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fix: use Stopwatch for ReflectionEmitCachingMemberAccessor TTL #127844

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fix: use Stopwatch for ReflectionEmitCachingMemberAccessor TTL #127844

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1 change: 1 addition & 0 deletions src/libraries/System.Text.Json/src/System.Text.Json.csproj
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Original file line number Diff line number Diff line change
Expand Up @@ -372,6 +372,7 @@ The System.Text.Json library is built-in as part of the shared framework in .NET
<Compile Include="$(CommonPath)Polyfills\BitConverterPolyfills.cs" Link="Common\Polyfills\BitConverterPolyfills.cs" />
<Compile Include="$(CommonPath)Polyfills\ArrayPolyfills.cs" Link="Common\Polyfills\ArrayPolyfills.cs" />
<Compile Include="$(CommonPath)Polyfills\RuntimeHelpersPolyfills.cs" Link="Common\Polyfills\RuntimeHelpersPolyfills.cs" />
<Compile Include="$(CommonPath)Polyfills\StopwatchPolyfills.cs" Link="Common\Polyfills\StopwatchPolyfills.cs" />
</ItemGroup>

<ItemGroup Condition="'$(TargetFrameworkIdentifier)' != '.NETCoreApp' or $([MSBuild]::VersionLessThan('$(TargetFrameworkVersion)', '9.0'))">
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32 changes: 16 additions & 16 deletions .../src/System/Text/Json/Serialization/Metadata/ReflectionEmitCachingMemberAccessor.Cache.cs
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Expand Up @@ -14,16 +14,16 @@ internal sealed partial class ReflectionEmitCachingMemberAccessor
private sealed class Cache<TKey> where TKey : notnull
{
private int _evictLock;
private long _lastEvictedTicks; // timestamp of latest eviction operation.
private readonly long _evictionIntervalTicks; // min timespan needed to trigger a new evict operation.
private readonly long _slidingExpirationTicks; // max timespan allowed for cache entries to remain inactive.
private long _lastEvictedTimestamp; // Stopwatch timestamp of the latest eviction operation.
private readonly TimeSpan _evictionInterval; // min duration needed to trigger a new evict operation.
private readonly TimeSpan _slidingExpiration; // max duration allowed for cache entries to remain inactive.
private readonly ConcurrentDictionary<TKey, CacheEntry> _cache = new();

public Cache(TimeSpan slidingExpiration, TimeSpan evictionInterval)
{
_slidingExpirationTicks = slidingExpiration.Ticks;
_evictionIntervalTicks = evictionInterval.Ticks;
_lastEvictedTicks = DateTime.UtcNow.Ticks;
_slidingExpiration = slidingExpiration;
_evictionInterval = evictionInterval;
_lastEvictedTimestamp = Stopwatch.GetTimestamp();
}

public TValue GetOrAdd<TValue>(TKey key, Func<TKey, TValue> valueFactory) where TValue : class?
Expand All @@ -36,17 +36,17 @@ public TValue GetOrAdd<TValue>(TKey key, Func<TKey, TValue> valueFactory) where
#else
key => new(valueFactory(key)));
#endif
long utcNowTicks = DateTime.UtcNow.Ticks;
Volatile.Write(ref entry.LastUsedTicks, utcNowTicks);
long nowTimestamp = Stopwatch.GetTimestamp();
Volatile.Write(ref entry.LastUsedTimestamp, nowTimestamp);

if (utcNowTicks - Volatile.Read(ref _lastEvictedTicks) >= _evictionIntervalTicks)
if (Stopwatch.GetElapsedTime(Volatile.Read(ref _lastEvictedTimestamp), nowTimestamp) >= _evictionInterval)
{
if (Interlocked.CompareExchange(ref _evictLock, 1, 0) == 0)
{
if (utcNowTicks - _lastEvictedTicks >= _evictionIntervalTicks)
if (Stopwatch.GetElapsedTime(_lastEvictedTimestamp, nowTimestamp) >= _evictionInterval)
{
EvictStaleCacheEntries(utcNowTicks);
Volatile.Write(ref _lastEvictedTicks, utcNowTicks);
EvictStaleCacheEntries(nowTimestamp);
Volatile.Write(ref _lastEvictedTimestamp, nowTimestamp);
}

Volatile.Write(ref _evictLock, 0);
Expand All @@ -59,14 +59,14 @@ public TValue GetOrAdd<TValue>(TKey key, Func<TKey, TValue> valueFactory) where
public void Clear()
{
_cache.Clear();
_lastEvictedTicks = DateTime.UtcNow.Ticks;
_lastEvictedTimestamp = Stopwatch.GetTimestamp();
}

private void EvictStaleCacheEntries(long utcNowTicks)
private void EvictStaleCacheEntries(long nowTimestamp)
{
foreach (KeyValuePair<TKey, CacheEntry> kvp in _cache)
{
if (utcNowTicks - Volatile.Read(ref kvp.Value.LastUsedTicks) >= _slidingExpirationTicks)
if (Stopwatch.GetElapsedTime(Volatile.Read(ref kvp.Value.LastUsedTimestamp), nowTimestamp) >= _slidingExpiration)
{
_cache.TryRemove(kvp.Key, out _);
}
Expand All @@ -76,7 +76,7 @@ private void EvictStaleCacheEntries(long utcNowTicks)
private sealed class CacheEntry
{
public readonly object? Value;
public long LastUsedTicks;
public long LastUsedTimestamp;

public CacheEntry(object? value)
{
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