reduced memory churn using fixed_xxx containers (#236)

* Added EASTL to help with eliminating memory allocations
* Applied EASTL to eliminate memory allocations, primarily by using `fixed_vector` et al to use stack allocations / inline struct allocations

Reduces memory events in traces by close to a factor of 10 in test scenario (starting editor for project F)

3 files changed, 29 insertions, 19 deletions

diff --git a/src/zenstore/include/zenstore/cache/cachedisklayer.h b/src/zenstore/include/zenstore/cache/cachedisklayer.h
index b0b4f22cb..05400c784 100644
--- a/src/zenstore/include/zenstore/cache/cachedisklayer.h
+++ b/src/zenstore/include/zenstore/cache/cachedisklayer.h
@@ -12,8 +12,9 @@ ZEN_THIRD_PARTY_INCLUDES_START
 #include <tsl/robin_map.h>
 ZEN_THIRD_PARTY_INCLUDES_END
 
+#include <EASTL/string.h>
+#include <EASTL/unordered_map.h>
 #include <filesystem>
-#include <unordered_map>
 
 namespace zen {
 
@@ -169,7 +170,7 @@ public:
 	~ZenCacheDiskLayer();
 
 	struct GetBatchHandle;
-	GetBatchHandle* BeginGetBatch(std::vector<ZenCacheValue>& OutResult);
+	GetBatchHandle* BeginGetBatch(ZenCacheValueVec_t& OutResult);
 	void			EndGetBatch(GetBatchHandle* Batch) noexcept;
 	bool			Get(std::string_view Bucket, const IoHash& HashKey, ZenCacheValue& OutValue);
 	void			Get(std::string_view Bucket, const IoHash& HashKey, GetBatchHandle& BatchHandle);
@@ -216,13 +217,16 @@ public:
 	  */
 	struct CacheBucket : public GcReferencer
 	{
-		CacheBucket(GcManager& Gc, std::atomic_uint64_t& OuterCacheMemoryUsage, std::string BucketName, const BucketConfiguration& Config);
+		CacheBucket(GcManager&				   Gc,
+					std::atomic_uint64_t&	   OuterCacheMemoryUsage,
+					std::string_view		   BucketName,
+					const BucketConfiguration& Config);
 		~CacheBucket();
 
 		bool OpenOrCreate(std::filesystem::path BucketDir, bool AllowCreate = true);
 
 		struct GetBatchHandle;
-		GetBatchHandle* BeginGetBatch(std::vector<ZenCacheValue>& OutResult);
+		GetBatchHandle* BeginGetBatch(ZenCacheValueVec_t& OutResult);
 		void			EndGetBatch(GetBatchHandle* Batch) noexcept;
 		bool			Get(const IoHash& HashKey, ZenCacheValue& OutValue);
 		void			Get(const IoHash& HashKey, GetBatchHandle& BatchHandle);
@@ -486,18 +490,20 @@ private:
 	bool	 StartAsyncMemCacheTrim();
 	void	 MemCacheTrim();
 
-	GcManager&													  m_Gc;
-	JobQueue&													  m_JobQueue;
-	std::filesystem::path										  m_RootDir;
-	Configuration												  m_Configuration;
-	std::atomic_uint64_t										  m_TotalMemCachedSize{};
-	std::atomic_bool											  m_IsMemCacheTrimming = false;
-	std::atomic<GcClock::Tick>									  m_NextAllowedTrimTick;
-	mutable RwLock												  m_Lock;
-	std::unordered_map<std::string, std::unique_ptr<CacheBucket>> m_Buckets;
-	std::vector<std::unique_ptr<CacheBucket>>					  m_DroppedBuckets;
-	uint32_t													  m_UpdateCaptureRefCounter = 0;
-	std::unique_ptr<std::vector<std::string>>					  m_CapturedBuckets;
+	typedef eastl::unordered_map<std::string, std::unique_ptr<CacheBucket>, std::hash<std::string>, std::equal_to<std::string>> BucketMap_t;
+
+	GcManager&								  m_Gc;
+	JobQueue&								  m_JobQueue;
+	std::filesystem::path					  m_RootDir;
+	Configuration							  m_Configuration;
+	std::atomic_uint64_t					  m_TotalMemCachedSize{};
+	std::atomic_bool						  m_IsMemCacheTrimming = false;
+	std::atomic<GcClock::Tick>				  m_NextAllowedTrimTick;
+	mutable RwLock							  m_Lock;
+	BucketMap_t								  m_Buckets;
+	std::vector<std::unique_ptr<CacheBucket>> m_DroppedBuckets;
+	uint32_t								  m_UpdateCaptureRefCounter = 0;
+	std::unique_ptr<std::vector<std::string>> m_CapturedBuckets;
 
 	ZenCacheDiskLayer(const ZenCacheDiskLayer&) = delete;
 	ZenCacheDiskLayer& operator=(const ZenCacheDiskLayer&) = delete;
diff --git a/src/zenstore/include/zenstore/cache/cacheshared.h b/src/zenstore/include/zenstore/cache/cacheshared.h
index 9b45c7b21..521c78bb1 100644
--- a/src/zenstore/include/zenstore/cache/cacheshared.h
+++ b/src/zenstore/include/zenstore/cache/cacheshared.h
@@ -6,6 +6,8 @@
 #include <zencore/iohash.h>
 #include <zenstore/gc.h>
 
+#include <EASTL/fixed_vector.h>
+
 #include <gsl/gsl-lite.hpp>
 #include <unordered_map>
 
@@ -32,6 +34,8 @@ struct ZenCacheValue
 	IoHash	 RawHash = IoHash::Zero;
 };
 
+typedef eastl::fixed_vector<ZenCacheValue, 16> ZenCacheValueVec_t;
+
 struct CacheValueDetails
 {
 	struct ValueDetails
diff --git a/src/zenstore/include/zenstore/cache/structuredcachestore.h b/src/zenstore/include/zenstore/cache/structuredcachestore.h
index 82fec9b0e..5e056cf2d 100644
--- a/src/zenstore/include/zenstore/cache/structuredcachestore.h
+++ b/src/zenstore/include/zenstore/cache/structuredcachestore.h
@@ -86,7 +86,7 @@ public:
 	void			EndPutBatch(PutBatchHandle* Batch) noexcept;
 
 	struct GetBatchHandle;
-	GetBatchHandle* BeginGetBatch(std::vector<ZenCacheValue>& OutResults);
+	GetBatchHandle* BeginGetBatch(ZenCacheValueVec_t& OutResults);
 	void			EndGetBatch(GetBatchHandle* Batch) noexcept;
 
 	bool Get(std::string_view Bucket, const IoHash& HashKey, ZenCacheValue& OutValue);
@@ -220,14 +220,14 @@ public:
 	class GetBatch
 	{
 	public:
-		GetBatch(ZenCacheStore& CacheStore, std::string_view Namespace, std::vector<ZenCacheValue>& OutResult);
+		GetBatch(ZenCacheStore& CacheStore, std::string_view Namespace, ZenCacheValueVec_t& OutResult);
 		~GetBatch();
 
 	private:
 		ZenCacheStore&					   m_CacheStore;
 		ZenCacheNamespace*				   m_Store				  = nullptr;
 		ZenCacheNamespace::GetBatchHandle* m_NamespaceBatchHandle = nullptr;
-		std::vector<ZenCacheValue>&		   Results;
+		ZenCacheValueVec_t&				   Results;
 		friend class ZenCacheStore;
 	};