├── .gitattributes ├── .gitignore ├── Homework.sln ├── MemoryExpert-Slides-M08L04-Homework.pdf ├── PagesOfLargeArray ├── App.config ├── PagesOfLargeArray.csproj ├── Program.cs └── Properties │ └── AssemblyInfo.cs └── README.md /.gitattributes: -------------------------------------------------------------------------------- 1 | ############################################################################### 2 | # Set default behavior to automatically normalize line endings. 3 | ############################################################################### 4 | * text=auto 5 | 6 | ############################################################################### 7 | # Set default behavior for command prompt diff. 8 | # 9 | # This is need for earlier builds of msysgit that does not have it on by 10 | # default for csharp files. 11 | # Note: This is only used by command line 12 | ############################################################################### 13 | #*.cs diff=csharp 14 | 15 | ############################################################################### 16 | # Set the merge driver for project and solution files 17 | # 18 | # Merging from the command prompt will add diff markers to the files if there 19 | # are conflicts (Merging from VS is not affected by the settings below, in VS 20 | # the diff markers are never inserted). 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To do so, just uncomment the entries below 24 | ############################################################################### 25 | #*.sln merge=binary 26 | #*.csproj merge=binary 27 | #*.vbproj merge=binary 28 | #*.vcxproj merge=binary 29 | #*.vcproj merge=binary 30 | #*.dbproj merge=binary 31 | #*.fsproj merge=binary 32 | #*.lsproj merge=binary 33 | #*.wixproj merge=binary 34 | #*.modelproj merge=binary 35 | #*.sqlproj merge=binary 36 | #*.wwaproj merge=binary 37 | 38 | ############################################################################### 39 | # behavior for image files 40 | # 41 | # image files are treated as binary by default. 42 | ############################################################################### 43 | #*.jpg binary 44 | #*.png binary 45 | #*.gif binary 46 | 47 | ############################################################################### 48 | # diff behavior for common document formats 49 | # 50 | # Convert binary document formats to text before diffing them. This feature 51 | # is only available from the command line. Turn it on by uncommenting the 52 | # entries below. 53 | ############################################################################### 54 | #*.doc diff=astextplain 55 | #*.DOC diff=astextplain 56 | #*.docx diff=astextplain 57 | #*.DOCX diff=astextplain 58 | #*.dot diff=astextplain 59 | #*.DOT diff=astextplain 60 | #*.pdf diff=astextplain 61 | #*.PDF diff=astextplain 62 | #*.rtf diff=astextplain 63 | #*.RTF diff=astextplain 64 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | ## Ignore Visual Studio temporary files, build results, and 2 | ## files generated by popular Visual Studio add-ons. 3 | ## 4 | ## Get latest from https://github.com/github/gitignore/blob/master/VisualStudio.gitignore 5 | 6 | # User-specific files 7 | *.rsuser 8 | *.suo 9 | *.user 10 | *.userosscache 11 | *.sln.docstates 12 | 13 | # User-specific files (MonoDevelop/Xamarin Studio) 14 | *.userprefs 15 | 16 | # Mono auto generated files 17 | mono_crash.