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kernel/vm_manager: Reserve memory ahead of time for slow path in MergeAdjacentVMA

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Avoids potentially expensive (depending on the size of the memory block)
allocations by reserving the necessary memory before performing both
insertions. This avoids scenarios where the second insert may cause a
reallocation to occur.
This commit is contained in:
Lioncash 2019-07-24 07:24:19 -04:00
parent a43ee8d752
commit 56c6f767ae
1 changed files with 4 additions and 1 deletions
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5
src/core/hle/kernel/vm_manager.cpp
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@ -765,11 +765,14 @@ void VMManager::MergeAdjacentVMA(VirtualMemoryArea& left, const VirtualMemoryAre
// Fast case: left is an entire backing block.
left.backing_block->insert(left.backing_block->end(), right_begin, right_end);
} else {
// Slow case: make a new memory block for left and right.
const auto left_begin = left.backing_block->begin() + left.offset;
const auto left_end = left_begin + left.size;
const auto left_size = static_cast<std::size_t>(std::distance(left_begin, left_end));
const auto right_size = static_cast<std::size_t>(std::distance(right_begin, right_end));
// Slow case: make a new memory block for left and right.
auto new_memory = std::make_shared<PhysicalMemory>();
new_memory->reserve(left_size + right_size);
new_memory->insert(new_memory->end(), left_begin, left_end);
new_memory->insert(new_memory->end(), right_begin, right_end);