CacheStrategyLinear.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CacheStrategy.h"
#include <atomic>
 
#if !UE_BUILD_SHIPPING
 
namespace StorageServer
{
    // Use cache storage as arena allocator and store all chunks as they come in. No eviction.
    class FCacheStrategyLinear : public ICacheStrategy
    {
    public:
        FCacheStrategyLinear(TUniquePtr<ICacheJournal>&& InJournal, TUniquePtr<ICacheStorage>&& InStorage, const uint64 AbandonAtInvalidSize, const float FlushInterval, const bool bInvalidate);
        virtual ~FCacheStrategyLinear() override;
 
        void InvalidateAll();
        virtual void Invalidate(const FIoChunkId& ChunkId) override
        {
            Invalidate(ChunkId, true);
        }
 
        virtual bool ReadChunk(const FIoChunkId& RequestChunkId, const uint64 RequestOffset, const uint64 RequestSize, TOptional<FIoBuffer> OptDestination, FIoBuffer& OutBuffer, EStorageServerContentType& ContentType) override;
 
        virtual void CacheChunk(const FIoChunkId& RequestChunkId, const uint64 RequestOffset, const uint64 RequestSize, const FIoBuffer& Buffer, const EStorageServerContentType ContentType, const uint64 ResultModTag) override;
 
    private:
        // Linear cache is implemented as arena allocator
        std::atomic<uint64> CurrentSize; // Current size of arena allocator
        uint64 CurrentInvalidSize; // Amount of bytes with-in arena allocator that are stale
        uint64 AbandonAtInvalidSize; // Consider cache to be a lost cause at this amount of stale data
        FCriticalSection JournalLock;
 
        void Invalidate(const FIoChunkId& ChunkId, bool bShouldLockJournal);
        void SetCounters();
    };
}
 
#endif