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Port of [OffsetAllocator](https://github.com/sebbbi/OffsetAllocator) by (C) Sebastian Aaltonen 2023 in JAI
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/* | |
Port of [OffsetAllocator](https://github.com/sebbbi/OffsetAllocator) by (C) Sebastian Aaltonen 2023 | |
MIT License | |
Copyright (c) 2023 Sebastian Aaltonen | |
Permission is hereby granted, free of charge, to any person obtaining a copy | |
of this software and associated documentation files (the "Software"), to deal | |
in the Software without restriction, including without limitation the rights | |
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | |
copies of the Software, and to permit persons to whom the Software is | |
furnished to do so, subject to the following conditions: | |
The above copyright notice and this permission notice shall be included in all | |
copies or substantial portions of the Software. | |
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | |
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | |
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | |
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | |
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | |
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE | |
SOFTWARE. | |
*/ | |
#module_parameters(USE_16_BIT_NODE_INDICES := false, DEBUG_VERBOSE := false); | |
OAllocation :: struct { | |
NO_SPACE:u32: 0xffffffff; | |
offset:= NO_SPACE; | |
metadata:NodeIndex= NO_SPACE.(NodeIndex, trunc); // internal: node index | |
} | |
OStorageReport :: struct { | |
totalFreeSpace: u32; | |
largestFreeRegion: u32; | |
} | |
OStorageReportFull :: struct { | |
Region :: struct { | |
size: u32; | |
count: u32; | |
} | |
freeRegions:[NUM_LEAF_BINS]Region; | |
} | |
OAllocator :: struct { | |
Node :: struct { | |
unused :NodeIndex: (0xffffffff).(NodeIndex, trunc); | |
dataOffset: u32; | |
dataSize: u32; | |
binListPrev:= unused; | |
binListNext:= unused; | |
neighborPrev:= unused; | |
neighborNext:= unused; | |
used:= false; // TODO: Merge as bit flag | |
} | |
m_size: u32; | |
m_freeStorage: u32; | |
m_usedBinsTop: u32; | |
m_usedBins: [NUM_TOP_BINS]u8; | |
m_binIndices: [NUM_LEAF_BINS]NodeIndex; | |
m_nodes: []Node; | |
m_freeNodes: *NodeIndex; | |
m_freeOffset: u32; | |
} | |
oalloc_init :: (using this: *OAllocator, size: u32, maxAllocs: u32 = 128 * 1024) { | |
m_size = size; | |
m_nodes = .{}; | |
m_freeNodes = null; | |
oalloc_reset(this, maxAllocs); | |
} | |
oalloc_reset :: (using this: *OAllocator, maxAllocs: u32) { | |
#if (size_of(NodeIndex) == 2) { | |
assert(maxAllocs <= 65536); | |
} | |
m_freeStorage = 0; | |
m_usedBinsTop = 0; | |
m_freeOffset = maxAllocs - 1; | |
for * m_usedBins { | |
it.* = 0; | |
} | |
for * m_binIndices { | |
it.* = Node.unused; | |
} | |
// what?? | |
if (m_nodes) then free(m_nodes.data); | |
if (m_freeNodes) then free(m_freeNodes); | |
m_nodes = NewArray(maxAllocs, Node); | |
freeNodes := NewArray(maxAllocs, NodeIndex); | |
m_freeNodes = freeNodes.data; | |
// Freelist is a stack. Nodes in inverse order so that [0] pops first. | |
for * freeNodes { | |
it.* = xx (maxAllocs - it_index - 1); | |
} | |
// Start state: Whole storage as one big node | |
