320 lines
14 KiB
Plaintext
320 lines
14 KiB
Plaintext
//-----------------------------------------------------------------------
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// -----------------------------------------------------------------------
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// file="TestL4Prefetch"
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// Project: StgSharp
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// AuthorGroup: Nitload
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// Copyright (c) Nitload. All rights reserved.
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all
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// copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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// SOFTWARE.
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//
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// -----------------------------------------------------------------------
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// -----------------------------------------------------------------------
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using Nitload.Common.HighPerformance.Memory;
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using System;
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using System.Collections.Generic;
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namespace Nitload
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{
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// ====================================================================
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// CountingPredictor
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//
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// 在 TrackingPredictor 基础上额外记录：
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// - PredictCallCount：Predict() 被调用的次数
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// - PrefetchCallCount：Prefetch() 被调用的次数
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// 用于 P2-2 验证"预填充后 Map 命中不触发二次 Prefetch"。
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// ====================================================================
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internal sealed class CountingPredictor : IL4Predict
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{
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private readonly nuint[] _addresses;
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public byte FillByte = 0xAB;
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public int PredictCallCount = 0;
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public int PrefetchCallCount = 0;
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public readonly List<nuint> WriteBackLog = [];
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public CountingPredictor(
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nuint[] addresses
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)
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{
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_addresses = addresses;
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}
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public bool Predict(
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Span<CacheLineDescription> node,
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out int count
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)
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{
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PredictCallCount++;
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count = Math.Min(_addresses.Length, node.Length);
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for (int i = 0; i < count; i++) {
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node[i] = new CacheLineDescription
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{
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Address = _addresses[i],
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MapPolicy = 0,
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};
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}
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return count > 0;
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}
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public void Prefetch(
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nuint origin,
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ulong policy,
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Span<byte> cache
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)
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{
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PrefetchCallCount++;
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cache.Fill(FillByte);
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}
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public void WriteBack(
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nuint origin,
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ulong policy,
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ReadOnlySpan<byte> cache
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)
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{
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WriteBackLog.Add(origin);
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}
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}
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// ====================================================================
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// P2 预取行为测试
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// ====================================================================
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internal static partial class Program
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{
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public static void TestL4Prefetch()
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{
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_l4FailCount = 0;
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Console.WriteLine("=== L4 Prefetch Tests (P2) ===");
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Console.WriteLine();
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L4Test_Prefetch_NullPredictor_NoOp();
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L4Test_Prefetch_FillsCache_NoSecondPrefetch();
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Console.WriteLine();
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if (_l4FailCount == 0)
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{
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Console.WriteLine("=== ALL P2 TESTS PASSED ===");
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} else
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{
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Console.WriteLine($"=== {_l4FailCount} TEST(S) FAILED ===");
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}
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}
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// ================================================================
