From e82c7675b451209139ad1d8f75e48da7c951a626 Mon Sep 17 00:00:00 2001
From: Nikolay Zdravkov <unsafeptr@gmail.com>
Date: Wed, 6 May 2026 02:43:00 +0300
Subject: [PATCH] fix: use Stopwatch for ReflectionEmitCachingMemberAccessor
 TTL

---
 .../src/System.Text.Json.csproj               |  1 +
 ...flectionEmitCachingMemberAccessor.Cache.cs | 32 +++++++++----------
 2 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/src/libraries/System.Text.Json/src/System.Text.Json.csproj b/src/libraries/System.Text.Json/src/System.Text.Json.csproj
index 2f1a903683e201..6b79836de8cc60 100644
--- a/src/libraries/System.Text.Json/src/System.Text.Json.csproj
+++ b/src/libraries/System.Text.Json/src/System.Text.Json.csproj
@@ -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'))">
diff --git a/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/ReflectionEmitCachingMemberAccessor.Cache.cs b/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/ReflectionEmitCachingMemberAccessor.Cache.cs
index dc203854c3d858..c924f7de362e68 100644
--- a/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/ReflectionEmitCachingMemberAccessor.Cache.cs
+++ b/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Metadata/ReflectionEmitCachingMemberAccessor.Cache.cs
@@ -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?
@@ -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);
@@ -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 _);
                     }
@@ -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)
                 {