diff --git a/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializerOptions.Caching.cs b/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializerOptions.Caching.cs
index 24152a5c716aec..7fc4c800e72435 100644
--- a/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializerOptions.Caching.cs
+++ b/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializerOptions.Caching.cs
@@ -163,146 +163,87 @@ public void Clear()
///
/// Defines a cache of CachingContexts; instead of using a ConditionalWeakTable which can be slow to traverse
- /// this approach uses a concurrent dictionary pointing to weak references of .
- /// Relevant caching contexts are looked up using the equality comparison defined by .
+ /// this approach uses a fixed-size array of weak references of that can be looked up lock-free.
+ /// Relevant caching contexts are looked up by linear traversal using the equality comparison defined by
+ /// .
///
internal static class TrackedCachingContexts
{
private const int MaxTrackedContexts = 64;
- private static readonly ConcurrentDictionary> s_cache =
- new(concurrencyLevel: 1, capacity: MaxTrackedContexts, new EqualityComparer());
-
- private const int EvictionCountHistory = 16;
- private static readonly Queue s_recentEvictionCounts = new(EvictionCountHistory);
- private static int s_evictionRunsToSkip;
+ private static readonly WeakReference?[] s_trackedContexts = new WeakReference[MaxTrackedContexts];
public static CachingContext GetOrCreate(JsonSerializerOptions options)
{
Debug.Assert(options.IsReadOnly, "Cannot create caching contexts for mutable JsonSerializerOptions instances");
Debug.Assert(options._typeInfoResolver != null);
- ConcurrentDictionary> cache = s_cache;
-
- if (cache.TryGetValue(options, out WeakReference? wr) && wr.TryGetTarget(out CachingContext? ctx))
+ if (TryGetContext(options, out int firstUnpopulatedIndex, out CachingContext? result))
{
- return ctx;
+ return result;
+ }
+ else if (firstUnpopulatedIndex < 0)
+ {
+ // Cache is full; return a fresh instance.
+ return new CachingContext(options);
}
- lock (cache)
+ lock (s_trackedContexts)
{
- if (cache.TryGetValue(options, out wr))
+ if (TryGetContext(options, out firstUnpopulatedIndex, out result))
{
- if (!wr.TryGetTarget(out ctx))
- {
- // Found a dangling weak reference; replenish with a fresh instance.
- ctx = new CachingContext(options);
- wr.SetTarget(ctx);
- }
-
- return ctx;
+ return result;
}
- if (cache.Count == MaxTrackedContexts)
+ var ctx = new CachingContext(options);
+
+ if (firstUnpopulatedIndex >= 0)
{
- if (!TryEvictDanglingEntries())
+ // Cache has capacity -- store the context in the first available index.
+ ref WeakReference? weakRef = ref s_trackedContexts[firstUnpopulatedIndex];
+
+ if (weakRef is null)
+ {
+ weakRef = new(ctx);
+ }
+ else
{
- // Cache is full; return a fresh instance.
- return new CachingContext(options);
+ Debug.Assert(weakRef.TryGetTarget(out _) is false);
+ weakRef.SetTarget(ctx);
}
}
- Debug.Assert(cache.Count < MaxTrackedContexts);
-
- // Use a defensive copy of the options instance as key to
- // avoid capturing references to any caching contexts.
- var key = new JsonSerializerOptions(options);
- Debug.Assert(key._cachingContext == null);
-
- ctx = new CachingContext(options);
- bool success = cache.TryAdd(key, new WeakReference(ctx));
- Debug.Assert(success);
-
return ctx;
}
}
- public static void Clear()
+ private static bool TryGetContext(
+ JsonSerializerOptions options,
+ out int firstUnpopulatedIndex,
+ [NotNullWhen(true)] out CachingContext? result)
{
- lock (s_cache)
- {
- s_cache.Clear();
- s_recentEvictionCounts.Clear();
- s_evictionRunsToSkip = 0;
- }
- }
-
- private static bool TryEvictDanglingEntries()
- {
- // Worst case scenario, the cache has been filled with permanent entries.
- // Evictions are synchronized and each run is in the order of microseconds,
- // so we want to avoid triggering runs every time an instance is initialized,
- // For this reason we use a backoff strategy to average out the cost of eviction
- // across multiple initializations. The backoff count is determined by the eviction
- // rates of the most recent runs.
-
- Debug.Assert(Monitor.IsEntered(s_cache));
-
- if (s_evictionRunsToSkip > 0)
- {
- --s_evictionRunsToSkip;
- return false;
- }
-
- int currentEvictions = 0;
- foreach (KeyValuePair> kvp in s_cache)
- {
- if (!kvp.Value.TryGetTarget(out _))
- {
- bool result = s_cache.TryRemove(kvp.Key, out _);
- Debug.Assert(result);
- currentEvictions++;
- }
- }
-
- s_evictionRunsToSkip = EstimateEvictionRunsToSkip(currentEvictions);
- return currentEvictions > 0;
+ WeakReference?[] trackedContexts = s_trackedContexts;
- // Estimate the number of eviction runs to skip based on recent eviction rates.