* 18 | 19 | # Build results 20 | [Dd]ebug/ 21 | [Dd]ebugPublic/ 22 | [Rr]elease/ 23 | [Rr]eleases/ 24 | x64/ 25 | x86/ 26 | [Ww][Ii][Nn]32/ 27 | [Aa][Rr][Mm]/ 28 | [Aa][Rr][Mm]64/ 29 | bld/ 30 | [Bb]in/ 31 | [Oo]bj/ 32 | [Oo]ut/ 33 | [Ll]og/ 34 | [Ll]ogs/ 35 | 36 | # Visual Studio 2015/2017 cache/options directory 37 | .vs/ 38 | # Uncomment if you have tasks that create the project's static files in wwwroot 39 | #wwwroot/ 40 | 41 | # Visual Studio 2017 auto generated files 42 | Generated\ Files/ 43 | 44 | # MSTest test Results 45 | [Tt]est[Rr]esult*/ 46 | [Bb]uild[Ll]og.* 47 | 48 | # NUnit 49 | *.VisualState.xml 50 | TestResult.xml 51 | nunit-*.xml 52 | 53 | # Build Results of an ATL Project 54 | [Dd]ebugPS/ 55 | [Rr]eleasePS/ 56 | dlldata.c 57 | 58 | # Benchmark Results 59 | BenchmarkDotNet.Artifacts/ 60 | 61 | # .NET Core 62 | project.lock.json 63 | project.fragment.lock.json 64 | artifacts/ 65 | 66 | # ASP.NET Scaffolding 67 | ScaffoldingReadMe.txt 68 | 69 | # StyleCop 70 | StyleCopReport.xml 71 | 72 | # Files built by Visual Studio 73 | *_i.c 74 | *_p.c 75 | *_h.h 76 | *.ilk 77 | *.meta 78 | *.obj 79 | *.iobj 80 | *.pch 81 | *.pdb 82 | *.ipdb 83 | *.pgc 84 | *.pgd 85 | *.rsp 86 | *.sbr 87 | *.tlb 88 | *.tli 89 | *.tlh 90 | *.tmp 91 | *.tmp_proj 92 | *_wpftmp.csproj 93 | *.log 94 | *.vspscc 95 | *.vssscc 96 | .builds 97 | *.pidb 98 | *.svclog 99 | *.scc 100 | 101 | # Chutzpah Test files 102 | _Chutzpah* 103 | 104 | # Visual C++ cache files 105 | ipch/ 106 | *.aps 107 | *.ncb 108 | *.opendb 109 | *.opensdf 110 | *.sdf 111 | *.cachefile 112 | *.VC.db 113 | *.VC.VC.opendb 114 | 115 | # Visual Studio profiler 116 | *.psess 117 | *.vsp 118 | *.vspx 119 | *.sap 120 | 121 | # Visual Studio Trace Files 122 | *.e2e 123 | 124 | # TFS 2012 Local Workspace 125 | $tf/ 126 | 127 | # Guidance Automation Toolkit 128 | *.gpState 129 | 130 | # ReSharper is a .NET coding add-in 131 | _ReSharper*/ 132 | *.[Rr]e[Ss]harper 133 | *.DotSettings.user 134 | 135 | # TeamCity is a build add-in 136 | _TeamCity* 137 | 138 | # DotCover is a Code Coverage Tool 139 | *.dotCover 140 | 141 | # AxoCover is a Code Coverage Tool 142 | .axoCover/* 143 | !.axoCover/settings.json 144 | 145 | # Coverlet is a free, cross platform Code Coverage Tool 146 | coverage*.json 147 | coverage*.xml 148 | coverage*.info 149 | 150 | # Visual Studio code coverage results 151 | *.coverage 152 | *.coveragexml 153 | 154 | # NCrunch 155 | _NCrunch_* 156 | .*crunch*.local.xml 157 | nCrunchTemp_* 158 | 159 | # MightyMoose 160 | *.mm.* 161 | AutoTest.Net/ 162 | 163 | # Web workbench (sass) 164 | .sass-cache/ 165 | 166 | # Installshield output folder 167 | [Ee]xpress/ 168 | 169 | # DocProject is a documentation generator add-in 170 | DocProject/buildhelp/ 171 | DocProject/Help/*.HxT 172 | DocProject/Help/*.HxC 173 | DocProject/Help/*.hhc 174 | DocProject/Help/*.hhk 175 | DocProject/Help/*.hhp 176 | DocProject/Help/Html2 177 | DocProject/Help/html 178 | 179 | # Click-Once directory 180 | publish/ 181 | 182 | # Publish Web Output 183 | *.[Pp]ublish.xml 184 | *.azurePubxml 185 | # Note: Comment the next line if you want to checkin your web deploy settings, 186 | # but database connection strings (with potential passwords) will be unencrypted 187 | *.pubxml 188 | *.publishproj 189 | 190 | # Microsoft Azure Web App publish settings. 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Backup files are not needed, 256 | # because we have git ;-) 257 | _UpgradeReport_Files/ 258 | Backup*/ 259 | UpgradeLog*.XML 260 | UpgradeLog*.htm 261 | ServiceFabricBackup/ 262 | *.rptproj.bak 263 | 264 | # SQL Server files 265 | *.mdf 266 | *.ldf 267 | *.ndf 268 | 269 | # Business Intelligence projects 270 | *.rdl.data 271 | *.bim.layout 272 | *.bim_*.settings 273 | *.rptproj.rsuser 274 | *- [Bb]ackup.rdl 275 | *- [Bb]ackup ([0-9]).rdl 276 | *- [Bb]ackup ([0-9][0-9]).rdl 277 | 278 | # Microsoft Fakes 279 | FakesAssemblies/ 280 | 281 | # GhostDoc plugin setting file 282 | *.GhostDoc.xml 283 | 284 | # Node.js Tools for Visual Studio 285 | .ntvs_analysis.dat 286 | node_modules/ 287 | 288 | # Visual Studio 6 build log 289 | *.plg 290 | 291 | # Visual Studio 6 workspace options file 292 | *.opt 293 | 294 | # Visual Studio 6 auto-generated workspace file (contains which files were open etc.) 295 | *.vbw 296 | 297 | # Visual Studio LightSwitch build output 298 | **/*.HTMLClient/GeneratedArtifacts 299 | **/*.DesktopClient/GeneratedArtifacts 300 | **/*.DesktopClient/ModelManifest.xml 301 | **/*.Server/GeneratedArtifacts 302 | **/*.Server/ModelManifest.xml 303 | _Pvt_Extensions 304 | 305 | # Paket dependency manager 306 | .paket/paket.exe 307 | paket-files/ 308 | 309 | # FAKE - F# Make 310 | .fake/ 311 | 312 | # CodeRush personal settings 313 | .cr/personal 314 | 315 | # Python Tools for Visual Studio (PTVS) 316 | __pycache__/ 317 | *.pyc 318 | 319 | # Cake - Uncomment if you are using it 320 | # tools/** 321 | # !tools/packages.config 322 | 323 | # Tabs Studio 324 | *.tss 325 | 326 | # Telerik's JustMock configuration file 327 | *.jmconfig 328 | 329 | # BizTalk build output 330 | *.btp.cs 331 | *.btm.cs 332 | *.odx.cs 333 | *.xsd.cs 334 | 335 | # OpenCover UI analysis results 336 | OpenCover/ 337 | 338 | # Azure Stream Analytics local run output 339 | ASALocalRun/ 340 | 341 | # MSBuild Binary and Structured Log 342 | *.binlog 343 | 344 | # NVidia Nsight GPU debugger configuration file 345 | *.nvuser 346 | 347 | # MFractors (Xamarin productivity tool) working folder 348 | .mfractor/ 349 | 350 | # Local History for Visual Studio 351 | .localhistory/ 352 | 353 | # BeatPulse healthcheck temp database 354 | healthchecksdb 355 | 356 | # Backup folder for Package Reference Convert tool in Visual Studio 2017 357 | MigrationBackup/ 358 | 359 | # Ionide (cross platform F# VS Code tools) working folder 360 | .ionide/ 361 | 362 | # Fody - auto-generated XML schema 363 | FodyWeavers.xsd -------------------------------------------------------------------------------- /Homework.sln: -------------------------------------------------------------------------------- 1 |  2 | Microsoft Visual Studio Solution File, Format Version 12.00 3 | # Visual Studio Version 16 4 | VisualStudioVersion = 16.0.31321.278 5 | MinimumVisualStudioVersion = 10.0.40219.1 6 | Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "PagesOfLargeArray", "PagesOfLargeArray\PagesOfLargeArray.csproj", "{C4E4F3CB-C2D4-4B7D-AC36-83C20AF9C46A}" 7 | EndProject 8 | Global 9 | GlobalSection(SolutionConfigurationPlatforms) = preSolution 10 | Debug|Any CPU = Debug|Any CPU 11 | Debug|x64 = Debug|x64 12 | Release|Any CPU = Release|Any CPU 13 | Release|x64 = Release|x64 14 | EndGlobalSection 15 | GlobalSection(ProjectConfigurationPlatforms) = postSolution 16 | {C4E4F3CB-C2D4-4B7D-AC36-83C20AF9C46A}.Debug|Any CPU.ActiveCfg = Debug|Any CPU 17 | {C4E4F3CB-C2D4-4B7D-AC36-83C20AF9C46A}.Debug|Any CPU.Build.0 = Debug|Any CPU 18 | {C4E4F3CB-C2D4-4B7D-AC36-83C20AF9C46A}.Debug|x64.ActiveCfg = Debug|x64 19 | {C4E4F3CB-C2D4-4B7D-AC36-83C20AF9C46A}.Debug|x64.Build.0 = Debug|x64 20 | {C4E4F3CB-C2D4-4B7D-AC36-83C20AF9C46A}.Release|Any CPU.ActiveCfg = Release|Any CPU 21 | {C4E4F3CB-C2D4-4B7D-AC36-83C20AF9C46A}.Release|Any CPU.Build.0 = Release|Any CPU 22 | {C4E4F3CB-C2D4-4B7D-AC36-83C20AF9C46A}.Release|x64.ActiveCfg = Release|x64 23 | {C4E4F3CB-C2D4-4B7D-AC36-83C20AF9C46A}.Release|x64.Build.0 = Release|x64 24 | EndGlobalSection 25 | GlobalSection(SolutionProperties) = preSolution 26 | HideSolutionNode = FALSE 27 | EndGlobalSection 28 | GlobalSection(ExtensibilityGlobals) = postSolution 29 | SolutionGuid = {7171C78B-F974-4A16-9EE4-F1E8E6988AC8} 30 | EndGlobalSection 31 | EndGlobal 32 | -------------------------------------------------------------------------------- /MemoryExpert-Slides-M08L04-Homework.pdf: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/nirzaf/PagesOfLargeArray/5aedfb03b9ed0f6c89b668a1e0994bc7346fa0a2/MemoryExpert-Slides-M08L04-Homework.pdf -------------------------------------------------------------------------------- /PagesOfLargeArray/App.config: -------------------------------------------------------------------------------- 1 |  2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | -------------------------------------------------------------------------------- /PagesOfLargeArray/PagesOfLargeArray.csproj: -------------------------------------------------------------------------------- 1 |  2 | 3 | 4 | 5 | Debug 6 | AnyCPU 7 | {C4E4F3CB-C2D4-4B7D-AC36-83C20AF9C46A} 8 | Exe 9 | PagesOfLargeArray 10 | PagesOfLargeArray 11 | v4.8 12 | 512 13 | true 14 | true 15 | 16 | 17 | AnyCPU 18 | true 19 | full 20 | false 21 | bin\Debug\ 22 | DEBUG;TRACE 23 | prompt 24 | 4 25 | 26 | 27 | AnyCPU 28 | pdbonly 29 | true 30 | bin\Release\ 31 | TRACE 32 | prompt 33 | 4 34 | 35 | 36 | true 37 | bin\x64\Debug\ 38 | DEBUG;TRACE 39 | full 40 | x64 41 | 7.3 42 | prompt 43 | true 44 | 45 | 46 | bin\x64\Release\ 47 | TRACE 48 | true 49 | pdbonly 50 | x64 51 | 7.3 52 | prompt 53 | true 54 | 55 | 56 | 57 | 58 | 59 | 60 | 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 | 71 | 72 | 73 | -------------------------------------------------------------------------------- /PagesOfLargeArray/Program.cs: -------------------------------------------------------------------------------- 1 | using System; 2 | using System.Runtime; 3 | 4 | namespace PagesOfLargeArray 5 | { 6 | class Program 7 | { 8 | static void Main(string[] args) 9 | { 10 | // Assume Background Workstation GC where LOH segment is 128MB 11 | Console.WriteLine($"ServerGC: {GCSettings.IsServerGC}, LatencyMode: {GCSettings.LatencyMode}"); 12 | Continue(); 13 | 14 | // Create two 32MB arrays. 15 | // With respect to what was said during lessons, they will be allocated in LOH and 16 | // **pre-zeroed**, because this is guaranteed from the runtime. It means that this memory 17 | // needs to be **committed** and **touched** (we write 0 for every array element). 18 | // Thus, we should expect private bytes AND working set to grow by those 64MB. 19 | var array0 = new byte[32 * 1024 * 1024]; 20 | var array1 = new byte[32 * 1024 * 1024]; 21 | Continue(); 22 | // Answer: as they are created in a LOH segment by commiting more memory it is zero-initialized 23 | // by operating system (Virtual Memory Manager) and this zeroing is "on the house": 24 | // - private bytes will grow by 64MB - those pages are really committed 25 | // - working set will not grow at all - we don't touch physical memory while "zeroing" because 26 | // it is "zeroing| from the OS. As Pavel Yosifovich, one of our mentors says: "it's using 27 | // the VirtualAlloc function behind the scenes, which guarantees you get zero pages when 28 | // they're accessed, because the zero-page thread in the kernel prepares zero pages upfront. 29 | // So, only when you make the access there is "demand zero" page fault handler that gives 30 | // you the zero-pages and thus increases the working set." 31 | // In other words, and it turns out to be pretty surprising, although we really allocate and zero 32 | // those 64MB, thanks to the operating system support this memory is not physically consumed 33 | // until we start to access them. 34 | 35 | // Get rid of array0 only, as array1 is rooted below 36 | GC.KeepAlive(array0); 37 | GC.Collect(); 38 | GC.WaitForPendingFinalizers(); 39 | GC.Collect(); 40 | Continue(); 41 | // Answer: This does not decommit anything because there is a gap in LOH now. So both private 42 | // bytes and working set stays the same level. 