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Rewrite kernel memory allocator (#3316)

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* Rewrite kernel memory allocator

* Remove unused using

* Adjust private static field naming

* Change UlongBitSize to UInt64BitSize

* Fix unused argument, change argument order to be inline with official code and disable random allocation
This commit is contained in:
gdkchan 2022-06-22 12:28:14 -03:00 • committed by GitHub
parent c881cd2d14
commit f2a41b7a1c
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7 changed files with 676 additions and 480 deletions
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298
Ryujinx.HLE/HOS/Kernel/Memory/KPageBitmap.cs Normal file
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using Ryujinx.Common;
using System;
using System.Numerics;
namespace Ryujinx.HLE.HOS.Kernel.Memory
{
class KPageBitmap
{
private struct RandomNumberGenerator
{
private uint _entropy;
private uint _bitsAvailable;
private void RefreshEntropy()
{
_entropy = 0;
_bitsAvailable = sizeof(uint) * 8;
}
private bool GenerateRandomBit()
{
if (_bitsAvailable == 0)
{
RefreshEntropy();
}
bool bit = (_entropy & 1) != 0;
_entropy >>= 1;
_bitsAvailable--;
return bit;
}
public int SelectRandomBit(ulong bitmap)
{
int selected = 0;
int bitsCount = UInt64BitSize / 2;
ulong mask = (1UL << bitsCount) - 1;
while (bitsCount != 0)
{
ulong low = bitmap & mask;
ulong high = (bitmap >> bitsCount) & mask;
bool chooseLow;
if (high == 0)
{
chooseLow = true;
}
else if (low == 0)
{
chooseLow = false;
}
else
{
chooseLow = GenerateRandomBit();
}
if (chooseLow)
{
bitmap = low;
}
else
{
bitmap = high;
selected += bitsCount;
}
bitsCount /= 2;
mask >>= bitsCount;
}
return selected;
}
}
private const int UInt64BitSize = sizeof(ulong) * 8;
private const int MaxDepth = 4;
private readonly RandomNumberGenerator _rng;
private readonly ArraySegment<ulong>[] _bitStorages;
private int _usedDepths;
public int BitsCount { get; private set; }
public int HighestDepthIndex => _usedDepths - 1;
public KPageBitmap()
{
_rng = new RandomNumberGenerator();
_bitStorages = new ArraySegment<ulong>[MaxDepth];
}
public ArraySegment<ulong> Initialize(ArraySegment<ulong> storage, ulong size)
{
_usedDepths = GetRequiredDepth(size);
for (int depth = HighestDepthIndex; depth >= 0; depth--)
{
_bitStorages[depth] = storage;
size = BitUtils.DivRoundUp(size, UInt64BitSize);
storage = storage.Slice((int)size);
}
return storage;
}
public ulong FindFreeBlock(bool random)
{
ulong offset = 0;
int depth = 0;
if (random)
{
do
{
ulong v = _bitStorages[depth][(int)offset];
if (v == 0)
{
return ulong.MaxValue;
}
offset = offset * UInt64BitSize + (ulong)_rng.SelectRandomBit(v);
}
while (++depth < _usedDepths);
}
else
{
do
{
ulong v = _bitStorages[depth][(int)offset];
if (v == 0)
{
return ulong.MaxValue;
}
offset = offset * UInt64BitSize + (ulong)BitOperations.TrailingZeroCount(v);
}
while (++depth < _usedDepths);
}
return offset;
}
public void SetBit(ulong offset)
{
SetBit(HighestDepthIndex, offset);
BitsCount++;
}
public void ClearBit(ulong offset)
{
ClearBit(HighestDepthIndex, offset);
BitsCount--;
}
public bool ClearRange(ulong offset, int count)
{
int depth = HighestDepthIndex;
var bits = _bitStorages[depth];
int bitInd = (int)(offset / UInt64BitSize);
if (count < UInt64BitSize)
{
int shift = (int)(offset % UInt64BitSize);
ulong mask = ((1UL << count) - 1) << shift;
ulong v = bits[bitInd];
if ((v & mask) != mask)
{
return false;
}
v &= ~mask;
bits[bitInd] = v;
if (v == 0)
{
ClearBit(depth - 1, (ulong)bitInd);
}
}
else
{
int remaining = count;
int i = 0;
do
{
if (bits[bitInd + i++] != ulong.MaxValue)
{
return false;
}
remaining -= UInt64BitSize;
}
while (remaining > 0);
remaining = count;
i = 0;
do
{
bits[bitInd + i] = 0;
ClearBit(depth - 1, (ulong)(bitInd + i));
i++;
remaining -= UInt64BitSize;
}
while (remaining > 0);
}
BitsCount -= count;
return true;
}
private void SetBit(int depth, ulong offset)
{
while (depth >= 0)
{
int ind = (int)(offset / UInt64BitSize);
int which = (int)(offset % UInt64BitSize);
ulong mask = 1UL << which;
ulong v = _bitStorages[depth][ind];
_bitStorages[depth][ind] = v | mask;
if (v != 0)
{
break;
}
offset = (ulong)ind;
depth--;
}
}
private void ClearBit(int depth, ulong offset)
{
while (depth >= 0)
{
int ind = (int)(offset / UInt64BitSize);
int which = (int)(offset % UInt64BitSize);
ulong mask = 1UL << which;
ulong v = _bitStorages[depth][ind];
v &= ~mask;
_bitStorages[depth][ind] = v;
if (v != 0)
{
break;
}
offset = (ulong)ind;
depth--;
}
}
private static int GetRequiredDepth(ulong regionSize)
{
int depth = 0;
do
{
regionSize /= UInt64BitSize;
depth++;
}
while (regionSize != 0);
return depth;
}
public static int CalculateManagementOverheadSize(ulong regionSize)
{
int overheadBits = 0;
for (int depth = GetRequiredDepth(regionSize) - 1; depth >= 0; depth--)
{
regionSize = BitUtils.DivRoundUp(regionSize, UInt64BitSize);
overheadBits += (int)regionSize;
}
return overheadBits * sizeof(ulong);
}
}
}