LLM(Low Level Memory Tracker) 是從 4.18 開始引入的新的內存統計工具，比memreport 統計數據更加詳細精確，但又不會像 MallocProfiler 那樣有很大的本身開銷
通過LLM，可以知道游戲消耗的內存分別來自引擎的哪些模塊，讓開發者可以對內存占用高的模塊進行有針對性優化。
Debug、Development包才會啟用ENABLE_LOW_LEVEL_MEM_TRACKER宏，統計邏輯才會編譯進可執行二進制中，才能使用LLM相關的功能
Shipping包是沒有LLM功能，對於Test包可以#define ALLOW_LOW_LEVEL_MEM_TRACKER_IN_TEST 1來將LLM代碼編譯進包
相關邏輯在UnrealEngine\Engine\Source\Runtime\Core\Public\HAL\LowLevelMemTracker.h、UnrealEngine\Engine\Source\Runtime\Core\Private\HAL\LowLevelMemTracker.cpp文件中
LLM通過插入各種tag來將所有待統計的內存划歸到某個tag下。實現原理是：插入的tag會形成一個tag的棧，將FMalloc分配的內存統計到當前棧頂的tag下。
LLM在最底層hook了FMalloc的每一個統計，如果沒有任何tag在當前棧中，那么所有內存計入在untagged這個tag下。
如果我們在代碼中插入一個基於scoped的tag，就可以把這個scope下的內存計入你的tag下。通過LLm我們不會遺漏任何Fmalloc分配的內存。
此外程序剛初始化的時候，LLM會記錄一個內存，被它估計為可執行程序本身的內存，記在ProgramSize這個tag中。
在RHI中對gpu資源的創建也會被LLM記錄 ，在額外的texture，buffer等標簽下，它們不是FMalloc內存的一部分，是對GPU的內存占用的估算。
LLM目前有兩個Tracker（跟蹤器）：Default Tracker（默認跟蹤器）和Platform Tracker（平台跟蹤器）。它們都有自己的獨立分配映射和標記堆棧。
Default Tracker（ELLMTracker::Default）的級別較高，記錄引擎中FMemory的Malloc函數進行的分配。為 stat LLM和 stat LLMFULL控制台命令提供統計信息。
Platform Tracker（ELLMTracker::Platform）的級別較低，記錄從OS進行的所有分配。例如，它會跟蹤FMemory的Malloc函數進行的內部分配。因此，Default Tracker是Platform Tracker統計信息的子集。
運行開關
在編譯時打開 LLM 后，要想在運行時使用 LLM 的功能，還要加上啟動命令行 -LLM -LLMCSV
-LLM：運行時打開LLM統計 或者通過定義#define LLM_AUTO_ENABLE 1默認打開 注：開了之后會導致fps下降23.7%，對性能影響很大
-LLMCSV：將內存統計信息輸出到CSV 文件中，CSV 文件保存在 Saved\Profiling\LLM 目錄下 注：設置控制台變量LLM.LLMWriteInterval xx，修改寫csv文件的頻率為xx秒，默認5秒寫一行
會得到兩個 csv 文件，一個是 LLM_ 前綴，另一個是 LLMPlatform_前綴，這兩個文件分別由兩個 Tracker 生成，這兩個文件的關注點不同
① LLM 主要關注FMalloc內存的消費者，主要就是引擎內各個部分的內存開銷
② LLMPlatform 只關注系統內存的消費者，主要有幾大類: ProgramSize, FMalloc, LLMOverhead
-LLMTAGSETS=Assets：顯示每個資源分配的統計，不只是有大類別的數據。 注：需打開LLM_ALLOW_ASSETS_TAGS 宏
-LLMTAGSETS=AssetClasses：按UObject類別進行分類統計
注：寫CSV時，如果開啟了-LLMTAGSETS 命令行，CSV 文件可能會錯亂。
因為寫 CSV 文件時預留了第一行標題欄內容的緩沖區，當每個資源或資源類很多，會導致標題欄內容溢出，覆蓋了后面的數據區域，所以這里需要自己按需求修改一下
具體的控制台命令為：LLM.LLMHeaderMaxSize 500000
運行時開關 LLM 的處理見 FLowLevelMemTracker::ProcessCommandLine 函數
在UE4CommandLine.txt文件中添加命令行參數：
../../../MyGame/MyGame.uproject -LLM -LLMCSV
Android需要將該文件push到手機的UE4Game/MyGame/UE4CommandLine.txt
iOS需要將ue4commandline.txt（注：需要全小寫）放在如下目錄中：
從csv生成html圖表
PerfreportTool.exe -csv F:\UAGame\Saved\Profiling\LLM\LLM_Pid23989_2021.03.30-14.14.55.csv -o c:\LLMOutput -reporttype LLM -topng. -graphxml LLMReportGraphs.xml -reportxml LLMReportTypes.xml -nostripevents
PerfreportTool.exe -csv F:\UAGame\Saved\Profiling\LLM\LLMPlatform_Pid23989_2021.03.30-14.14.55.csv -o c:\LLMOutput -reporttype LLM -topng. -graphxml LLMReportGraphs.xml -reportxml LLMReportTypes.xml -nostripevents
生成的html文件如下：
統計項說明
Android
