOffsetA);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 1u);
}
// Verify the buddy allocator can handle allocations of various sizes.
TEST(BuddyAllocatorTests, MultipleSplitBlockIncreasingSize) {
// After four Level4-to-Level1 byte then one L4 block allocations:
//
// Level -----------------------------------------------------------------
// 0 512 | S |
// -----------------------------------------------------------------
// 1 256 | S | A |
// -----------------------------------------------------------------
// 2 128 | S | A | | |
// -----------------------------------------------------------------
// 3 64 | S | A | | | | | | |
// -----------------------------------------------------------------
// 4 32 | A | F | | | | | | | | | | | | | | |
// -----------------------------------------------------------------
//
constexpr uint64_t maxBlockSize = 512;
BuddyAllocator allocator(maxBlockSize);
ASSERT_EQ(allocator.Allocate(32), 0ull);
ASSERT_EQ(allocator.Allocate(64), 64ull);
ASSERT_EQ(allocator.Allocate(128), 128ull);
ASSERT_EQ(allocator.Allocate(256), 256ull);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 1u);
// Fill in the last free block.
ASSERT_EQ(allocator.Allocate(32), 32ull);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 0u);
// Check if we're full.
ASSERT_EQ(allocator.Allocate(32), INVALID_OFFSET);
}
// Verify very small allocations using a larger allocator works correctly.
TEST(BuddyAllocatorTests, MultipleSplitBlocksVariableSizes) {
// After allocating four pairs of one 64 byte block and one 32 byte block.
//
// Level -----------------------------------------------------------------
// 0 512 | S |
// -----------------------------------------------------------------
// 1 256 | S | S |
// -----------------------------------------------------------------
// 2 128 | S | S | S | F |
// -----------------------------------------------------------------
// 3 64 | A | S | A | A | S | A | | |
// -----------------------------------------------------------------
// 4 32 | | | A | A | | | | | A | A | | | | | | |
// -----------------------------------------------------------------
//
constexpr uint64_t maxBlockSize = 512;
BuddyAllocator allocator(maxBlockSize);
ASSERT_EQ(allocator.Allocate(64), 0ull);
ASSERT_EQ(allocator.Allocate(32), 64ull);
ASSERT_EQ(allocator.Allocate(64), 128ull);
ASSERT_EQ(allocator.Allocate(32), 96ull);
ASSERT_EQ(allocator.Allocate(64), 192ull);
ASSERT_EQ(allocator.Allocate(32), 256ull);
ASSERT_EQ(allocator.Allocate(64), 320ull);
ASSERT_EQ(allocator.Allocate(32), 288ull);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 1u);
}
// Verify the buddy allocator can deal with bad fragmentation.
TEST(BuddyAllocatorTests, MultipleSplitBlocksInterleaved) {
// Allocate every leaf then de-allocate every other of those allocations.
//
// Level -----------------------------------------------------------------
// 0 512 | S |
// -----------------------------------------------------------------
// 1 256 | S | S |
// -----------------------------------------------------------------
// 2 128 | S | S | S | S |
// -----------------------------------------------------------------
// 3 64 | S | S | S | S | S | S | S | S |
// -----------------------------------------------------------------
// 4 32 | A | F | A | F | A | F | A | F | A | F | A | F | A | F | A | F |
// -----------------------------------------------------------------
//
constexpr uint64_t maxBlockSize = 512;
BuddyAllocator allocator(maxBlockSize);
// Allocate leaf blocks
constexpr uint64_t minBlockSizeInBytes = 32;
std::vector<uint64_t> blockOffsets;
for (uint64_t i = 0; i < maxBlockSize / minBlockSizeInBytes; i++) {
blockOffsets.push_back(allocator.Allocate(minBlockSizeInBytes));
}
// Free every other leaf block.
for (size_t count = 1; count < blockOffsets.size(); count += 2) {
allocator.Deallocate(blockOffsets[count]);
}
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 8u);
}
// Verify the buddy allocator can deal with multiple allocations with mixed alignments.
TEST(BuddyAllocatorTests, SameSizeVariousAlignment) {
// After two 8 byte allocations with 16 byte alignment then one 8 byte allocation with 8 byte
// alignment.
//
// Level --------------------------------
// 0 32 | S |
// --------------------------------
// 1 16 | S | S | S - split
// -------------------------------- F - free
// 2 8 | Aa | F | Ab | Ac | A - allocated
// --------------------------------
//
BuddyAllocator allocator(32);
// Allocate Aa (two splits).
ASSERT_EQ(allocator.Allocate(8, 16), 0u);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 2u);
// Allocate Ab (skip Aa buddy due to alignment and perform another split).
ASSERT_EQ(allocator.Allocate(8, 16), 16u);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 2u);
// Check that we cannot fit another.
ASSERT_EQ(allocator.Allocate(8, 16), INVALID_OFFSET);
// Allocate Ac (zero splits and Ab's buddy is now the first free block).
ASSERT_EQ(allocator.Allocate(8, 8), 24u);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 1u);
}
// Verify the buddy allocator can deal with multiple allocations with equal alignments.
TEST(BuddyAllocatorTests, VariousSizeSameAlignment) {
// After two 8 byte allocations with 4 byte alignment then one 16 byte allocation with 4 byte
// alignment.
//
// Level --------------------------------
// 0 32 | S |
// --------------------------------
// 1 16 | S | Ac | S - split
// -------------------------------- F - free
// 2 8 | Aa | Ab | | A - allocated
// --------------------------------
//
constexpr uint64_t maxBlockSize = 32;
constexpr uint64_t alignment = 4;
BuddyAllocator allocator(maxBlockSize);
// Allocate block Aa (two splits)
ASSERT_EQ(allocator.Allocate(8, alignment), 0u);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 2u);
// Allocate block Ab (Aa's buddy)
ASSERT_EQ(allocator.Allocate(8, alignment), 8u);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 1u);
// Check that we can still allocate Ac.
ASSERT_EQ(allocator.Allocate(16, alignment), 16ull);
ASSERT_EQ(allocator.ComputeTotalNumOfFreeBlocksForTesting(), 0u);
}