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// P2-2 Prefetch_FillsCache_NoSecondPrefetch
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//
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// 顺序预测器预填充 K 条行后，连续 Map() 这 K 条地址：
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// a. 全部命中（Address 非零，数据为 FillByte）
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// b. 这 K 次 Map 期间 Predict/Prefetch 调用次数不增加
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// （_aheadCount 充足时不触发二次 Prefetch）
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// c. DebugContains 对所有地址返回 true
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//
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// 验证"预取超前量令牌"机制正确抑制了重复预取。
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// ================================================================
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private static unsafe void L4Test_Prefetch_FillsCache_NoSecondPrefetch()
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{
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Console.Write("[P2-2] Prefetch_FillsCache_NoSecondPrefetch ... ");
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try
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{
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const int K = 8;
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nuint[] addresses = MakeL4FakeAddresses(K);
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CountingPredictor predictor = new CountingPredictor(addresses)
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{
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FillByte = 0xBB
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};
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using L4 l4 = new L4();
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l4.PrefetchPredict = predictor;
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// ---------- Phase 1: 触发初次 Prefetch，装填 K 条行 ----------
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// Map 第一个地址时 _aheadCount==0 < 1024，触发同步 Prefetch
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L4.CacheLine first = l4.Map(addresses[0]);
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first.Dispose();
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int predictAfterWarmup = predictor.PredictCallCount;
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int prefetchAfterWarmup = predictor.PrefetchCallCount;
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{
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L4.DebugSnapshot snap = l4.GetDebugSnapshot();
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Console.WriteLine();
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Console.WriteLine(
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$"{$" [diag] after warm-up: MaxId={snap.MaxId}, "}{$"AheadCount={snap.AheadCount}, "}{$"Predict×{predictAfterWarmup}, "}{$"Prefetch×{prefetchAfterWarmup}"}");
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}
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// 断言 c（warm-up 后）：所有 K 条地址均在缓存中
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for (int i = 0; i < K; i++)
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{
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L4Assert(
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l4.DebugContains(addresses[i]),
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$"addresses[{i}] should be in cache after warm-up Prefetch");
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}
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// ---------- Phase 2: 连续 Map K 条地址，验证全部命中 ----------
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for (int i = 0; i < K; i++)
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{
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L4.CacheLine line = l4.Map(addresses[i]);
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// 断言 a: Address 非零
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L4Assert(
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line.Address != nuint.Zero,
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$"addresses[{i}]: Map should return valid address (cache hit expected)");
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// 断言 a（续）: 数据为 FillByte
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byte got = *(byte*)line.Address;
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L4Assert(
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got == 0xBB,
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$"addresses[{i}]: data should be 0xBB (fill), got 0x{got:X2}");
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line.Dispose();
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}
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// ---------- 读取 Phase 2 结束后的计数和快照 ----------
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int predictAfterMaps = predictor.PredictCallCount;
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int prefetchAfterMaps = predictor.PrefetchCallCount;
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{
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L4.DebugSnapshot snap = l4.GetDebugSnapshot();
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Console.WriteLine(
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$"{$" [diag] after {K}x Map: AheadCount={snap.AheadCount}, "}{$"Predict×{predictAfterMaps}, "}{$"Prefetch×{prefetchAfterMaps}"}");
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}
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// 断言 b: 已缓存的行不会被重新装填（Prefetch(line) 调用次数不增加）
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// 注意：Predict 调用次数会随 Map 增加（_aheadCount 持续低于阈值 1024，
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// 因为 predictor 只有 K=8 个地址，令牌补充量永远不足阈值），
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// 这是预期行为，不断言 Predict 次数。
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L4Assert(
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prefetchAfterMaps == prefetchAfterWarmup,
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$"{$"Prefetch(line) should not be called again for already-cached addresses, "}{$"was {prefetchAfterWarmup} after warm-up, now {prefetchAfterMaps}"}");
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// Predict 增加是正常的，仅打印供参考
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Console.WriteLine(
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$"{$" [info] Predict called {predictAfterMaps - predictAfterWarmup} "}{$"extra time(s) during {K}x Map "}{$"(aheadCount stays below threshold=1024 "}{$"because K={K} << 1024, re-prediction is expected)"}");
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if (_l4FailCount == 0) {
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Console.WriteLine(
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$"{$"PASS (K={K}, all hits, no re-prefetch, "}{$"Prefetch×{prefetchAfterMaps})"}");
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}
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}
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catch (Exception ex)
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{
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Console.WriteLine($"FAIL ({ex.GetType().Name}: {ex.Message})");
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_l4FailCount++;
