Compute aligned size class arithmetically - #372
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get_size_info_align previously scanned the size class table linearly from the class matching the requested size until it found one whose size was a multiple of the alignment, costing up to ~28 iterations (e.g. a small allocation with page-sized alignment). Rounding the size up to a multiple of the (power of 2) alignment and then to a size class always lands on the smallest class whose size is a multiple of the alignment, since get_size_info rounds up to a power-of-2 spacing which preserves divisibility by the alignment. This makes the lookup constant time, which should improve memory-aligned (de)llocations. Verified equivalent to the previous scan for every size and alignment in both the default and extended size class configurations.
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get_size_info_align previously scanned the size class table linearly from the class matching the requested size until it found one whose size was a multiple of the alignment, costing up to ~28 iterations (e.g. a small allocation with page-sized alignment).
Rounding the size up to a multiple of the (power of 2) alignment and then to a size class always lands on the smallest class whose size is a multiple of the alignment, since get_size_info rounds up to a power-of-2 spacing which preserves divisibility by the alignment. This makes the lookup constant time, which should improve memory-aligned (de)llocations.
Verified equivalent to the previous scan for every size and alignment in both the default and extended size class configurations.