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stgsharp/StgSharp.Common/HighPerformance/Memory/L4.Prefetch.cs
T

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C#

//-----------------------------------------------------------------------
// -----------------------------------------------------------------------
// file="L4.Prefetch"
// Project: StgSharp
// AuthorGroup: Nitload
// Copyright (c) Nitload. All rights reserved.
//
// 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.
//
// -----------------------------------------------------------------------
// -----------------------------------------------------------------------
using System.ComponentModel;
using System.Numerics;
namespace StgSharp.HighPerformance.Memory
{
public unsafe partial class L4
{
private partial void Prefetch()
{
if (CurrentPredict is null) {
return;
}
IL4Predict predict = CurrentPredict;
Span<CacheLineDescription> span = new(_prediction, PredictionCount);
PredictResult result = predict.Predict(span, out int actualCount);
_exhausted = (result & PredictResult.Exhausted) != 0;
if (actualCount <= 0)
{
_exhausted = true;
return;
}
int missIndex = 0;
for (int i = 0; i < actualCount; i++)
{
ref CacheLineDescription handle = ref span[i];
nuint address = handle.Address;
if (!_map.TryGet(address, out _))
{
// miss and record
span[missIndex] = handle;
missIndex++;
}
}
// now prefetch the misses
for (int i = 0; i < missIndex; i++)
{
CacheLineMetadata* head;
ref CacheLineDescription pHandle = ref span[i];
nuint address = pHandle.Address;
int index;
if (_map.TryGet(address, out nuint handle))
{
head = (CacheLineMetadata*)handle;
index = (int)(head - _head);
_predictCount[index] = 0; // reset eviction counter
#region update predictor belonging
if (_predictCount[index] > short.MaxValue / 2)
{
int predictCount = Volatile.Read(ref _predictCount[index]);
int mapCount = Volatile.Read(ref _mapCount[index]);
int decrement = (int.Min(predictCount, mapCount) + 1) / 2;
_ = Interlocked.Add(ref _predictCount[index], -decrement);
_ = Interlocked.Add(ref _mapCount[index], -decrement);
}
_predictCount[index]++;
#endregion
continue;
}
int retryCount = 0, remain = missIndex - i;
const int maxRetry = 1024;
while (!_bufferAllocator.TryAlloc(pHandle.Size, out index))
{
remain = Evict(remain);
retryCount++;
if (retryCount > maxRetry) {
throw new OverflowException($"Failed to evict cache line after {maxRetry} retries.");
}
if (retryCount > maxRetry / 2) {
Thread.Sleep(1);
}
}
head = _head + index;
head->Origin = address;
head->CustomizeProfile = pHandle.MapPolicy;
head->RefCount = 0;
_predictCount[index] = 1;
_mapCount[index] = 1;
// pre fetch them here
predict.Prefetch(head->Origin, head->CustomizeProfile, new Span<byte>((byte*)(head->PositionMask + _baseAddress), (int)head->SizeMask));
_ = _map.TryAddOrSet(address, (nuint)head, out _);
}
_ = Interlocked.Add(ref _aheadCount, actualCount);
}
}
}