When we don't have an OutputService, precompute and cache the assumed-to-be-immutable filesystem type of output_base.

When we do have an OutputService, defer computation of the OutputService's dynamic filesystem type until we actually need it at the start of a "build" or "test" command.

This saves ~450us on each invocation, according to my benchmarks.

--
MOS_MIGRATED_REVID=121156323

3 files changed, 24 insertions, 17 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/buildtool/BuildTool.java b/src/main/java/com/google/devtools/build/lib/buildtool/BuildTool.java
index f04eab4f96..182b74cd14 100644
--- a/src/main/java/com/google/devtools/build/lib/buildtool/BuildTool.java
+++ b/src/main/java/com/google/devtools/build/lib/buildtool/BuildTool.java
@@ -152,7 +152,7 @@ public final class BuildTool {
     BuildConfigurationCollection configurations = null;
     boolean catastrophe = false;
     try {
-      env.getEventBus().post(new BuildStartingEvent(env.getOutputFileSystem(), request));
+      env.getEventBus().post(new BuildStartingEvent(env.determineOutputFileSystem(), request));
       LOG.info("Build identifier: " + request.getId());
       executionTool = new ExecutionTool(env, request);
       if (needsExecutionPhase(request.getBuildOptions())) {
diff --git a/src/main/java/com/google/devtools/build/lib/runtime/BlazeWorkspace.java b/src/main/java/com/google/devtools/build/lib/runtime/BlazeWorkspace.java
index aa98d3b98a..6652bd74ab 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/BlazeWorkspace.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/BlazeWorkspace.java
@@ -69,6 +69,8 @@ public final class BlazeWorkspace {
   @Nullable
   private Range<Long> lastExecutionRange = null;
 
+  private final String outputBaseFilesystemTypeName;
+
   public BlazeWorkspace(BlazeRuntime runtime, BlazeDirectories directories,
       SkyframeExecutor skyframeExecutor, SubscriberExceptionHandler eventBusExceptionHandler,
       WorkspaceStatusAction.Factory workspaceStatusActionFactory, BinTools binTools) {
@@ -85,6 +87,9 @@ public final class BlazeWorkspace {
       writeDoNotBuildHereFile(runtime.getStartupOptionsProvider());
     }
     setupExecRoot();
+    // Here we use outputBase instead of outputPath because we need a file system to create the
+    // latter.
+    this.outputBaseFilesystemTypeName = FileSystemUtils.getFileSystem(getOutputBase());
   }
 
   /**
@@ -126,6 +131,15 @@ public final class BlazeWorkspace {
   }
 
   /**
+   * Returns the cached value of
+   * {@code getOutputBase().getFilesystem().getFileSystemType(getOutputBase())}, which is assumed
+   * to be constant for a fixed workspace for the life of the Blaze server.
+   */
+  public String getOutputBaseFilesystemTypeName() {
+    return outputBaseFilesystemTypeName;
+  }
+
+  /**
    * Returns the output path associated with this Blaze server process..
    */
   public Path getOutputPath() {
diff --git a/src/main/java/com/google/devtools/build/lib/runtime/CommandEnvironment.java b/src/main/java/com/google/devtools/build/lib/runtime/CommandEnvironment.java
index 0900086aca..38eac7f230 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/CommandEnvironment.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/CommandEnvironment.java
@@ -87,7 +87,6 @@ public final class CommandEnvironment {
   private PathFragment relativeWorkingDirectory = PathFragment.EMPTY_FRAGMENT;
   private long commandStartTime;
   private OutputService outputService;
-  private String outputFileSystem;
   private Path workingDirectory;
 
   private AtomicReference<AbruptExitException> pendingException = new AtomicReference<>();
@@ -413,10 +412,6 @@ public final class CommandEnvironment {
     this.workingDirectory = workingDirectory;
   }
 
-  public String getOutputFileSystem() {
-    return outputFileSystem;
-  }
-
   /**
    * Hook method called by the BlazeCommandDispatcher prior to the dispatch of
    * each command.
@@ -450,8 +445,6 @@ public final class CommandEnvironment {
     SkyframeExecutor skyframeExecutor = getSkyframeExecutor();
     skyframeExecutor.setOutputService(outputService);
 
-    this.outputFileSystem = determineOutputFileSystem();
-
     // Ensure that the working directory will be under the workspace directory.
     Path workspace = getWorkspace();
     Path workingDirectory;
@@ -507,16 +500,16 @@ public final class CommandEnvironment {
         new CommandStartEvent(command.name(), commandId, getClientEnv(), workingDirectory));
   }
 
-  /**
-   * Figures out what file system we are writing output to. Here we use
-   * outputBase instead of outputPath because we need a file system to create the latter.
-   */
-  private String determineOutputFileSystem() {
+  /** Returns the name of the file system we are writing output to. */
+  public String determineOutputFileSystem() {
+    // If we have a fancy OutputService, this may be different between consecutive Blaze commands
+    // and so we need to compute it freshly. Otherwise, we can used the immutable value that's
+    // precomputed by our BlazeWorkspace.
     if (getOutputService() != null) {
-      return getOutputService().getFilesSystemName();
-    }
-    try (AutoProfiler p = profiled("Finding output file system", ProfilerTask.INFO)) {
-      return FileSystemUtils.getFileSystem(getOutputBase());
+      try (AutoProfiler p = profiled("Finding output file system", ProfilerTask.INFO)) {
+        return getOutputService().getFilesSystemName();
+      }
     }
+    return workspace.getOutputBaseFilesystemTypeName();
   }
 }