From 0b8c56615de26d705f8786b67e8a826b3e44c5db Mon Sep 17 00:00:00 2001
From: Alastair Crabtree <alastair.crabtree@bbc.com>
Date: Sun, 20 Sep 2020 21:52:20 +0100
Subject: [PATCH] task: change lock count to be 32 based on perf test

test-result on 6 (12 HT) core machine:

# Locks, Cache req in 10s
1        6240625
2        10452129
6        19198527
12       27735172
24       27086363
32       32524781
128      32039528
1024     31144725
8000     33000461
---
 .../CachingServiceMemoryCacheProviderTests.cs | 64 +++++++++++++++++++
 LazyCache/CachingService.cs                   |  2 +-
 2 files changed, 65 insertions(+), 1 deletion(-)

diff --git a/LazyCache.UnitTests/CachingServiceMemoryCacheProviderTests.cs b/LazyCache.UnitTests/CachingServiceMemoryCacheProviderTests.cs
index c353199..ae82190 100644
--- a/LazyCache.UnitTests/CachingServiceMemoryCacheProviderTests.cs
+++ b/LazyCache.UnitTests/CachingServiceMemoryCacheProviderTests.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Threading;
 using System.Threading.Tasks;
 using FluentAssertions;
@@ -909,6 +910,69 @@ public async Task GetOrAddAsyncWithImmediateExpirationDoesExpireItems()
             Assert.That(actual, Is.Null);
         }
 
+        [Test]
+        [Ignore("Not a real unit tests - just used for hammering the cache")]
+        public async Task PerfTest()
+        {
+            var watch = new Stopwatch();
+            watch.Start();
+            var asyncThreads = 10;
+            var syncThreads = 10;
+            var uniqueCacheItems = 20;
+            int cacheMiss = 0;
+            int hits = 0;
+            var cancel = new CancellationTokenSource(TimeSpan.FromSeconds(10));
+
+            async Task<ComplexTestObject> GetStuffAsync()
+            {
+                await Task.Delay(25);
+                Interlocked.Increment(ref cacheMiss);
+                return new ComplexTestObject();
+            }
+
+            ComplexTestObject GetStuff()
+            {
+                Thread.Sleep(25);
+                Interlocked.Increment(ref cacheMiss);
+                return new ComplexTestObject();
+            }
+
+
+            var asyncActions = Task.Run(() =>
+            {
+                Parallel.For(1, asyncThreads, async i =>
+                {
+                    while (!cancel.IsCancellationRequested)
+                    {
+                        var key = $"stuff-{hits % uniqueCacheItems}";
+                        var cached = await sut.GetOrAddAsync(key, () => GetStuffAsync(), DateTimeOffset.UtcNow.AddSeconds(1));
+                        if(!cancel.IsCancellationRequested) Interlocked.Increment(ref hits);
+                    }
+                });
+            });
+
+            var syncActions = Task.Run(() =>
+            {
+                Parallel.For(1, syncThreads, i =>
+                {
+                    while (!cancel.IsCancellationRequested)
+                    {
+                        var key = $"stuff-{hits % uniqueCacheItems}";
+                        var cached = sut.GetOrAdd(key, () => GetStuff(), DateTimeOffset.UtcNow.AddSeconds(1));
+                        if (!cancel.IsCancellationRequested) Interlocked.Increment(ref hits);
+                    }
+                });
+            });
+
+            await Task.WhenAll(asyncActions, syncActions);
+
+            watch.Stop();
+            Console.WriteLine(watch.Elapsed);
+            Console.WriteLine("miss " + cacheMiss);
+            Console.WriteLine("hit " + hits);
+        }
+
+
         [Test]
         public void GetOrAddWithPolicyAndThenGetObjectReturnsCorrectType()
         {
diff --git a/LazyCache/CachingService.cs b/LazyCache/CachingService.cs
index 9107af8..84d5bf8 100644
--- a/LazyCache/CachingService.cs
+++ b/LazyCache/CachingService.cs
@@ -13,7 +13,7 @@ public class CachingService : IAppCache
     {
         private readonly Lazy<ICacheProvider> cacheProvider;
 
-        private readonly int[] keyLocks = new int[8192];
+        private readonly int[] keyLocks = new int[32];
 
         public CachingService() : this(DefaultCacheProvider)
         {