// Algorithm will split remainders and push them back as smaller nodes | |
insertNodeIntoBin(this, m_size, 0); | |
} | |
oalloc_destroy :: (using this: *OAllocator) { | |
free(m_nodes.data); | |
free(m_freeNodes); | |
} | |
oalloc_allocate :: (using this: *OAllocator, size: u32) -> OAllocation { | |
// Out of allocations? | |
if (m_freeOffset == 0) { | |
return .{offset = OAllocation.NO_SPACE, metadata = OAllocation.NO_SPACE}; | |
} | |
// Round up to bin index to ensure that alloc >= bin | |
// Gives us min bin index that fits the size | |
minBinIndex := OSmallFloat.uintToFloatRoundUp(size); | |
minTopBinIndex := minBinIndex >> TOP_BINS_INDEX_SHIFT; | |
minLeafBinIndex := minBinIndex & LEAF_BINS_INDEX_MASK; | |
topBinIndex := minTopBinIndex; | |
leafBinIndex := OAllocation.NO_SPACE; | |
// If top bin exists, scan its leaf bin. This can fail (NO_SPACE). | |
if (m_usedBinsTop & (1 << topBinIndex)) { | |
leafBinIndex = findLowestSetBitAfter(m_usedBins[topBinIndex], minLeafBinIndex); | |
} | |
// If we didn't find space in top bin, we search top bin from +1 | |
if (leafBinIndex == OAllocation.NO_SPACE) { | |
topBinIndex = findLowestSetBitAfter(m_usedBinsTop, minTopBinIndex + 1); | |
// Out of space? | |
if (topBinIndex == OAllocation.NO_SPACE) { | |
return .{offset = OAllocation.NO_SPACE, metadata = OAllocation.NO_SPACE}; | |
} | |
// All leaf bins here fit the alloc, since the top bin was rounded up. Start leaf search from bit 0. | |
// NOTE: This search can't fail since at least one leaf bit was set because the top bit was set. | |
leafBinIndex = tzcnt_nonzero(m_usedBins[topBinIndex]); | |
} | |
binIndex := (topBinIndex << TOP_BINS_INDEX_SHIFT) | leafBinIndex; | |
// Pop the top node of the bin. Bin top = node.next. | |
nodeIndex := m_binIndices[binIndex]; | |
node := *m_nodes[nodeIndex]; | |
nodeTotalSize := node.dataSize; | |
node.dataSize = size; | |
node.used = true; | |
m_binIndices[binIndex] = node.binListNext; | |
if (node.binListNext != Node.unused) { | |
m_nodes[node.binListNext].binListPrev = Node.unused; | |
} | |
m_freeStorage -= nodeTotalSize; | |
#if DEBUG_VERBOSE { | |
print("Free storage: % (-%) (allocate)\n", m_freeStorage, nodeTotalSize); | |
} | |
// Bin empty? | |
if (m_binIndices[binIndex] == Node.unused) { | |
// Remove a leaf bin mask bit | |
m_usedBins[topBinIndex] &= ~((1).(u8) << leafBinIndex); | |
// All leaf bins empty? | |
if (m_usedBins[topBinIndex] == 0) { | |
// Remove a top bin mask bit | |
m_usedBinsTop &= ~((1).(u32) << topBinIndex); | |
} | |
} | |
// Push back reminder N elements to a lower bin | |
reminderSize := nodeTotalSize - size; | |
if (reminderSize > 0) { | |
newNodeIndex := insertNodeIntoBin(this, reminderSize, node.dataOffset + size); | |
// Link nodes next to each other so that we can merge them later if both are free | |
// And update the old next neighbor to point to the new node (in middle) | |
if (node.neighborNext != Node.unused) { | |
m_nodes[node.neighborNext].neighborPrev = newNodeIndex; | |
} | |
m_nodes[newNodeIndex].neighborPrev = nodeIndex; | |
m_nodes[newNodeIndex].neighborNext = node.neighborNext; | |
node.neighborNext = newNodeIndex; | |
} | |
return .{offset = node.dataOffset, metadata = nodeIndex}; | |
} | |
oalloc_free :: (using this: *OAllocator, allocation: OAllocation) { | |
