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113 lines
4.0 KiB
C#
113 lines
4.0 KiB
C#
// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
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// See the LICENCE file in the repository root for full licence text.
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using System;
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using System.Collections.Concurrent;
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using System.Diagnostics.CodeAnalysis;
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using System.Threading;
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using System.Threading.Tasks;
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using osu.Framework.Extensions.TypeExtensions;
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using osu.Framework.Graphics;
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using osu.Framework.Statistics;
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namespace osu.Game.Database
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{
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/// <summary>
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/// A component which performs lookups (or calculations) and caches the results.
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/// Currently not persisted between game sessions.
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/// </summary>
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public abstract partial class MemoryCachingComponent<TLookup, TValue> : Component
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where TLookup : notnull
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{
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private readonly ConcurrentDictionary<TLookup, TValue?> cache = new ConcurrentDictionary<TLookup, TValue?>();
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private readonly GlobalStatistic<MemoryCachingStatistics> statistics;
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protected virtual bool CacheNullValues => true;
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protected MemoryCachingComponent()
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{
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statistics = GlobalStatistics.Get<MemoryCachingStatistics>(nameof(MemoryCachingComponent<TLookup, TValue>), GetType().ReadableName());
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statistics.Value = new MemoryCachingStatistics();
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}
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/// <summary>
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/// Retrieve the cached value for the given lookup.
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/// </summary>
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/// <param name="lookup">The lookup to retrieve.</param>
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/// <param name="token">An optional <see cref="CancellationToken"/> to cancel the operation.</param>
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protected async Task<TValue?> GetAsync(TLookup lookup, CancellationToken token = default)
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{
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if (CheckExists(lookup, out TValue? existing))
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{
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statistics.Value.HitCount++;
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return existing;
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}
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var computed = await ComputeValueAsync(lookup, token).ConfigureAwait(false);
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statistics.Value.MissCount++;
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if (computed != null || CacheNullValues)
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{
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cache[lookup] = computed;
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statistics.Value.Usage = cache.Count;
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}
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return computed;
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}
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/// <summary>
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/// Invalidate all entries matching a provided predicate.
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/// </summary>
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/// <param name="matchKeyPredicate">The predicate to decide which keys should be invalidated.</param>
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protected void Invalidate(Func<TLookup, bool> matchKeyPredicate)
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{
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foreach (var kvp in cache)
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{
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if (matchKeyPredicate(kvp.Key))
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cache.TryRemove(kvp.Key, out _);
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}
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statistics.Value.Usage = cache.Count;
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}
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protected bool CheckExists(TLookup lookup, [MaybeNullWhen(false)] out TValue value) =>
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cache.TryGetValue(lookup, out value);
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/// <summary>
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/// Called on cache miss to compute the value for the specified lookup.
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/// </summary>
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/// <param name="lookup">The lookup to retrieve.</param>
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/// <param name="token">An optional <see cref="CancellationToken"/> to cancel the operation.</param>
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/// <returns>The computed value.</returns>
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protected abstract Task<TValue?> ComputeValueAsync(TLookup lookup, CancellationToken token = default);
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private class MemoryCachingStatistics
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{
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/// <summary>
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/// Total number of cache hits.
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/// </summary>
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public int HitCount;
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/// <summary>
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/// Total number of cache misses.
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/// </summary>
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public int MissCount;
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/// <summary>
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/// Total number of cached entities.
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/// </summary>
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public int Usage;
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public override string ToString()
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{
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int totalAccesses = HitCount + MissCount;
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double hitRate = totalAccesses == 0 ? 0 : (double)HitCount / totalAccesses;
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return $"i:{Usage} h:{HitCount} m:{MissCount} {hitRate:0%}";
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}
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}
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}
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}
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