Add a hidden flag which allows us to set the size of the legacy globbing thread pool.

--
MOS_MIGRATED_REVID=94236393
diff --git a/src/main/java/com/google/devtools/build/lib/packages/PackageFactory.java b/src/main/java/com/google/devtools/build/lib/packages/PackageFactory.java
index 4d7b71f..02c7f03 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/PackageFactory.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/PackageFactory.java
@@ -366,7 +366,7 @@
     globalEnv = newGlobalEnvironment();
     threadPool = new ThreadPoolExecutor(100, 100, 3L, TimeUnit.SECONDS,
         new LinkedBlockingQueue<Runnable>(),
-        new ThreadFactoryBuilder().setNameFormat("PackageFactory %d").build());
+        new ThreadFactoryBuilder().setNameFormat("Legacy globber %d").build());
     // Do not consume threads when not in use.
     threadPool.allowCoreThreadTimeOut(true);
     this.environmentExtensions = ImmutableList.copyOf(environmentExtensions);
@@ -388,6 +388,15 @@
   }
 
   /**
+   * Sets the max number of threads to use for globbing.
+   */
+  public void setGlobbingThreads(int globbingThreads) {
+    threadPool.setCorePoolSize(globbingThreads);
+    threadPool.setMaximumPoolSize(globbingThreads);
+  }
+
+
+  /**
    * Returns the static environment initialized once and shared by all packages
    * created by this factory. No updates occur to this environment once created.
    */
diff --git a/src/main/java/com/google/devtools/build/lib/pkgcache/PackageCacheOptions.java b/src/main/java/com/google/devtools/build/lib/pkgcache/PackageCacheOptions.java
index 6db7cf6..e57fe0d 100644
--- a/src/main/java/com/google/devtools/build/lib/pkgcache/PackageCacheOptions.java
+++ b/src/main/java/com/google/devtools/build/lib/pkgcache/PackageCacheOptions.java
@@ -120,6 +120,12 @@
           + "'private').")
   public RuleVisibility defaultVisibility;
 
+  @Option(name = "legacy_globbing_threads",
+      defaultValue = "100",
+      category = "undocumented",
+      help = "Number of threads to use for glob evaluation.")
+  public int globbingThreads;
+
   @Option(name = "min_pkg_count_for_ct_node_eviction",
       defaultValue = "3700",
       // Why is the default value 3700? As of December 2013, a medium target loads about this many
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java b/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java
index f2ad498..ca12499 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java
@@ -735,8 +735,8 @@
    */
   @VisibleForTesting  // productionVisibility = Visibility.PRIVATE
   public void preparePackageLoading(PathPackageLocator pkgLocator, RuleVisibility defaultVisibility,
-      boolean showLoadingProgress,
-      String defaultsPackageContents, UUID commandId) {
+                                    boolean showLoadingProgress, int globbingThreads,
+                                    String defaultsPackageContents, UUID commandId) {
     Preconditions.checkNotNull(pkgLocator);
     setActive(true);
 
@@ -748,6 +748,7 @@
     setPackageLocator(pkgLocator);
 
     syscalls.set(new PerBuildSyscallCache());
+    this.pkgFactory.setGlobbingThreads(globbingThreads);
     checkPreprocessorFactory();
     emittedEventState.clear();
 
@@ -1328,7 +1329,7 @@
     preparePackageLoading(
         createPackageLocator(packageCacheOptions, directories.getWorkspace(), workingDirectory),
         packageCacheOptions.defaultVisibility, packageCacheOptions.showLoadingProgress,
-        defaultsPackageContents, commandId);
+        packageCacheOptions.globbingThreads, defaultsPackageContents, commandId);
     setDeletedPackages(ImmutableSet.copyOf(packageCacheOptions.deletedPackages));
 
     incrementalBuildMonitor = new SkyframeIncrementalBuildMonitor();