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Improve the locking per key logic in the CachingService #187

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Improve the locking per key logic in the CachingService #187

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47 changes: 12 additions & 35 deletions LazyCache/CachingService.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,7 @@ public class CachingService : IAppCache
{
private readonly Lazy<ICacheProvider> cacheProvider;

private readonly int[] keyLocks;
private readonly object[] keyLocks;

public CachingService() : this(DefaultCacheProvider)
{
Expand All @@ -22,16 +22,17 @@ public CachingService(Lazy<ICacheProvider> cacheProvider)
{
this.cacheProvider = cacheProvider ?? throw new ArgumentNullException(nameof(cacheProvider));
var lockCount = Math.Max(Environment.ProcessorCount * 8, 32);
keyLocks = new int[lockCount];
keyLocks = new object[lockCount];
for (i = 0; i < keyLocks.Length; i++) keyLocks[i] = new object();
}

public CachingService(Func<ICacheProvider> cacheProviderFactory)
{
if (cacheProviderFactory == null) throw new ArgumentNullException(nameof(cacheProviderFactory));
cacheProvider = new Lazy<ICacheProvider>(cacheProviderFactory);
var lockCount = Math.Max(Environment.ProcessorCount * 8, 32);
keyLocks = new int[lockCount];

keyLocks = new object[lockCount];
for (i = 0; i < keyLocks.Length; i++) keyLocks[i] = new object();
}

public CachingService(ICacheProvider cache) : this(() => cache)
Expand Down Expand Up @@ -117,16 +118,10 @@ object CacheFactory(ICacheEntry entry) =>

// acquire lock per key
uint hash = (uint)key.GetHashCode() % (uint)keyLocks.Length;
while (Interlocked.CompareExchange(ref keyLocks[hash], 1, 0) == 1) { Thread.Yield(); }

try
lock (keyLocks[hash])
{
cacheItem = CacheProvider.GetOrCreate<object>(key, policy, CacheFactory);
}
finally
{
keyLocks[hash] = 0;
}

try
{
Expand All @@ -139,16 +134,10 @@ object CacheFactory(ICacheEntry entry) =>

// acquire lock again
hash = (uint)key.GetHashCode() % (uint)keyLocks.Length;
while (Interlocked.CompareExchange(ref keyLocks[hash], 1, 0) == 1) { Thread.Yield(); }

try
lock (keyLocks[hash])
{
cacheItem = CacheProvider.GetOrCreate<object>(key, CacheFactory);
}
finally
{
keyLocks[hash] = 0;
}
result = GetValueFromLazy<T>(cacheItem, out _ /* we just evicted so type change cannot happen this time */);
}

Expand Down Expand Up @@ -195,10 +184,6 @@ public virtual async Task<T> GetOrAddAsync<T>(string key, Func<ICacheEntry, Task
// below, and guarded using the async lazy. Here we just ensure only one thread can place
// the AsyncLazy into the cache at one time

// acquire lock
uint hash = (uint)key.GetHashCode() % (uint)keyLocks.Length;
while (Interlocked.CompareExchange(ref keyLocks[hash], 1, 0) == 1) { Thread.Yield(); }

object CacheFactory(ICacheEntry entry) =>
new AsyncLazy<T>(async () =>
{
Expand All @@ -208,14 +193,12 @@ object CacheFactory(ICacheEntry entry) =>
return result;
});

try
// acquire lock
uint hash = (uint)key.GetHashCode() % (uint)keyLocks.Length;
lock (keyLocks[hash])
{
cacheItem = CacheProvider.GetOrCreate<object>(key, policy, CacheFactory);
}
finally
{
keyLocks[hash] = 0;
}

try
{
Expand All @@ -228,16 +211,10 @@ object CacheFactory(ICacheEntry entry) =>

// acquire lock
hash = (uint)key.GetHashCode() % (uint)keyLocks.Length;
while (Interlocked.CompareExchange(ref keyLocks[hash], 1, 0) == 1) { Thread.Yield(); }

try
lock (keyLocks[hash])
{
cacheItem = CacheProvider.GetOrCreate<object>(key, CacheFactory);
}
finally
{
keyLocks[hash] = 0;
}
result = GetValueFromAsyncLazy<T>(cacheItem, out _ /* we just evicted so type change cannot happen this time */);
}

Expand Down Expand Up @@ -341,4 +318,4 @@ protected virtual void ValidateKey(string key)
throw new ArgumentOutOfRangeException(nameof(key), "Cache keys cannot be empty or whitespace");
}
}
}
}