43 | 44 | // Create a new 32MB array. It should fit into the gap left by array0. What's the change in 45 | // private bytes and working set? What do you think, why?! 46 | var array = new byte[32 * 1024 * 1024]; 47 | Continue(); 48 | // Answer: now, while allocating in LOH, GC finds a gap and to prepare it, clears it after 49 | // previous object by zero-initializing it (memclr in gc.cpp). This is different than taking 50 | // some pages from the OS at the end of the segment (like previously). Now it really touches 51 | // this memory region (a gap) physically so we see immediate increase of working set by 32MB. 52 | // Committed stays the same. 53 | 54 | // Start to touch array page by page. What's memory usage change? 55 | var offset = 0; 56 | var sum = 0L; 57 | while (offset < 32 * 1024 * 1024) 58 | { 59 | sum += array[offset]; 60 | offset += 4096; 61 | Console.Write('.'); 62 | } 63 | Continue(); 64 | // Answer: This does not change both working set and committed because we already touched all 65 | // region physically while zeroing. 66 | 67 | // Start to touch array1 page by page. What's memory usage change? 68 | var offset2 = 0; 69 | var sum2 = 0L; 70 | while (offset2 < 32 * 1024 * 1024) 71 | { 72 | sum2 += array1[offset2]; 73 | offset2 += 4096; 74 | Console.Write('.'); 75 | } 76 | Continue(); 77 | // Answer: This does change working set because we touch "zero-pages". 78 | 79 | Console.WriteLine(sum + sum2); 80 | } 81 | 82 | static void Continue() 83 | { 84 | Console.WriteLine("Press any key to run..."); 85 | Console.ReadKey(); 86 | } 87 | } 88 | } 89 | -------------------------------------------------------------------------------- /PagesOfLargeArray/Properties/AssemblyInfo.cs: -------------------------------------------------------------------------------- 1 | using System.Reflection; 2 | using System.Runtime.CompilerServices; 3 | using System.Runtime.InteropServices; 4 | 5 | // General Information about an assembly is controlled through the following 6 | // set of attributes. Change these attribute values to modify the information 7 | // associated with an assembly. 8 | [assembly: AssemblyTitle("PagesOfLargeArray")] 9 | [assembly: AssemblyDescription("")] 10 | [assembly: AssemblyConfiguration("")] 11 | [assembly: AssemblyCompany("")] 12 | [assembly: AssemblyProduct("PagesOfLargeArray")] 13 | [assembly: AssemblyCopyright("Copyright © 2021")] 14 | [assembly: AssemblyTrademark("")] 15 | [assembly: AssemblyCulture("")] 16 | 17 | // Setting ComVisible to false makes the types in this assembly not visible 18 | // to COM components. If you need to access a type in this assembly from 19 | // COM, set the ComVisible attribute to true on that type. 20 | [assembly: ComVisible(false)] 21 | 22 | // The following GUID is for the ID of the typelib if this project is exposed to COM 23 | [assembly: Guid("c4e4f3cb-c2d4-4b7d-ac36-83c20af9c46a")] 24 | 25 | // Version information for an assembly consists of the following four values: 26 | // 27 | // Major Version 28 | // Minor Version 29 | // Build Number 30 | // Revision 31 | // 32 | // You can specify all the values or you can default the Build and Revision Numbers 33 | // by using the '*' as shown below: 34 | // [assembly: AssemblyVersion("1.0.*")] 35 | [assembly: AssemblyVersion("1.0.0.0")] 36 | [assembly: AssemblyFileVersion("1.0.0.0")] 37 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # Module08-The-Necessary-GC-Internals --------------------------------------------------------------------------------