- static int EstimateEvictionRunsToSkip(int latestEvictionCount)
+ firstUnpopulatedIndex = -1;
+ for (int i = 0; i < trackedContexts.Length; i++)
{
- Queue recentEvictionCounts = s_recentEvictionCounts;
+ WeakReference? weakRef = trackedContexts[i];
- if (recentEvictionCounts.Count < EvictionCountHistory - 1)
+ if (weakRef is null || !weakRef.TryGetTarget(out CachingContext? ctx))
{
- // Insufficient data points to determine a skip count.
- recentEvictionCounts.Enqueue(latestEvictionCount);
- return 0;
+ if (firstUnpopulatedIndex < 0)
+ {
+ firstUnpopulatedIndex = i;
+ }
}
- else if (recentEvictionCounts.Count == EvictionCountHistory)
+ else if (AreEquivalentOptions(options, ctx.Options))
{
- recentEvictionCounts.Dequeue();
+ result = ctx;
+ return true;
}
-
- recentEvictionCounts.Enqueue(latestEvictionCount);
-
- // Calculate the total number of eviction in the latest runs
- // - If we have at least one eviction per run, on average,
- // do not skip any future eviction runs.
- // - Otherwise, skip ~the number of runs needed per one eviction.
-
- int totalEvictions = 0;
- foreach (int evictionCount in recentEvictionCounts)
- {
- totalEvictions += evictionCount;
- }
-
- int evictionRunsToSkip =
- totalEvictions >= EvictionCountHistory ? 0 :
- (int)Math.Round((double)EvictionCountHistory / Math.Max(totalEvictions, 1));
-
- Debug.Assert(0 <= evictionRunsToSkip && evictionRunsToSkip <= EvictionCountHistory);
- return evictionRunsToSkip;
}
+
+ result = null;
+ return false;
}
}
@@ -311,99 +252,52 @@ static int EstimateEvictionRunsToSkip(int latestEvictionCount)
/// If two instances are equivalent, they should generate identical metadata caches;
/// the converse however does not necessarily hold.
///
- private sealed class EqualityComparer : IEqualityComparer
+ private static bool AreEquivalentOptions(JsonSerializerOptions left, JsonSerializerOptions right)
{
- public bool Equals(JsonSerializerOptions? left, JsonSerializerOptions? right)
+ Debug.Assert(left != null && right != null);
+
+ return
+ left._dictionaryKeyPolicy == right._dictionaryKeyPolicy &&
+ left._jsonPropertyNamingPolicy == right._jsonPropertyNamingPolicy &&
+ left._readCommentHandling == right._readCommentHandling &&
+ left._referenceHandler == right._referenceHandler &&
+ left._encoder == right._encoder &&
+ left._defaultIgnoreCondition == right._defaultIgnoreCondition &&
+ left._numberHandling == right._numberHandling &&
+ left._unknownTypeHandling == right._unknownTypeHandling &&
+ left._defaultBufferSize == right._defaultBufferSize &&
+ left._maxDepth == right._maxDepth &&
+ left._allowTrailingCommas == right._allowTrailingCommas &&
+ left._ignoreNullValues == right._ignoreNullValues &&
+ left._ignoreReadOnlyProperties == right._ignoreReadOnlyProperties &&
+ left._ignoreReadonlyFields == right._ignoreReadonlyFields &&
+ left._includeFields == right._includeFields &&
+ left._propertyNameCaseInsensitive == right._propertyNameCaseInsensitive &&
+ left._writeIndented == right._writeIndented &&
+ left._typeInfoResolver == right._typeInfoResolver &&
+ CompareLists(left._converters, right._converters);
+
+ static bool CompareLists(ConfigurationList left, ConfigurationList right)
{
- Debug.Assert(left != null && right != null);
-
- return
- left._dictionaryKeyPolicy == right._dictionaryKeyPolicy &&
- left._jsonPropertyNamingPolicy == right._jsonPropertyNamingPolicy &&
- left._readCommentHandling == right._readCommentHandling &&
- left._referenceHandler == right._referenceHandler &&
- left._encoder == right._encoder &&
- left._defaultIgnoreCondition == right._defaultIgnoreCondition &&
- left._numberHandling == right._numberHandling &&
- left._unknownTypeHandling == right._unknownTypeHandling &&
- left._defaultBufferSize == right._defaultBufferSize &&
- left._maxDepth == right._maxDepth &&
- left._allowTrailingCommas == right._allowTrailingCommas &&
- left._ignoreNullValues == right._ignoreNullValues &&
- left._ignoreReadOnlyProperties == right._ignoreReadOnlyProperties &&
- left._ignoreReadonlyFields == right._ignoreReadonlyFields &&
- left._includeFields == right._includeFields &&
- left._propertyNameCaseInsensitive == right._propertyNameCaseInsensitive &&
- left._writeIndented == right._writeIndented &&
- left._typeInfoResolver == right._typeInfoResolver &&
- CompareLists(left._converters, right._converters);
-
- static bool CompareLists(ConfigurationList left, ConfigurationList right)
+ int n;
+ if ((n = left.Count) != right.Count)
{
- int n;
- if ((n = left.Count) != right.Count)