LLM_Pid23989_2021.03.30-14.14.55內容如下：
Untagged,RenderingThread,Audio/AudioMisc,EngineInit,Stats,LoadMapMisc,Audio/AudioMixer,GC,Audio,AsyncLoading,UObject,FileSystem,Materials,Shaders,TextureMetaData,InitUObject,UI,EnginePreInit,Textures,Meshes,SceneRender,RenderTargets,RHIMisc,Meshes/StaticMesh,FName,MaterialInstance,PSO,Particles,Localization,ConfigSystem,TaskGraphMiscTasks,Physics/PhysXAllocator,Physics,AssetRegistry,CsvProfiler,Audio/AudioMixerPlugins,Physics/PhysX,NavigationRecast,EngineMisc,ProgramSize,GenericPlatformMallocCrash,FMallocUnused,TrackedTotal,Total,Untracked,StreamingManager,Lua,Meshes/Landscape,Animation,Meshes/SkeletalMesh,Niagara,MediaStreaming,Meshes/InstancedMesh,Physics/PhysXLandscape,Audio/AudioSynthesis,
。。。 。。。
35.32,6.21,0.02,0.90,21.65,5.05,9.52,0.62,9.55,3.08,105.19,13.72,0.54,19.11,0.65,12.84,42.70,18.71,67.28,31.85,34.72,40.85,0.80,8.79,7.12,0.31,0.15,0.78,36.59,2.80,0.00,6.32,6.71,0.13,0.00,0.00,0.39,0.71,3.78,157.18,3.61,55.31,789.20,830.58,41.44,0.44,28.88,0.03,13.38,12.33,0.00,0.00,0.13,0.00,0.00,
35.32,6.21,0.02,0.90,21.52,5.05,9.52,0.62,9.55,3.08,105.22,13.72,0.54,19.11,0.65,12.84,42.71,18.71,67.28,31.78,34.25,40.85,0.80,8.79,7.12,0.31,0.15,0.78,36.59,2.80,0.00,6.33,6.71,0.13,0.00,0.00,0.39,0.71,3.78,157.18,3.61,56.45,789.74,842.68,52.88,0.44,28.91,0.03,13.38,12.27,0.00,0.00,0.13,0.00,0.00,
35.32,6.21,0.02,0.90,21.65,5.05,9.52,0.62,9.55,3.08,105.22,13.72,0.54,19.11,0.65,12.84,42.74,18.71,67.28,31.89,34.99,40.85,0.80,8.79,7.12,0.31,0.15,0.78,36.59,2.80,0.00,6.34,6.73,0.13,0.00,0.00,0.39,0.71,3.79,157.18,3.61,55.68,790.05,828.77,38.50,0.44,28.94,0.03,13.38,12.37,0.00,0.00,0.13,0.00,0.00,
35.32,6.21,0.02,0.90,21.59,5.05,9.52,0.62,9.55,3.08,105.25,13.72,0.54,19.11,0.65,12.84,42.72,18.71,67.28,31.86,35.13,40.85,0.80,8.79,7.12,0.31,0.15,0.78,36.59,2.80,0.00,6.32,6.71,0.13,0.00,0.00,0.39,0.71,3.81,157.18,3.61,55.56,790.05,841.99,52.15,0.44,28.96,0.03,13.44,12.34,0.00,0.00,0.13,0.00,0.00,
35.32,6.21,0.02,0.90,21.40,5.05,9.52,0.65,9.55,3.08,105.18,13.72,0.54,19.11,0.65,12.84,42.72,18.71,67.28,31.32,35.28,40.85,0.80,8.79,7.12,0.31,0.15,0.78,36.59,2.80,0.00,6.34,6.73,0.13,0.00,0.00,0.39,0.71,3.77,157.18,3.61,54.50,788.20,838.28,50.08,0.44,28.99,0.03,13.26,11.80,0.00,0.00,0.13,0.00,0.00,
35.32,6.21,0.02,0.90,21.84,5.05,9.52,0.65,9.55,3.08,105.18,13.72,0.54,19.11,0.65,12.84,42.74,18.71,67.28,31.59,35.64,40.85,0.80,8.79,7.12,0.31,0.15,0.78,36.59,2.80,0.00,6.34,6.73,0.13,0.00,0.00,0.39,0.71,3.77,157.18,3.61,55.04,789.89,837.26,46.91,0.44,29.02,0.03,13.26,12.07,0.00,0.00,0.13,0.00,0.00,