assert(allocation.metadata != OAllocation.NO_SPACE); | |
if (!m_nodes) return; | |
nodeIndex := allocation.metadata; | |
node := *m_nodes[nodeIndex]; | |
// Double delete check | |
assert(node.used == true); | |
// Merge with neighbors... | |
offset := node.dataOffset; | |
size := node.dataSize; | |
if ((node.neighborPrev != Node.unused) && (m_nodes[node.neighborPrev].used == false)) { | |
// Previous (contiguous) free node: Change offset to previous node offset. Sum sizes | |
prevNode := *m_nodes[node.neighborPrev]; | |
offset = prevNode.dataOffset; | |
size += prevNode.dataSize; | |
// Remove node from the bin linked list and put it in the freelist | |
removeNodeFromBin(this, node.neighborPrev); | |
assert(prevNode.neighborNext == nodeIndex); | |
node.neighborPrev = prevNode.neighborPrev; | |
} | |
if ((node.neighborNext != Node.unused) && (m_nodes[node.neighborNext].used == false)) { | |
// Next (contiguous) free node: Offset remains the same. Sum sizes. | |
nextNode := *m_nodes[node.neighborNext]; | |
size += nextNode.dataSize; | |
// Remove node from the bin linked list and put it in the freelist | |
removeNodeFromBin(this, node.neighborNext); | |
assert(nextNode.neighborPrev == nodeIndex); | |
node.neighborNext = nextNode.neighborNext; | |
} | |
neighborNext := node.neighborNext; | |
neighborPrev := node.neighborPrev; | |
// Insert the removed node to freelist | |
#if DEBUG_VERBOSE { | |
print("Putting node % into freelist[%] (free)\n", nodeIndex, m_freeOffset + 1); | |
} | |
m_freeOffset += 1; | |
m_freeNodes[m_freeOffset] = nodeIndex; | |
// Insert the (combined) free node to bin | |
combinedNodeIndex := insertNodeIntoBin(this, size, offset); | |
// Connect neighbors with the new combined node | |
if (neighborNext != Node.unused) { | |
m_nodes[combinedNodeIndex].neighborNext = neighborNext; | |
m_nodes[neighborNext].neighborPrev = combinedNodeIndex; | |
} | |
if (neighborPrev != Node.unused) { | |
m_nodes[combinedNodeIndex].neighborPrev = neighborPrev; | |
m_nodes[neighborPrev].neighborNext = combinedNodeIndex; | |
} | |
} | |
oalloc_size :: (using this: OAllocator, allocation: OAllocation) -> u32 { | |
if (allocation.metadata == OAllocation.NO_SPACE) return 0; | |
if (!m_nodes) return 0; | |
return m_nodes[allocation.metadata].dataSize; | |
} | |
oalloc_report :: (using this: OAllocator) -> OStorageReport { | |
largestFreeRegion :u32= 0; | |
freeStorage :u32= 0; | |
// Out of allocations? -> Zero free space | |
if (m_freeOffset > 0) { | |
freeStorage = m_freeStorage; | |
if (m_usedBinsTop) { | |
topBinIndex := (31).(u32) - lzcnt_nonzero(m_usedBinsTop); | |
leafBinIndex := (31).(u32) - lzcnt_nonzero(m_usedBins[topBinIndex]); | |
largestFreeRegion = OSmallFloat.floatToUint((topBinIndex << TOP_BINS_INDEX_SHIFT) | leafBinIndex); | |
assert(freeStorage >= largestFreeRegion); | |
} | |
} | |
return .{totalFreeSpace = freeStorage, largestFreeRegion = largestFreeRegion}; | |
} | |
oalloc_report_full :: (using this: OAllocator) -> OStorageReportFull { | |
report: OStorageReportFull; | |
for m_binIndices { | |
nodeIndex := it; | |
count :u32= 0; | |
while nodeIndex != Node.unused { | |
nodeIndex = m_nodes[nodeIndex].binListNext; | |
count+=1; | |
} | |
report.freeRegions[it_index] = .{size = OSmallFloat.floatToUint(i), count = count }; | |
