Pre-allocate memory at a few (non-exhaustive) sites that are on the exit path after we OOM, in an attempt to make that path complete more quickly and successfully.

--
MOS_MIGRATED_REVID=123040502

2 files changed, 16 insertions, 5 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/runtime/BlazeRuntime.java b/src/main/java/com/google/devtools/build/lib/runtime/BlazeRuntime.java
index e9a91dcee4..8c9af364ce 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/BlazeRuntime.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/BlazeRuntime.java
@@ -141,6 +141,10 @@ public final class BlazeRuntime {
 
   private static final Logger LOG = Logger.getLogger(BlazeRuntime.class.getName());
 
+  // Pre-allocate memory for this object in case of an OOM.
+  private static final CommandCompleteEvent OOM_COMMAND_COMPLETE_EVENT =
+      new CommandCompleteEvent(ExitCode.OOM_ERROR.getNumericExitCode());
+
   private final Iterable<BlazeModule> blazeModules;
   private final Map<String, BlazeCommand> commandMap = new LinkedHashMap<>();
   private final Clock clock;
@@ -505,14 +509,18 @@ public final class BlazeRuntime {
    * Posts the {@link CommandCompleteEvent}, so that listeners can tidy up. Called by {@link
    * #afterCommand}, and by BugReport when crashing from an exception in an async thread.
    */
-  public void notifyCommandComplete(int exitCode) {
+  void notifyCommandComplete(int exitCode) {
     if (!storedExitCode.compareAndSet(ExitCode.RESERVED.getNumericExitCode(), exitCode)) {
       // This command has already been called, presumably because there is a race between the main
       // thread and a worker thread that crashed. Don't try to arbitrate the dispute. If the main
       // thread won the race (unlikely, but possible), this may be incorrectly logged as a success.
       return;
     }
-    workspace.getSkyframeExecutor().getEventBus().post(new CommandCompleteEvent(exitCode));
+    CommandCompleteEvent commandCompleteEvent =
+        exitCode == ExitCode.OOM_ERROR.getNumericExitCode()
+            ? OOM_COMMAND_COMPLETE_EVENT
+            : new CommandCompleteEvent(exitCode);
+    workspace.getSkyframeExecutor().getEventBus().post(commandCompleteEvent);
   }
 
   /**
diff --git a/src/main/java/com/google/devtools/build/lib/runtime/OomSignalHandler.java b/src/main/java/com/google/devtools/build/lib/runtime/OomSignalHandler.java
index 39c2c8902c..3aea75e6d9 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/OomSignalHandler.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/OomSignalHandler.java
@@ -30,6 +30,10 @@ import java.util.logging.Logger;
 class OomSignalHandler extends AbstractSignalHandler {
   private static final Logger LOG = Logger.getLogger(OomSignalHandler.class.getName());
   private static final Signal SIGUSR2 = new Signal("USR2");
+  private static final String MESSAGE = "SIGUSR2 received, presumably from JVM due to OOM";
+  // Pre-allocate memory for object that will be used during an OOM, because there may not be spare
+  // memory when we're OOMing. That's kind of the point of an OOM.
+  private static final OutOfMemoryError OUT_OF_MEMORY_ERROR = new OutOfMemoryError(MESSAGE);
 
   OomSignalHandler() {
     super(SIGUSR2);
@@ -37,10 +41,9 @@ class OomSignalHandler extends AbstractSignalHandler {
 
   @Override
   protected void onSignal() {
-    String message = "SIGUSR2 received, presumably from JVM due to OOM";
-    LOG.info(message);
+    LOG.info(MESSAGE);
     OutErr.SYSTEM_OUT_ERR.printErrLn(
         "Exiting as if we OOM'd because SIGUSR2 received, presumably from JVM");
-    BugReport.handleCrash(new OutOfMemoryError(message));
+    BugReport.handleCrash(OUT_OF_MEMORY_ERROR);
   }
 }