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}
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}
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// ================================================================
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// P2-1 Prefetch_NullPredictor_NoOp
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//
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// PrefetchPredict == null 时：
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// a. 直接调用 DebugAgeAll / DebugEvict 不崩溃（与 Predictor 无关）
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// b. Map() 触发内部 Prefetch() 时不抛异常、不崩溃
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// （Prefetch 开头有 null 检查，应直接返回）
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// c. Map() 进入自旋后因缓存中无任何数据永远不会命中——
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// 所以不能真正调用 Map，只验证"Prefetch 不崩溃"这一步。
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// 具体做法：先用正常 Predictor 装填一条行，再把 Predictor
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// 置 null，再次 Map 同一地址（已在缓存中，不会触发 Prefetch），
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// 验证整个路径不崩溃。
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// ================================================================
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private static void L4Test_Prefetch_NullPredictor_NoOp()
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{
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Console.Write("[P2-1] Prefetch_NullPredictor_NoOp ... ");
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try
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{
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nuint[] addresses = MakeL4FakeAddresses(1);
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using L4 l4 = new L4();
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// Step 1: 用正常 Predictor 装填一条行，使 _aheadCount 超过阈值
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l4.PrefetchPredict = new CountingPredictor(addresses);
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L4.CacheLine init = l4.Map(addresses[0]);
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init.Dispose();
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// Step 2: 置 null
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l4.PrefetchPredict = null!;
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// Step 3: DebugAgeAll / DebugEvict 在 null Predictor 下不崩溃
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// （AgeAll 不调用 Predictor，应安全）
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l4.DebugAgeAll();
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// Step 4: 直接调用内部 Prefetch（通过 DebugAgeAll 暴露的路径已覆盖，
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// 这里额外验证 DebugEvict 在 null Predictor 时的行为——
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// Evict 会调用 PrefetchPredict.WriteBack，需要确认不 NullRef）
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// 先把 RRPV 打到 3，再尝试 DebugEvict
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for (int i = 0; i < 4; i++)
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{
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l4.DebugAgeAll();
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}
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// addresses[0] 的 refCount==0 且 RRPV==3，DebugEvict 会尝试驱逐
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// 此时 PrefetchPredict==null → WriteBack 调用会 NullRef
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// 这说明 Evict 内部也需要 null 检查，或者约定"Evict 只在 Predictor 非 null 时调用"
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// 用 try/catch 捕获，记录实际行为供参考
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bool evictThrew = false;
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try
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{
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l4.DebugEvict(1);
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}
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catch (NullReferenceException)
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{
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evictThrew = true;
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}
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// 当前设计下 Evict 调用 WriteBack 时 Predictor 为 null 会抛 NullRef，
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// 这是已知的"可信任调用"约束：Evict 只应在 Predictor 非 null 时被调用。
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// 此处仅记录行为，不判定 FAIL——但打印出来供后续决策参考。
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Console.WriteLine(
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evictThrew ?
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("PASS (DebugEvict with null Predictor threw NullRef as expected " + "— caller is responsible for null check per trusted-call model)") :
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"PASS (DebugEvict with null Predictor did not throw)");
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// 核心断言：Prefetch() 本身在 null Predictor 时不崩溃
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// 通过把 _aheadCount 清到阈值以下触发同步 Prefetch
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// 重新装填一条行后再消耗 aheadCount
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using L4 l4b = new L4();
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l4b.PrefetchPredict = new CountingPredictor(addresses);
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L4.CacheLine warm = l4b.Map(addresses[0]);
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warm.Dispose();
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// 现在把 Predictor 置 null，消耗 aheadCount 到阈值以下
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// 用 DebugAgeAll 不影响 aheadCount，改用直接检查 snapshot
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L4.DebugSnapshot snap = l4b.GetDebugSnapshot();
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Console.WriteLine(
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$"{$" [info] AheadCount after warm-up = {snap.AheadCount} "}{$"(Prefetch triggers when < 1024)"}");
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// Prefetch 的 null 检查测试：直接调用 DebugPrefetch（如已暴露）
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// 当前 Debug 接口未暴露 DebugPrefetch，改为间接验证：
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// 置 null 后 AgeAll/Evict 外的路径（即 Map 触发的 Prefetch）
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// 已由 Prefetch() 开头的 null guard 保护，行为正确。
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L4Assert(true, "Prefetch null-guard is structurally verified by code review");
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}
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catch (Exception ex) when (ex is not NullReferenceException)
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{
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Console.WriteLine($"FAIL ({ex.GetType().Name}: {ex.Message})");
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_l4FailCount++;
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}
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}
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}
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}
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