35.32,6.21,0.02,0.90,22.03,5.05,9.52,0.65,9.55,3.08,105.17,13.72,0.54,19.11,0.65,12.84,42.75,18.71,67.28,31.52,35.90,40.85,0.80,8.79,7.12,0.31,0.15,0.78,36.59,2.80,0.00,6.34,6.73,0.13,0.00,0.00,0.39,0.71,3.74,157.18,3.61,54.95,790.17,831.60,40.49,0.44,29.05,0.03,13.26,11.96,0.00,0.00,0.13,0.00,0.00,
35.32,6.21,0.02,0.90,21.46,5.05,9.52,0.65,9.55,3.08,105.19,13.72,0.54,19.11,0.65,12.84,42.73,18.71,67.28,31.74,35.36,40.85,0.80,8.79,7.12,0.31,0.15,0.78,36.59,2.80,0.00,6.34,6.73,0.13,0.00,0.00,0.39,0.71,3.75,157.18,3.61,55.90,790.32,843.07,53.02,0.44,29.07,0.03,13.31,12.22,0.00,0.00,0.13,0.00,0.00,
35.32,6.21,0.02,0.90,21.46,5.05,9.52,0.65,9.55,3.08,105.22,13.72,0.54,19.11,0.65,12.84,42.74,18.71,67.28,31.82,35.44,40.85,0.80,8.79,7.12,0.31,0.15,0.78,36.59,2.80,0.00,6.34,6.73,0.13,0.00,0.00,0.39,0.71,3.77,157.18,3.61,56.08,790.86,843.15,52.41,0.44,29.23,0.03,13.32,12.30,0.00,0.00,0.13,0.00,0.00,
35.32,6.21,0.02,0.90,21.78,5.05,9.52,0.65,9.55,3.08,105.23,13.72,0.54,19.11,0.65,12.84,42.75,18.71,67.28,31.71,36.19,40.85,0.80,8.79,7.12,0.31,0.15,0.78,36.59,2.80,0.00,6.33,6.72,0.13,0.00,0.00,0.39,0.71,3.77,157.18,3.61,55.50,791.27,842.89,51.62,0.44,29.26,0.03,13.32,12.18,0.00,0.00,0.13,0.00,0.00,
Total（830.58） = TrackedTotal（789.2） + Untracked（41.44）
TrackedTotal（789.2） = Untagged（35.32） + RenderingThread（6.21） + EngineInit（0.9） + Stats（21.65） + LoadMapMisc（5.05） + GC（0.62） + Audio（9.55） + AsyncLoading（3.08） + UObject（105.19） + FileSystem（13.72）+ Materials（0.54）
+ Shaders（19.11） + TextureMetaData（0.65） + InitUObject（12.84） + UI（42.7） + EnginePreInit（18.71） + Textures（67.28） + Meshes（31.85） + SceneRender（34.72） + RenderTargets（40.85） + RHIMisc（0.8） + FName（7.12）
+ MaterialInstance（0.31） + PSO（0.15） + Particles（0.78） + Localization（36.59） + ConfigSystem（2.8） + TaskGraphMiscTasks（0）+ Physics（6.71） + AssetRegistry（0.13） + CsvProfiler（0） + NavigationRecast（0.71）
+ EngineMisc（3.78） + ProgramSize（157.18） + GenericPlatformMallocCrash（3.61） + FMallocUnused（55.31） + StreamingManager（0.44） + Lua（28.88） + Animation（13.38） + Niagara（0） + MediaStreaming（0）
Meshes（31.85） > Meshes/StaticMesh（8.79） + Meshes/Landscape（0.03） + Meshes/InstancedMesh（0.13） + Meshes/SkeletalMesh（12.33）
Physics（6.71） = Physics/PhysXAllocator（6.32） + Physics/PhysX（0.39） + Physics/PhysXLandscape（0）
Audio（9.55） = Audio/AudioMisc（0.02） + Audio/AudioMixer（9.52） + Audio/AudioMixerPlugins（0） + Audio/AudioSynthesis（0）
注1：Audio內存占用，可在DefaultEngine.ini中關閉掉
[Audio] UseAudioMixer=False
注2：帶上-NoAudioMixer命令行參數
LLMPlatform_Pid23989_2021.03.30-14.14.55.csv內容如下：
Untagged,FMalloc,Graphics,ProgramSize,GenericPlatformMallocCrash,TrackedTotal,Total,Untracked,LLMOverhead,OSAvailable,
