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⚡ Bolt: Optimize guest string comparison allocations and lock contention #13

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Merged
manupawickramasinghe merged 1 commit into from
Jul 25, 2026
Merged

⚡ Bolt: Optimize guest string comparison allocations and lock contention #13

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83 changes: 59 additions & 24 deletions src/SharpEmu.Libs/Kernel/KernelMemoryCompatExports.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -5493,21 +5493,38 @@ private static bool TryCompareStrings(CpuContext ctx, ulong left, ulong right, u
}

var max = limit == ulong.MaxValue ? 1_048_576UL : Math.Min(limit, 1_048_576UL);
Span<byte> leftByte = stackalloc byte[1];
Span<byte> rightByte = stackalloc byte[1];
for (ulong i = 0; i < max; i++)
// OPTIMIZATION: Read in chunks to minimize VirtualMemory lookups and lock contention.
const int maxChunkSize = 4096;
Span<byte> leftChunk = stackalloc byte[maxChunkSize];
Span<byte> rightChunk = stackalloc byte[maxChunkSize];
ulong offset = 0;

while (offset < max)
{
if (!TryReadCompat(ctx, left + i, leftByte) ||
!TryReadCompat(ctx, right + i, rightByte))
var currentLeft = left + offset;
var currentRight = right + offset;
var leftRemainingInPage = (int)(maxChunkSize - (currentLeft & (maxChunkSize - 1)));
var rightRemainingInPage = (int)(maxChunkSize - (currentRight & (maxChunkSize - 1)));
var readLength = (int)Math.Min((long)(max - offset), Math.Min(leftRemainingInPage, rightRemainingInPage));
var leftSlice = leftChunk[..readLength];
var rightSlice = rightChunk[..readLength];

if (!TryReadCompat(ctx, currentLeft, leftSlice) ||
!TryReadCompat(ctx, currentRight, rightSlice))
{
return false;
}

compare = leftByte[0] - rightByte[0];
if (compare != 0 || leftByte[0] == 0 || rightByte[0] == 0)
for (int i = 0; i < readLength; i++)
{
return true;
compare = leftSlice[i] - rightSlice[i];
if (compare != 0 || leftSlice[i] == 0 || rightSlice[i] == 0)
{
return true;
}
}

offset += (ulong)readLength;
}

compare = 0;
Expand Down Expand Up @@ -7882,30 +7899,48 @@ private static bool TryCompareStringsCaseInsensitive(
out int compare)
{
compare = 0;
Span<byte> leftBuffer = stackalloc byte[1];
Span<byte> rightBuffer = stackalloc byte[1];
for (ulong index = 0; index < limit; index++)
var max = limit == ulong.MaxValue ? 1_048_576UL : Math.Min(limit, 1_048_576UL);
// OPTIMIZATION: Read in chunks to minimize VirtualMemory lookups and lock contention.
const int maxChunkSize = 4096;
Span<byte> leftChunk = stackalloc byte[maxChunkSize];
Span<byte> rightChunk = stackalloc byte[maxChunkSize];
ulong offset = 0;

while (offset < max)
{
if (!TryReadCompat(ctx, left + index, leftBuffer) ||
!TryReadCompat(ctx, right + index, rightBuffer))
var currentLeft = left + offset;
var currentRight = right + offset;
var leftRemainingInPage = (int)(maxChunkSize - (currentLeft & (maxChunkSize - 1)));
var rightRemainingInPage = (int)(maxChunkSize - (currentRight & (maxChunkSize - 1)));
var readLength = (int)Math.Min((long)(max - offset), Math.Min(leftRemainingInPage, rightRemainingInPage));
var leftSlice = leftChunk[..readLength];
var rightSlice = rightChunk[..readLength];

if (!TryReadCompat(ctx, currentLeft, leftSlice) ||
!TryReadCompat(ctx, currentRight, rightSlice))
{
return false;
}

var leftValue = leftBuffer[0];
var rightValue = rightBuffer[0];
var leftLower = ToAsciiLower(leftValue);
var rightLower = ToAsciiLower(rightValue);
if (leftLower != rightLower)
for (int i = 0; i < readLength; i++)
{
compare = leftLower - rightLower;
return true;
}
var leftValue = leftSlice[i];
var rightValue = rightSlice[i];
var leftLower = ToAsciiLower(leftValue);
var rightLower = ToAsciiLower(rightValue);
if (leftLower != rightLower)
{
compare = leftLower - rightLower;
return true;
}

if (leftValue == 0)
{
return true;
if (leftValue == 0)
{
return true;
}
}

offset += (ulong)readLength;
}

return true;
Expand Down