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Eliminate slab copies during allocation. #943

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merged 1 commit into from
Sep 6, 2023
Merged

Eliminate slab copies during allocation. #943

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41 changes: 22 additions & 19 deletions src/gpgmm/common/SlabMemoryAllocator.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,14 @@ namespace gpgmm {
: Allocator(blockCount, blockSize), IndexInList(indexInList) {
}

Slab(Slab&& other)
: Allocator(std::move(other.Allocator)),
UsedBlocksPerSlab(std::move(other.UsedBlocksPerSlab)),
Allocation(std::move(other.Allocation)),
IndexInList(std::move(other.IndexInList)),
IndexInCache(std::move(other.IndexInCache)) {
}

uint64_t GetBlockCount() const {
return Allocator.GetBlockCount();
}
Expand All @@ -71,7 +79,7 @@ namespace gpgmm {

SlabBlockAllocator Allocator;
uint64_t UsedBlocksPerSlab = 0;
MemoryAllocationBase Allocation;
std::unique_ptr<MemoryAllocationBase> Allocation;
uint64_t IndexInList = kInvalidIndex;
uint64_t IndexInCache = kInvalidIndex;
};
Expand Down Expand Up @@ -173,12 +181,12 @@ namespace gpgmm {
const Slab& freeSlab = cache->FreeList.back();

// Slab is not free if only the block exists.
if (freeSlab.Allocation.GetMemory() == nullptr) {
if (freeSlab.Allocation == nullptr) {
continue;
}

if (freeSlab.Allocation.GetSize() >= slabSize) {
return freeSlab.Allocation.GetSize();
if (freeSlab.Allocation->GetSize() >= slabSize) {
return freeSlab.Allocation->GetSize();
}
}

Expand Down Expand Up @@ -268,8 +276,8 @@ namespace gpgmm {
&pFreeSlab->Allocator, mBlockSize, request.Alignment, request.NeverAllocate,
[&](const auto& block) -> ResultOrError<std::unique_ptr<MemoryAllocationBase>> {
// Re-use memory from the free slab.
if (pFreeSlab->Allocation.GetMemory() != nullptr) {
return std::make_unique<MemoryAllocationBase>(pFreeSlab->Allocation);
if (pFreeSlab->Allocation != nullptr) {
return std::make_unique<MemoryAllocationBase>(*pFreeSlab->Allocation);
}

// Or use pre-fetched memory if possible. Else, throw it away and create a new
Expand All @@ -285,9 +293,9 @@ namespace gpgmm {
// Assign pre-fetched memory to the slab.
if (prefetchedSlabAllocation != nullptr &&
prefetchedSlabAllocation->GetSize() == slabSize) {
pFreeSlab->Allocation = *prefetchedSlabAllocation;
pFreeSlab->Allocation.reset(prefetchedSlabAllocation.release());
mStats.PrefetchedMemoryMissesEliminated++;
return std::make_unique<MemoryAllocationBase>(pFreeSlab->Allocation);
return std::make_unique<MemoryAllocationBase>(*pFreeSlab->Allocation);
}

if (prefetchedSlabAllocation != nullptr) {
Expand All @@ -307,13 +315,10 @@ namespace gpgmm {
newSlabRequest.SizeInBytes = slabSize;
newSlabRequest.Alignment = mSlabAlignment;

std::unique_ptr<MemoryAllocationBase> slabAllocation;
GPGMM_TRY_ASSIGN(mMemoryAllocator->TryAllocateMemory(newSlabRequest),
slabAllocation);

pFreeSlab->Allocation = *slabAllocation;
pFreeSlab->Allocation);

return std::make_unique<MemoryAllocationBase>(pFreeSlab->Allocation);
return std::make_unique<MemoryAllocationBase>(*pFreeSlab->Allocation);
}),
subAllocation);

Expand Down Expand Up @@ -382,7 +387,7 @@ namespace gpgmm {

// Since the slab's block could reside in another allocated block, the allocation
// offset must be made relative to the slab's underlying memory and not the slab itself.
const uint64_t offsetFromMemory = pFreeSlab->Allocation.GetOffset() + blockInSlab->Offset;
const uint64_t offsetFromMemory = pFreeSlab->Allocation->GetOffset() + blockInSlab->Offset;

mStats.UsedBlockCount++;
mStats.UsedBlockUsage += blockInSlab->Size;
Expand All @@ -407,7 +412,7 @@ namespace gpgmm {
Slab* pSlab = *(blockInSlab->ppSlab);
ASSERT(pSlab != nullptr);

SlabCache* pCache = GetOrCreateCache(pSlab->Allocation.GetSize());
SlabCache* pCache = GetOrCreateCache(pSlab->Allocation->GetSize());
ASSERT(pCache != nullptr);

// Move the slab from the full-list to free-list.
Expand All @@ -428,9 +433,7 @@ namespace gpgmm {
slabMemory->Unref();

if (pSlab->IsEmpty()) {
mMemoryAllocator->DeallocateMemory(
std::make_unique<MemoryAllocationBase>(pSlab->Allocation));
pSlab->Allocation = {}; // Invalidate it
mMemoryAllocator->DeallocateMemory(std::move(pSlab->Allocation));
}
}

Expand All @@ -440,7 +443,7 @@ namespace gpgmm {
StableList<Slab>* pDstList) {
const uint64_t srcIndex = pSlab->IndexInList;
pSlab->IndexInList = pDstList->size();
pDstList->push_back(*pSlab); // copy
pDstList->push_back(std::move(*pSlab));
pSrcList->erase(srcIndex);
pSlab = &pDstList->back();

Expand Down