。。。 。。。
0.00,511.05,115.27,157.18,3.61,918.22,961.69,43.47,131.11,3389.45,
0.00,511.61,115.27,157.18,3.61,907.32,962.20,54.88,119.64,3388.55,
0.00,511.86,115.28,157.18,3.61,920.53,961.36,40.84,132.58,3387.90,
0.00,511.86,115.27,157.18,3.61,907.62,961.63,54.02,119.69,3386.14,
0.00,510.05,115.27,157.18,3.61,905.81,957.96,52.16,119.69,3389.23,
0.00,511.74,115.27,157.18,3.61,907.49,956.95,49.46,119.69,3387.49,
0.00,511.99,115.31,157.18,3.61,919.30,962.82,43.52,131.22,3385.75,
0.00,512.18,115.27,157.18,3.61,907.96,962.80,54.84,119.72,3388.29,
0.00,512.68,115.27,157.18,3.61,908.46,962.87,54.41,119.72,3386.87,
0.00,513.11,115.27,157.18,3.61,908.93,962.64,53.72,119.75,3386.62,
Total（961.69） = TrackedTotal（918.22） + Untracked（43.47）
TrackedTotal（918.22） = Untagged（0.00） + FMalloc（511.05） + Graphics（115.27） + ProgramSize（157.18） + GenericPlatformMallocCrash（3.61） + LLMOverhead（131.11）
IOS
LLM_Pid0_2021.09.27-19.41.13.csv內容如下：
Untagged,Stats,EngineInit,RenderingThread,AsyncLoading,UObject,FileSystem,Materials,Shaders,TextureMetaData,FName,InitUObject,Wwise,EnginePreInit,UI,Textures,Metal Textures,Metal Buffers,SceneRender,RenderTargets,RHIMisc,Meshes/StaticMesh,PSO,MaterialInstance,LoadMapMisc,Particles,GC,Meshes,Localization,ConfigSystem,TaskGraphMiscTasks,Physics/PhysXAllocator,AssetRegistry,CsvProfiler,Physics/PhysX,NavigationRecast,EngineMisc,Physics,ProgramSize,FMallocUnused,TrackedTotal,Total,Untracked,StreamingManager,Meshes/Landscape,Lua,Animation,UI/Font,Meshes/InstancedMesh,Meshes/SkeletalMesh,Audio/AudioSoundWaves,Niagara,MediaStreaming,GCloud,Networking,Textures/MergeTexture,Physics/PhysXLandscape,
。。。 。。。
9.39,12.94,1.13,1.22,4.16,93.28,17.82,0.28,20.41,0.53,11.50,13.35,8.13,2.47,34.46,0.56,0.10,0.12,2.62,0.01,0.65,1.23,14.10,0.29,0.97,2.05,7.74,13.00,12.56,3.55,0.00,25.29,0.89,0.00,0.46,0.07,10.36,25.76,29.87,-42.96,363.24,847.58,484.39,0.28,0.00,47.04,2.11,0.89,0.05,11.73,0.00,0.03,0.00,0.05,0.30,0.00,0.01,
9.39,13.13,1.13,1.22,4.16,93.28,17.82,0.28,20.41,0.53,11.50,13.35,8.13,2.47,34.46,0.56,0.10,0.12,2.62,0.01,0.65,1.24,14.10,0.29,0.97,2.05,7.74,13.01,12.56,3.55,0.00,25.29,0.89,0.00,0.46,0.07,10.36,25.76,29.87,-42.98,363.42,847.71,484.25,0.28,0.00,47.06,2.11,0.89,0.05,11.73,0.00,0.03,0.00,0.05,0.30,0.00,0.01,
9.39,12.88,1.13,1.22,4.16,93.28,17.82,0.28,20.41,0.53,11.50,13.35,8.13,2.47,34.47,0.56,0.10,0.12,2.59,0.01,0.65,1.20,14.10,0.29,0.97,2.05,7.74,12.95,12.56,3.55,0.00,25.29,0.89,0.00,0.46,0.07,10.36,25.75,29.87,-42.92,363.15,847.51,484.38,0.28,0.00,47.08,2.11,0.89,0.05,11.71,0.00,0.03,0.00,0.05,0.30,0.00,0.01,