} | |
return report; | |
} | |
OSmallFloat :: struct { | |
MANTISSA_BITS :u32: 3; | |
MANTISSA_VALUE :u32: 1 << MANTISSA_BITS; | |
MANTISSA_MASK :u32: MANTISSA_VALUE - 1; | |
// Bin sizes follow floating point (exponent + mantissa) distribution (piecewise linear log approx) | |
// This ensures that for each size class, the average overhead percentage stays the same | |
uintToFloatRoundUp :: (size: u32) -> u32 { | |
exp :u32= 0; | |
mantissa :u32= 0; | |
if (size < MANTISSA_VALUE) { | |
// Denorm: 0..(MANTISSA_VALUE-1) | |
mantissa = size; | |
} else { | |
// Normalized: Hidden high bit always 1. Not stored. Just like float. | |
leadingZeros := lzcnt_nonzero(size); | |
highestSetBit := 31 - leadingZeros; | |
mantissaStartBit := highestSetBit - MANTISSA_BITS; | |
exp = mantissaStartBit + 1; | |
mantissa = (size >> mantissaStartBit) & MANTISSA_MASK; | |
lowBitsMask := ((1).(u32) << mantissaStartBit) - 1; | |
// Round up! | |
if ((size & lowBitsMask) != 0) then mantissa+=1; | |
} | |
return (exp << MANTISSA_BITS) + mantissa; // + allows mantissa->exp overflow for round up | |
} | |
uintToFloatRoundDown :: (size: u32) -> u32 { | |
exp :u32= 0; | |
mantissa :u32= 0; | |
if (size < MANTISSA_VALUE) { | |
// Denorm: 0..(MANTISSA_VALUE-1) | |
mantissa = size; | |
} else { | |
// Normalized: Hidden high bit always 1. Not stored. Just like float. | |
leadingZeros := lzcnt_nonzero(size); | |
highestSetBit := 31 - leadingZeros; | |
mantissaStartBit := highestSetBit - MANTISSA_BITS; | |
exp = mantissaStartBit + 1; | |
mantissa = (size >> mantissaStartBit) & MANTISSA_MASK; | |
} | |
return (exp << MANTISSA_BITS) | mantissa; | |
} | |
floatToUint :: (floatValue: u32) -> u32 { | |
exponent := floatValue >> MANTISSA_BITS; | |
mantissa := floatValue & MANTISSA_MASK; | |
if (exponent == 0) { | |
// Denorms | |
return mantissa; | |
} else { | |
return (mantissa | MANTISSA_VALUE) << (exponent - 1); | |
} | |
} | |
} | |
#scope_file | |
#import "Basic"; | |
// 16 bit offsets mode will halve the metadata storage cost | |
// But it only supports up to 65536 maximum allocation count | |
#if USE_16_BIT_NODE_INDICES { | |
NodeIndex :: u16; | |
} else { | |
NodeIndex :: u32; | |
} | |
NUM_TOP_BINS :u32: 32; | |
BINS_PER_LEAF :u32: 8; | |
TOP_BINS_INDEX_SHIFT :u32: 3; | |
LEAF_BINS_INDEX_MASK :u32: 0x7; | |
NUM_LEAF_BINS :u32: NUM_TOP_BINS * BINS_PER_LEAF; | |
pop_u32 :: (_x: u32, $use_asm := true) -> u32 #expand { | |
#if use_asm && CPU == .X64 { | |
result: u32; | |
#asm {popcnt.d result, _x;} | |
return result; | |
} else { | |
x := _x; | |
x = x - ((x >> 1) & 0x5555_5555); | |
x = (x & 0x3333_3333) + ((x >> 2) & 0x3333_3333); | |
x = (x + (x >> 4)) & 0x0f0f_0f0f; | |
x = x + (x >> 8); | |
x = x + (x >> 16); | |
return x & 0x3f; | |
} | |
} | |
// Utility functions | |
lzcnt_nonzero :: inline (v: u32) -> u32 { | |
x := v; | |
x = x | (x >> 1); | |
x = x | (x >> 2); | |
x = x | (x >> 4); | |
x = x | (x >> 8); | |
x = x | (x >> 16); | |
return pop_u32(~x); | |
} | |
tzcnt_nonzero :: inline (v: u32) -> u32 { | |
// densist lookup, John Reiser | |
s_ntz_table :: u8.[ | |
32, 0, 1, 26, 2, 23, 27, 0, 3, 16, 24, 30, 28, 11, 0, 13, 4, | |
7, 17, 0, 25, 22, 31, 15, 29, 10, 12, 6, 0, 21, 14, 9, 5, 20, 8, 19, 18 | |
]; | |
xi := cast(s32)v; | |