- {
- return false;
- }
-
- for (int i = 0; i < n; i++)
- {
- if (!left[i]!.Equals(right[i]))
- {
- return false;
- }
- }
-
- return true;
+ return false;
}
- }
- public int GetHashCode(JsonSerializerOptions options)
- {
- HashCode hc = default;
-
- hc.Add(options._dictionaryKeyPolicy);
- hc.Add(options._jsonPropertyNamingPolicy);
- hc.Add(options._readCommentHandling);
- hc.Add(options._referenceHandler);
- hc.Add(options._encoder);
- hc.Add(options._defaultIgnoreCondition);
- hc.Add(options._numberHandling);
- hc.Add(options._unknownTypeHandling);
- hc.Add(options._defaultBufferSize);
- hc.Add(options._maxDepth);
- hc.Add(options._allowTrailingCommas);
- hc.Add(options._ignoreNullValues);
- hc.Add(options._ignoreReadOnlyProperties);
- hc.Add(options._ignoreReadonlyFields);
- hc.Add(options._includeFields);
- hc.Add(options._propertyNameCaseInsensitive);
- hc.Add(options._writeIndented);
- hc.Add(options._typeInfoResolver);
- GetHashCode(ref hc, options._converters);
-
- static void GetHashCode(ref HashCode hc, ConfigurationList list)
+ for (int i = 0; i < n; i++)
{
- for (int i = 0; i < list.Count; i++)
+ TValue? leftElem = left[i];
+ TValue? rightElem = right[i];
+ bool areEqual = leftElem is null ? rightElem is null : leftElem.Equals(rightElem);
+ if (!areEqual)
{
- hc.Add(list[i]);
+ return false;
}
}
- return hc.ToHashCode();
- }
-
-#if !NETCOREAPP
- ///
- /// Polyfill for System.HashCode.
- ///
- private struct HashCode
- {
- private int _hashCode;
- public void Add(T? value) => _hashCode = (_hashCode, value).GetHashCode();
- public int ToHashCode() => _hashCode;
+ return true;
}
-#endif
}
}
}
diff --git a/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializerOptionsUpdateHandler.cs b/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializerOptionsUpdateHandler.cs
index 8f7f94140f0c48..53031f1a3c34eb 100644
--- a/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializerOptionsUpdateHandler.cs
+++ b/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonSerializerOptionsUpdateHandler.cs
@@ -23,9 +23,6 @@ public static void ClearCache(Type[]? types)
options.Key.ClearCaches();
}
- // Flush the shared caching contexts
- JsonSerializerOptions.TrackedCachingContexts.Clear();
-
// Flush the dynamic method cache
ReflectionEmitCachingMemberAccessor.Clear();
}
diff --git a/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/CacheTests.cs b/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/CacheTests.cs
index e53b33c3b4dda8..772074b7325d5b 100644
--- a/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/CacheTests.cs
+++ b/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/CacheTests.cs
@@ -257,7 +257,6 @@ static Func CreateCacheCountAccessor()
[ActiveIssue("https://github.com/dotnet/runtime/issues/66232", TargetFrameworkMonikers.NetFramework)]
[ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
- [MemberData(nameof(GetJsonSerializerOptions))]
public static void JsonSerializerOptions_ReuseConverterCaches()
{
// This test uses reflection to:
@@ -269,7 +268,7 @@ public static void JsonSerializerOptions_ReuseConverterCaches()
RemoteExecutor.Invoke(static () =>
{
Func getCacheOptions = CreateCacheOptionsAccessor();
- IEqualityComparer equalityComparer = CreateEqualityComparerAccessor();
+ Func equalityComparer = CreateEqualityComparerAccessor();
foreach (var args in GetJsonSerializerOptions())
{
@@ -280,8 +279,7 @@ public static void JsonSerializerOptions_ReuseConverterCaches()
JsonSerializerOptions originalCacheOptions = getCacheOptions(options);
Assert.NotNull(originalCacheOptions);
- Assert.True(equalityComparer.Equals(options, originalCacheOptions));
- Assert.Equal(equalityComparer.GetHashCode(options), equalityComparer.GetHashCode(originalCacheOptions));
+ Assert.True(equalityComparer(options, originalCacheOptions));
for (int i = 0; i < 5; i++)
{
@@ -290,8 +288,7 @@ public static void JsonSerializerOptions_ReuseConverterCaches()
JsonSerializer.Serialize(42, options2);
- Assert.True(equalityComparer.Equals(options2, originalCacheOptions));
- Assert.Equal(equalityComparer.GetHashCode(options2), equalityComparer.GetHashCode(originalCacheOptions));
+ Assert.True(equalityComparer(options2, originalCacheOptions));
Assert.Same(originalCacheOptions, getCacheOptions(options2));
}
}
@@ -327,7 +324,7 @@ public static void JsonSerializerOptions_EqualityComparer_ChangingAnySettingShou
// - All public setters in JsonSerializerOptions
//
// If either of them changes, this test will need to be kept in sync.