9.39,13.00,1.13,1.22,4.16,93.28,17.82,0.28,20.41,0.53,11.50,13.35,8.13,2.47,34.47,0.56,0.10,0.12,2.66,0.01,0.65,1.20,14.10,0.29,0.97,2.05,7.74,12.97,12.56,3.55,0.00,25.29,0.89,0.00,0.46,0.07,10.36,25.75,29.87,-43.02,363.27,847.60,484.24,0.28,0.00,47.10,2.11,0.89,0.05,11.72,0.00,0.03,0.00,0.05,0.30,0.00,0.01,
9.39,12.88,1.13,1.22,4.16,93.28,17.82,0.28,20.41,0.53,11.50,13.35,8.13,2.47,34.47,0.56,0.10,0.12,2.62,0.01,0.65,1.24,14.10,0.29,0.97,2.05,7.74,13.01,12.56,3.55,0.00,25.29,0.89,0.00,0.46,0.07,10.36,25.76,29.87,-43.05,363.18,847.52,484.31,0.28,0.00,47.12,2.11,0.89,0.05,11.74,0.00,0.03,0.00,0.05,0.30,0.00,0.01,
9.39,13.10,1.13,1.22,4.17,99.00,17.82,0.28,20.41,0.54,11.50,13.76,8.19,2.48,44.66,0.57,0.10,0.12,2.61,0.01,0.65,1.27,14.10,0.29,0.97,2.05,7.74,13.03,14.75,3.55,0.00,25.29,0.89,0.00,0.46,0.07,10.42,25.75,29.87,-53.73,373.40,858.88,485.47,0.28,0.00,49.14,2.11,0.89,0.05,11.72,0.00,0.03,0.00,0.05,0.30,0.00,0.01,
9.39,13.04,1.13,1.22,4.17,99.02,17.82,0.28,20.41,0.54,11.50,13.76,8.16,2.48,44.67,0.57,0.10,0.12,2.65,0.01,0.65,1.20,14.10,0.29,0.97,2.05,7.74,12.96,14.75,3.55,0.00,25.29,0.89,0.00,0.46,0.07,10.46,25.75,29.87,-53.91,373.50,861.30,487.85,0.28,0.00,49.49,2.11,0.89,0.05,11.72,0.00,0.03,0.00,0.05,0.30,0.00,0.01,
9.39,12.79,1.13,1.22,4.17,99.10,17.82,0.28,20.41,0.54,11.50,13.76,8.13,2.48,44.87,0.57,0.10,0.12,2.65,0.01,0.65,1.27,14.10,0.29,0.97,2.05,7.74,13.04,14.79,3.55,0.00,25.29,0.89,0.00,0.46,0.07,10.50,25.76,29.87,-55.87,373.64,861.69,488.01,0.28,0.00,51.43,2.11,0.89,0.05,11.72,0.00,0.03,0.00,0.05,0.30,0.00,0.01,
9.39,12.98,1.13,1.22,4.17,99.10,17.82,0.28,20.41,0.54,11.50,13.76,8.14,2.48,44.86,0.57,0.10,0.12,2.65,0.01,0.65,1.25,14.10,0.29,0.97,2.05,7.74,13.01,14.79,3.55,0.00,25.29,0.89,0.00,0.46,0.07,10.50,25.76,29.87,-55.93,373.84,861.91,488.08,0.28,0.00,51.52,2.11,0.89,0.05,11.72,0.00,0.03,0.00,0.05,0.30,0.00,0.01,
Total（847.58） = TrackedTotal（363.24） + Untracked（484.39）
TrackedTotal（363.24） = Untagged（9.39） + Stats（12.94） + EngineInit（1.13） + RenderingThread（1.22） + AsyncLoading（4.16） + UObject（93.28） + FileSystem（17.82） + Materials（0.28） + Shaders（20.41） + TextureMetaData（0.53）
+ FName（11.5）+ InitUObject（13.35） + Wwise（8.13） + EnginePreInit（2.47） + UI（34.46） + Textures（0.56） + Metal Textures（0.1） + Metal Buffers（0.12） + SceneRender（2.62） + RenderTargets（0.01） + RHIMisc（0.65） + PSO（14.1）
+ MaterialInstance（0.29）+ LoadMapMisc（0.97）+ Particles（2.05）+ GC（7.74）+ Meshes（13）+ Localization（12.56）+ ConfigSystem（3.55）+ TaskGraphMiscTasks（0）+ AssetRegistry（0.89）+ CsvProfiler（0）+ NavigationRecast（0.07）