xi = (xi & (-xi)); // Isolate rightmost 1-bit. | |
xi %= 37; | |
return s_ntz_table[xi]; | |
} | |
findLowestSetBitAfter :: (bitMask: u32, startBitIndex: u32) -> u32 { | |
maskBeforeStartIndex := ((1).(u32) << startBitIndex) - 1; | |
maskAfterStartIndex := ~maskBeforeStartIndex; | |
bitsAfter := bitMask & maskAfterStartIndex; | |
if (bitsAfter == 0) return OAllocation.NO_SPACE; | |
return tzcnt_nonzero(bitsAfter); | |
} | |
insertNodeIntoBin :: (using this: *OAllocator, size: u32, dataOffset: u32) -> u32 { | |
// Round down to bin index to ensure that bin >= alloc | |
binIndex := OSmallFloat.uintToFloatRoundDown(size); | |
topBinIndex := binIndex >> TOP_BINS_INDEX_SHIFT; | |
leafBinIndex := binIndex & LEAF_BINS_INDEX_MASK; | |
// Bin was empty before? | |
if (m_binIndices[binIndex] == Node.unused) { | |
// Set bin mask bits | |
m_usedBins[topBinIndex] |= (1).(u8) << leafBinIndex; | |
m_usedBinsTop |= (1).(u32) << topBinIndex; | |
} | |
// Take a freelist node and insert on top of the bin linked list (next = old top) | |
topNodeIndex := m_binIndices[binIndex]; | |
nodeIndex := m_freeNodes[m_freeOffset]; | |
m_freeOffset -= 1; | |
#if DEBUG_VERBOSE { | |
print("Getting node % from freelist[%]\n", nodeIndex, m_freeOffset + 1); | |
} | |
m_nodes[nodeIndex] = .{dataOffset = dataOffset, dataSize = size, binListNext = topNodeIndex}; | |
if (topNodeIndex != Node.unused) { | |
m_nodes[topNodeIndex].binListPrev = nodeIndex; | |
} | |
m_binIndices[binIndex] = nodeIndex; | |
m_freeStorage += size; | |
#if DEBUG_VERBOSE { | |
printf("Free storage: % (+%) (insertNodeIntoBin)\n", m_freeStorage, size); | |
} | |
return nodeIndex; | |
} | |
removeNodeFromBin :: (using this: *OAllocator, nodeIndex: u32) { | |
node := *m_nodes[nodeIndex]; | |
if (node.binListPrev != Node.unused) { | |
// Easy case: We have previous node. Just remove this node from the middle of the list. | |
m_nodes[node.binListPrev].binListNext = node.binListNext; | |
if (node.binListNext != Node.unused) { | |
m_nodes[node.binListNext].binListPrev = node.binListPrev; | |
} | |
} else { | |
// Hard case: We are the first node in a bin. Find the bin. | |
// Round down to bin index to ensure that bin >= alloc | |
binIndex := OSmallFloat.uintToFloatRoundDown(node.dataSize); | |
topBinIndex := binIndex >> TOP_BINS_INDEX_SHIFT; | |
leafBinIndex := binIndex & LEAF_BINS_INDEX_MASK; | |
m_binIndices[binIndex] = node.binListNext; | |
if (node.binListNext != Node.unused) { | |
m_nodes[node.binListNext].binListPrev = Node.unused; | |
} | |
// Bin empty? | |
if (m_binIndices[binIndex] == Node.unused) { | |
// Remove a leaf bin mask bit | |
m_usedBins[topBinIndex] &= ~((1).(u8) << leafBinIndex); | |
// All leaf bins empty? | |
if (m_usedBins[topBinIndex] == 0) { | |
// Remove a top bin mask bit | |
m_usedBinsTop &= ~((1).(u32) << topBinIndex); | |
} | |
} | |
} | |
// Insert the node to freelist | |
#if DEBUG_VERBOSE { | |
print("Putting node % into freelist[%] (removeNodeFromBin)\n", nodeIndex, m_freeOffset + 1); | |
} | |
m_freeOffset += 1; | |
m_freeNodes[m_freeOffset] = nodeIndex; | |
m_freeStorage -= node.dataSize; | |
#if DEBUG_VERBOSE { | |
printf("Free storage: % (-%) (removeNodeFromBin)\n", m_freeStorage, node.dataSize); | |
} | |
} |
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