- IEqualityComparer equalityComparer = CreateEqualityComparerAccessor();
+ Func equalityComparer = CreateEqualityComparerAccessor();
(PropertyInfo prop, object value)[] propertySettersAndValues = GetPropertiesWithSettersAndNonDefaultValues().ToArray();
@@ -337,19 +334,16 @@ public static void JsonSerializerOptions_EqualityComparer_ChangingAnySettingShou
Assert.Fail($"{nameof(GetPropertiesWithSettersAndNonDefaultValues)} missing property declaration for {prop.Name}, please update the method.");
}
- Assert.True(equalityComparer.Equals(JsonSerializerOptions.Default, JsonSerializerOptions.Default));
- Assert.Equal(equalityComparer.GetHashCode(JsonSerializerOptions.Default), equalityComparer.GetHashCode(JsonSerializerOptions.Default));
+ Assert.True(equalityComparer(JsonSerializerOptions.Default, JsonSerializerOptions.Default));
foreach ((PropertyInfo prop, object? value) in propertySettersAndValues)
{
var options = new JsonSerializerOptions();
prop.SetValue(options, value);
- Assert.True(equalityComparer.Equals(options, options));
- Assert.Equal(equalityComparer.GetHashCode(options), equalityComparer.GetHashCode(options));
+ Assert.True(equalityComparer(options, options));
- Assert.False(equalityComparer.Equals(JsonSerializerOptions.Default, options));
- Assert.NotEqual(equalityComparer.GetHashCode(JsonSerializerOptions.Default), equalityComparer.GetHashCode(options));
+ Assert.False(equalityComparer(JsonSerializerOptions.Default, options));
}
static IEnumerable<(PropertyInfo, object)> GetPropertiesWithSettersAndNonDefaultValues()
@@ -395,16 +389,14 @@ public static void JsonSerializerOptions_EqualityComparer_ApplyingJsonSerializer
//
// If either of them changes, this test will need to be kept in sync.
- IEqualityComparer equalityComparer = CreateEqualityComparerAccessor();
+ Func equalityComparer = CreateEqualityComparerAccessor();
var options1 = new JsonSerializerOptions { WriteIndented = true };
var options2 = new JsonSerializerOptions { WriteIndented = true };
- Assert.True(equalityComparer.Equals(options1, options2));
- Assert.Equal(equalityComparer.GetHashCode(options1), equalityComparer.GetHashCode(options2));
+ Assert.True(equalityComparer(options1, options2));
_ = new MyJsonContext(options1); // Associate copy with a JsonSerializerContext
- Assert.False(equalityComparer.Equals(options1, options2));
- Assert.NotEqual(equalityComparer.GetHashCode(options1), equalityComparer.GetHashCode(options2));
+ Assert.False(equalityComparer(options1, options2));
}
private class MyJsonContext : JsonSerializerContext
@@ -416,11 +408,10 @@ public MyJsonContext(JsonSerializerOptions options) : base(options) { }
protected override JsonSerializerOptions? GeneratedSerializerOptions => Options;
}
- public static IEqualityComparer CreateEqualityComparerAccessor()
+ public static Func CreateEqualityComparerAccessor()
{
- Type equalityComparerType = typeof(JsonSerializerOptions).GetNestedType("EqualityComparer", BindingFlags.NonPublic);
- Assert.NotNull(equalityComparerType);
- return (IEqualityComparer)Activator.CreateInstance(equalityComparerType, nonPublic: true);
+ MethodInfo equalityComparerMethod = typeof(JsonSerializerOptions).GetMethod("AreEquivalentOptions", BindingFlags.NonPublic | BindingFlags.Static);
+ return (Func)Delegate.CreateDelegate(typeof(Func), equalityComparerMethod);
}
public static IEnumerable WriteSuccessCases