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[GPU] Stop reading ahead windows whose copies keep going stale

This commit is contained in:
ParantezTech 2026-10-11 01:37:03 +03:00
parent b5c15a7426
commit d2090f47fb
1 changed files with 56 additions and 7 deletions
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63
src/SharpEmu.Libs/Gpu/Buffers/GuestBufferCache.cs
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@ -1003,6 +1003,8 @@ public sealed unsafe class GuestBufferCache : IGuestBufferStore, IDisposable
private const long HotWindowLifetime = 512;
private const int MaxEagerReadbacks = 4;
private const int MaxAsyncReadbackAttempts = 4;
private const int EagerStrikeLimit = 3;
private const long EagerMuteBatches = 4096;
private readonly Dictionary<ulong, HotWindow> _hotWindows = new();
private readonly HashSet<ulong> _eagerCandidates = new();
private readonly List<PendingDownload> _eagerDownloads = new();
@ -1010,8 +1012,9 @@ public sealed unsafe class GuestBufferCache : IGuestBufferStore, IDisposable
private static long _reportedEagerStarted;
private static long _reportedEagerUsed;
private static long _reportedEagerStale;
private static long _reportedEagerMuted;
private readonly record struct HotWindow(ulong Address, ulong Size, long LastHit);
private readonly record struct HotWindow(ulong Address, ulong Size, long LastHit, int Strikes = 0, long MutedUntil = 0);
internal long EagerReadbacksStarted { get; private set; }
@ -1019,7 +1022,44 @@ public sealed unsafe class GuestBufferCache : IGuestBufferStore, IDisposable
private void NoteHotReadback(ulong guestAddress, ulong size)
{
_hotWindows[guestAddress & ~(ReadbackWindowBytes - 1)] = new HotWindow(guestAddress, size, _batchSerial);
var key = guestAddress & ~(ReadbackWindowBytes - 1);
_hotWindows[key] = _hotWindows.TryGetValue(key, out var hot)
? hot with { Address = guestAddress, Size = size, LastHit = _batchSerial }
: new HotWindow(guestAddress, size, _batchSerial);
}
internal long EagerReadbacksWasted { get; private set; }
private void NoteEagerOutcome(ulong key, bool wasted)
{
if (wasted)
{
EagerReadbacksWasted++;
}
if (!_hotWindows.TryGetValue(key, out var hot))
{
return;
}
if (!wasted)
{
if (hot.Strikes != 0)
{
_hotWindows[key] = hot with { Strikes = 0 };
}
return;
}
var strikes = hot.Strikes + 1;
_hotWindows[key] = strikes >= EagerStrikeLimit
? hot with { Strikes = 0, MutedUntil = _batchSerial + EagerMuteBatches }
: hot with { Strikes = strikes };
if (strikes >= EagerStrikeLimit)
{
Interlocked.Increment(ref _reportedEagerMuted);
}
}
private void NoteHotWindowWrite(ulong guestAddress, ulong size)
@ -1032,10 +1072,11 @@ public sealed unsafe class GuestBufferCache : IGuestBufferStore, IDisposable
var last = (guestAddress + size - 1) & ~(ReadbackWindowBytes - 1);
for (var key = guestAddress & ~(ReadbackWindowBytes - 1); key <= last; key += ReadbackWindowBytes)
{
if (_hotWindows.TryGetValue(key, out var hot) && _batchSerial - hot.LastHit <= HotWindowLifetime)
if (_hotWindows.TryGetValue(key, out var hot) && _batchSerial - hot.LastHit <= HotWindowLifetime &&
_batchSerial >= hot.MutedUntil)
{
_eagerCandidates.Add(key);
HotWritePending = true;
HotWritePending |= hot.Strikes == 0;
}
}
}
@ -1063,7 +1104,8 @@ public sealed unsafe class GuestBufferCache : IGuestBufferStore, IDisposable
if ((_batchSerial & 1023) == 0)
{
foreach (var key in _hotWindows.Where(pair => _batchSerial - pair.Value.LastHit > HotWindowLifetime).Select(pair => pair.Key).ToList())
foreach (var key in _hotWindows.Where(pair => _batchSerial - pair.Value.LastHit > HotWindowLifetime && _batchSerial >= pair.Value.MutedUntil)
.Select(pair => pair.Key).ToList())
{
_hotWindows.Remove(key);
}
@ -1083,7 +1125,7 @@ public sealed unsafe class GuestBufferCache : IGuestBufferStore, IDisposable
}
if (!_hotWindows.TryGetValue(key, out var hot) || _batchSerial - hot.LastHit > HotWindowLifetime ||
StartEagerReadback(hot) != EagerStart.Deferred)
_batchSerial < hot.MutedUntil || StartEagerReadback(hot) != EagerStart.Deferred)
{
(settled ??= []).Add(key);
}
@ -1137,6 +1179,7 @@ public sealed unsafe class GuestBufferCache : IGuestBufferStore, IDisposable
_eagerDownloads.Add(new PendingDownload
{
HotKey = hot.Address & ~(ReadbackWindowBytes - 1),
Ticket = ticket,
Copies = copies,
WriteTicks = writeTicks,
@ -1245,7 +1288,7 @@ public sealed unsafe class GuestBufferCache : IGuestBufferStore, IDisposable
internal long StalePiecesKept { get; private set; }
public static string TakeAsyncReadbackReport() => FormattableString.Invariant(
$"[PERF][ASYNC_READBACK] applied={Interlocked.Exchange(ref _reportedApplied, 0)} retried={Interlocked.Exchange(ref _reportedRetried, 0)} published_pieces={Interlocked.Exchange(ref _reportedPublishedPieces, 0)} stale_pieces={Interlocked.Exchange(ref _reportedStalePieces, 0)} eager_started={Interlocked.Exchange(ref _reportedEagerStarted, 0)} eager_used={Interlocked.Exchange(ref _reportedEagerUsed, 0)} eager_stale={Interlocked.Exchange(ref _reportedEagerStale, 0)}");
$"[PERF][ASYNC_READBACK] applied={Interlocked.Exchange(ref _reportedApplied, 0)} retried={Interlocked.Exchange(ref _reportedRetried, 0)} published_pieces={Interlocked.Exchange(ref _reportedPublishedPieces, 0)} stale_pieces={Interlocked.Exchange(ref _reportedStalePieces, 0)} eager_started={Interlocked.Exchange(ref _reportedEagerStarted, 0)} eager_used={Interlocked.Exchange(ref _reportedEagerUsed, 0)} eager_stale={Interlocked.Exchange(ref _reportedEagerStale, 0)} eager_muted={Interlocked.Exchange(ref _reportedEagerMuted, 0)}");
private sealed record PendingDownload
{
@ -1258,6 +1301,7 @@ public sealed unsafe class GuestBufferCache : IGuestBufferStore, IDisposable
public required ulong Size { get; init; }
public required bool IsWrite { get; init; }
public bool Eager { get; init; }
public ulong HotKey { get; init; }
public required GuestMemoryProfile.ReadbackSource Source { get; init; }
public required long Started { get; init; }
}
@ -1369,6 +1413,11 @@ public sealed unsafe class GuestBufferCache : IGuestBufferStore, IDisposable
}
var stale = copies.Count - published;
if (pending.Eager)
{
NoteEagerOutcome(pending.HotKey, stale != 0);
}
if (stale != 0)
{
StalePiecesKept += stale;