Properly rebuild optimization data when it changes (#56397)

The timestamp of the merged .mibc file was set to when the tool was
invoked, while the inputs have a timestamp from when they were created
in the training scenarios. That means the target to create the merged
.mibc file would not run incrementally until many weeks later.

To fix add an --inherit-timestamp flag to dotnet-pgo that makes the
merged output inherit the max timestamp from the inputs. This is not
ideal as it means incrementally going backwards does not work, but it's
better than the previous behavior.

Fix #53637

diff --git a/src/coreclr/crossgen-corelib.proj b/src/coreclr/crossgen-corelib.proj
index 6d675a2a59e247aeed7252b300add935e9ada923..655fc3281eb2efe1328ad0e8f1e2dd79df287ae9 100644 (file)
--- a/src/coreclr/crossgen-corelib.proj
+++ b/src/coreclr/crossgen-corelib.proj
@@ -66,6 +66,7 @@
       <DotNetPgoCmd>$(DotNetCli) $([MSBuild]::NormalizePath('$(BinDir)', 'dotnet-pgo', 'dotnet-pgo.dll')) merge</DotNetPgoCmd>
       <DotNetPgoCmd>$(DotNetPgoCmd) -o:$(MergedMibcPath)</DotNetPgoCmd>
       <DotNetPgoCmd>$(DotNetPgoCmd) @(OptimizationMibcFiles->'-i:%(Identity)', ' ')</DotNetPgoCmd>
+      <DotNetPgoCmd>$(DotNetPgoCmd) --inherit-timestamp</DotNetPgoCmd> <!-- For incremental builds, otherwise timestamp is too far in the future -->
     </PropertyGroup>
 
     <Message Condition="'$(DotNetBuildFromSource)' != 'true'" Importance="High" Text="$(DotNetPgoCmd)"/>

diff --git a/src/coreclr/tools/dotnet-pgo/CommandLineOptions.cs b/src/coreclr/tools/dotnet-pgo/CommandLineOptions.cs
index 3da9ded70632f77d04709f251528e3aadb41ef35..a2e3a82f37fdb66928eaadcf27b2a1f2a165038f 100644 (file)
--- a/src/coreclr/tools/dotnet-pgo/CommandLineOptions.cs
+++ b/src/coreclr/tools/dotnet-pgo/CommandLineOptions.cs
@@ -45,6 +45,7 @@ namespace Microsoft.Diagnostics.Tools.Pgo
         public bool DumpMibc = false;
         public FileInfo InputFileToDump;
         public List<FileInfo> CompareMibc;
+        public bool InheritTimestamp;
 
         public string[] HelpArgs = Array.Empty<string>();
 
@@ -265,6 +266,8 @@ namespace Microsoft.Diagnostics.Tools.Pgo
                     }
                 }
 
+                syntax.DefineOption(name: "inherit-timestamp", value: ref InheritTimestamp, help: "If specified, set the output's timestamp to the max timestamp of the input files");
+
                 VerbosityOption();
                 CompressedOption();
                 HelpOption();

diff --git a/src/coreclr/tools/dotnet-pgo/Program.cs b/src/coreclr/tools/dotnet-pgo/Program.cs
index f129fdfee59bf475bde7ac83110cac9d00d105bc..77113377c478ddd80af81cd74d7737d595d7da33 100644 (file)
--- a/src/coreclr/tools/dotnet-pgo/Program.cs
+++ b/src/coreclr/tools/dotnet-pgo/Program.cs
@@ -378,7 +378,14 @@ namespace Microsoft.Diagnostics.Tools.Pgo
                     ProfileData.MergeProfileData(ref partialNgen, mergedProfileData, MIbcProfileParser.ParseMIbcFile(tsc, peReader, assemblyNamesInBubble, onlyDefinedInAssembly: null));
                 }
 
-                return MibcEmitter.GenerateMibcFile(tsc, commandLineOptions.OutputFileName, mergedProfileData.Values, commandLineOptions.ValidateOutputFile, commandLineOptions.Uncompressed);
+                int result = MibcEmitter.GenerateMibcFile(tsc, commandLineOptions.OutputFileName, mergedProfileData.Values, commandLineOptions.ValidateOutputFile, commandLineOptions.Uncompressed);
+                if (result == 0 && commandLineOptions.InheritTimestamp)
+                {
+                    commandLineOptions.OutputFileName.CreationTimeUtc = commandLineOptions.InputFilesToMerge.Max(fi => fi.CreationTimeUtc);
+                    commandLineOptions.OutputFileName.LastWriteTimeUtc = commandLineOptions.InputFilesToMerge.Max(fi => fi.LastWriteTimeUtc);
+                }
+
+                return result;
             }
             finally
             {