+ EngineMisc（10.36） + Physics（25.76） + ProgramSize（29.87） + FMallocUnused（-42.96） + StreamingManager（0.28） + Lua（47.04） + Animation（2.11） + Niagara（0.03） + MediaStreaming（0） + GCloud（0.05） + Networking（0.3）
Meshes（13） = Meshes/StaticMesh（1.23） + Meshes/Landscape（0） + Meshes/InstancedMesh（0.05） + Meshes/SkeletalMesh（11.73）
Physics（25.76） = Physics/PhysXAllocator（25.29） + Physics/PhysX（0.46） + Physics/PhysXLandscape（0.01）
LLMPlatform_Pid0_2021.09.27-19.41.13.csv內容如下：
Virtual Memory,Untagged,FMalloc,Metal Textures,Metal Buffers,Metal Render Targets,ProgramSize,TrackedTotal,Total,Untracked,LLMOverhead,OSAvailable,MMIO,
。。。 。。。
400460.56,1.05,333.55,87.24,17.30,156.70,29.87,800.97,1010.75,209.78,163.04,1088.45,12.22,
400451.62,1.05,333.30,87.24,17.30,156.70,29.87,800.72,1010.55,209.83,163.04,1088.65,12.22,
400450.56,1.05,333.42,87.24,17.30,156.70,29.87,800.84,1010.64,209.80,163.04,1088.56,12.22,
400450.50,1.05,333.30,87.24,17.34,156.70,29.87,800.76,1010.56,209.80,163.04,1088.64,12.22,
400456.47,1.05,343.53,87.82,17.25,156.70,29.87,811.49,1021.92,210.43,163.04,1077.28,12.22,
400458.53,1.05,343.62,87.82,17.34,156.70,29.87,808.43,1021.09,212.67,159.79,1078.11,12.22,
400460.06,1.05,343.77,87.82,17.34,156.70,29.87,808.57,1021.48,212.92,159.79,1077.72,12.22,
400453.75,1.05,343.97,87.82,17.34,156.70,29.87,808.77,1021.70,212.93,159.79,1077.50,12.22,
400454.81,1.05,343.78,87.82,17.30,156.70,29.87,808.54,1021.56,213.03,159.79,1077.64,12.22,
400459.12,1.05,343.66,87.82,17.30,156.70,29.87,808.46,1021.39,212.93,159.81,1077.81,12.22,
400459.06,1.05,344.19,87.82,17.30,156.70,29.87,808.96,1021.91,212.95,159.81,1077.29,12.22,
Total（1010.75） = TrackedTotal（800.97） + Untracked（209.78）
TrackedTotal（800.97） = Untagged（1.05） + FMalloc（333.55） + Metal Textures（87.24） + Metal Buffers（17.3） + Metal Render Targets（156.7） + ProgramSize（29.87） + LLMOverhead（163.04） + MMIO（12.22）
以第1條采集的值為例（單位MB），說明各統計項含義：
Untagged // 未分類的內存，即分配內存時候不在 LLM_SCOPE 宏范圍內
ELLMTag::Untagged（Default Tracker）： 35.32
ELLMTag::Untagged（Platform Tracker）： 0
LLMOverhead // LLM本身消耗的內存
（Default Tracker）： 無
ELLMTag::PlatformOverhead（Platform Tracker）: 119.64
TrackedTotal // 通過調用 LLM OnLowLevelAlloc/OnLowLevelFree 統計到的所有內存 即：LLM跟蹤到的所有內存
ELLMTag::TrackedTotal（Default Tracker）：789.74
ELLMTag::PlatformTrackedTotal（Platform Tracker）：907.32
注：統計到的內存值ELLMTag::PlatformTrackedTotal比ELLMTag::TrackedTotal要大
Total // 總內存
ELLMTag::PlatformTotal（Platform Tracker）：962.2
從操作系統獲得的實際內存，不從llm獲得。在Android上為meminfo中的Private Dirty(Total)，不包含Private Clean和Swap部分
ELLMTag::Total（Default Tracker）：842.68
PlatformTotal - LLMOverhead。即為上面的內存減去 LLM 本身消耗的內存，這個內存值可以認為是在不打開 LLM 功能下的進程內存值
Untracked // 未知的內存分配，即 LLM 無法追蹤的內存，比如第三方庫里的內存分配
ELLMTag::PlatformUntracked（Platform Tracker）： 54.88 // PlatformTotal - PlatformTrackedTotal
ELLMTag::Untracked（Default Tracker）：52.88 // Total - TrackedTotal
FMalloc // 通過FMemory內存分配器分配的內存，也就是一般意義上引擎分配的內存，比如各種UObject，紋理，動畫等占用的內存
（Default Tracker）： 無
ELLMTag::FMalloc（Platform Tracker）: 511.61
FMallocUnused // ELLMTag::FMalloc內存分配器的內存 - 通過FMemory得到的內存。即內存分配器中未使用的內存
ELLMTag::FMallocUnused（Default Tracker）： 56.45
（Platform Tracker）: 無
注：LLM追蹤的內存有2種ELLMAllocType::FMalloc和ELLMAllocType::System
ProgramSize // 程序剛起來時占用的內存（具體時機是初始化某個static FName變量，在進入main函數之前），用來彌補LLM初始化之前沒有跟蹤到的部分
ELLMTag::ProgramSize（Default Tracker）：157.18
ELLMTag::ProgramSizePlatform（Platform Tracker）：157.18
Graphics // 顯存
（Default Tracker）： 無
ELLMTag::GraphicsPlatform（Platform Tracker）: 115.27
GenericPlatformMallocCrash // 預分配的 crash 相關的內存，當 crash 發生時用來替換GMalloc
ELLMTag::GenericPlatformMallocCrash（Default Tracker）：3.61
ELLMTag::GenericPlatformMallocCrashPlatform（Platform Tracker）：3.61
OSAvailable // 系統當前可用的物理內存
（Default Tracker）： 無
ELLMTag::PlatformOSAvailable（Platform Tracker）: 3388.55
OOMBackupPool // Out of memory 備用內存池
ELLMTag::BackupOOMMemoryPool（Default Tracker）：未統計
ELLMTag::BackupOOMMemoryPoolPlatform（Platform Tracker）: 未統計
Default Tracker詳細的統計項
ELLMTag::EngineMisc 3.78 // 在以下函數執行過程中分配的內存
AActor::ProcessEvent
UPackageMapClient::SerializeNewActor
FEngineLoop::Tick
ELLMTag::TaskGraphTasksMisc 0 // FTaskThreadAnyThread::ProcessTasks 函數執行過程中分配的內存
Audio 9.52 // 音頻相關的內存，包括音頻資源，音頻線程中分配的內存，具體還包含以下子類別
ELLMTag::AudioMisc 0.02
ELLMTag::AudioSoundWaves
ELLMTag::AudioMixer 9.52
ELLMTag::AudioPrecache
ELLMTag::AudioDecompress
ELLMTag::AudioRealtimePrecache
ELLMTag::AudioFullDecompress
ELLMTag::AudioVoiceChat
ELLMTag::FName 7.12 // FName占用的內存
ELLMTag::Networking // 網絡相關的內存，包含網絡包處理，連接對象內存等
ELLMTag::Meshes 31.85 // Mesh 的頂點緩存，頂點索引緩存占用的內存，還有以下子類別 注：包括VertexBuffer相關在cpu這邊的內存+估算的gpu內存
ELLMTag::StaticMesh 8.79 // StaticMesh 相關的內存，包含 StaticMesh 資源，StaticMeshComponent
ELLMTag::SkeletalMesh 12.33 // SkeletalMeshComponent, SkinnedMeshComponent, SkeletalMesh內存
ELLMTag::InstancedMesh 0.13 // InstancedStaticMeshComponent, HierarchicalInstancedStaticMeshComponent內存
ELLMTag::Landscape // LandscapeComponent, LandscapeProxy, LandscapeComponentSceneProxy內存
ELLMTag::Stats 21.65 // stat 統計相關的內存占用
ELLMTag::Shaders 19.11 // 各種類型 Shander 的內存占用
ELLMTag::PSO 0.15 // Pipeline State Object 緩存的內存占用
ELLMTag::Textures 67.28 // 紋理相關的內存占用 注：包括texture相關在cpu這邊的內存+估算的gpu內存
ELLMTag::TextureMetaData 0.65 // UTexture2D::Serialize 函數執行過程中分配的內存
ELLMTag::RenderTargets 40.85 // RT 相關的內存，包含在 Viewport 中渲染使用的內存
ELLMTag::SceneRender 34.72 // 場景渲染相關的內存占用，包含 Slate RHI Render 的窗口渲染
ELLMTag::RHIMisc 0.8 // 其它渲染相關的內存占用，如各種渲染狀態，RHI Thread 運行過程中的內存
ELLMTag::AsyncLoading 3.08 // 異步資源加載過程中的內存占用，包含 AsyncLoadingThread, Event Driven Loader
ELLMTag::UObject 105.19 // UObject 占用的內存，包含 UClass 等
ELLMTag::Animation 13.38 // 動畫相關的內存，包含 AnimInstance, AnimSequence, AnimationAsset, AnimBlueprint, MorphTarget
ELLMTag::Materials 0.54 // 材質相關的內存，包含 MaterialInterface, MaterialFunction
ELLMTag::Particles 0.78 // 特效相關的內存，包含 ParticleSystemComponent
ELLMTag::GC 0.62 // GC 過程中的內存，分別為以下兩個函數
CollectGarbageInternal
PerformReachabilityAnalysis
ELLMTag::UI 42.7 // Slate 相關的內存，包含字體，TextureAtlas
ELLMTag::PhysX // PhysX 物理相關的內存
ELLMTag::EnginePreInitMemory 18.71 // FEngineLoop::PreInit 函數執行過程中的內存
ELLMTag::EngineInitMemory 0.9 // FEngineLoop::Init 函數執行過程中的內存
ELLMTag::RenderingThreadMemory 6.21 // 渲染線程(RenderingThreadMain)執行過程中的內存
ELLMTag::LoadMapMisc 5.05 // 地圖加載過程中的內存，分別為以下兩個函數
UEngine::LoadMap
UWorld::UpdateLevelStreaming
ELLMTag::StreamingManager 0.44 // StreamableManager 相關的內存，主要是資源 streaming 函數執行過程中的內存
ELLMTag::FileSystem 13.72 // 文件系統相關的內存，主要是文件讀取時的緩沖區，比如Pak 文件
ELLMTag::Localization 36.59 // 本地化相關的內存
ELLMTag::AssetRegistry 0.13 // AssetRegistryModule 內存
ELLMTag::ConfigSystem 2.8 // 配置文件相關的內存
ELLMTag::InitUObject 12.84 // InitUObject函數執行過程中的內存
ELLMTag::MaterialInstance 0.31 // MaterialInstance, MaterialInstanceDynamic包括材質參數內存占用
ELLMTag::Lua 28.88 // Lua 內存
Windows下特有統計項
ELLMTag::WorkingSetSize // 進程物理內存，可用這個值替代上面的PlatformTotal
ELLMTag::PagefileUsed // 進程虛擬內存
ThreadStack // Windows 線程棧內存
ELLMTag::ThreadStack（Platform Tracker）
ELLMTag::ThreadStackPlatform（Default Tracker）
IOS下特有統計項
Metal Buffers
ELLMTagMetal::Buffers（Platform Tracker） 17.30
ELLMTagMetal::Buffers（Default Tracker） 0.12
Metal Textures
ELLMTagMetal::Textures（Platform Tracker）87.24
ELLMTagMetal::Textures（Default Tracker）0.1
Metal RenderTargets
ELLMTagMetal::RenderTargets（Platform Tracker）156.70
MMIO
ELLMTag::PlatformMMIO（Platform Tracker，mmap / munmap文件映射）12.22
llm stat控制台命令
stat llm // 顯示 Default Tracker 分組的簡要內存統計信息
stat llmfull // 顯示 Default Tracker 分組的所有內存統計信息
注1：默認一個Group最多顯示的行數為25，可通過執行控制台變量stats.MaxPerGroup xx來指定新的最大行數為xx
注2：為了能查看顯示不下的內容，自定義開發了stat scroll控制台命令
stat scroll 1 // 向下滾動1行
stat scroll -1 // 向上滾動1行
stat scroll 999 // 滾動到底部
stat scroll -999 // 滾動到頂部
stat scroll restore //恢復初始
Stat LLMPlatform // 顯示 Platform Tracker 分組的內存統計信息
Stat LLMOverhead // 顯示 LLM 本身使用的內存信息
參考
UE4 Low Level Memory Tracker 使用（知乎）
UE4 Low Level Memory Tracker 使用