From d9b0cfd78efd2130fa24860fcb3e3f7a2170dbf4 Mon Sep 17 00:00:00 2001
From: Googler <twerth@google.com>
Date: Wed, 21 Feb 2024 06:08:57 -0800
Subject: [PATCH] Create less garbage for starlark profiles.

PiperOrigin-RevId: 608967932
Change-Id: Ieddf6a986ca068dfa3b685986a2f7e6629df1889
---
 .../build/lib/packages/PackageFactory.java      | 17 +++++++++--------
 .../devtools/build/lib/profiler/Profiler.java   |  8 ++++++--
 .../net/starlark/java/eval/StarlarkThread.java  | 13 +++++++------
 3 files changed, 22 insertions(+), 16 deletions(-)

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 31f0cbcd935943..37398aadd16679 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
@@ -563,19 +563,20 @@ public void end(Object span) {
     StarlarkThread.setCallProfiler(
         new StarlarkThread.CallProfiler() {
           @Override
-          public Object start(StarlarkCallable fn) {
-            return Profiler.instance()
-                .profile(
+          public long start() {
+            return Profiler.nanoTimeMaybe();
+          }
+
+          @Override
+          public void end(long startTimeNanos, StarlarkCallable fn) {
+            Profiler.instance()
+                .completeTask(
+                    startTimeNanos,
                     fn instanceof StarlarkFunction
                         ? ProfilerTask.STARLARK_USER_FN
                         : ProfilerTask.STARLARK_BUILTIN_FN,
                     fn.getName());
           }
-
-          @Override
-          public void end(Object span) {
-            ((SilentCloseable) span).close();
-          }
         });
   }
 }
diff --git a/src/main/java/com/google/devtools/build/lib/profiler/Profiler.java b/src/main/java/com/google/devtools/build/lib/profiler/Profiler.java
index e790782f73ea8d..845bb3750f3865 100644
--- a/src/main/java/com/google/devtools/build/lib/profiler/Profiler.java
+++ b/src/main/java/com/google/devtools/build/lib/profiler/Profiler.java
@@ -74,6 +74,7 @@
  * @see ProfilerTask enum for recognized task types.
  */
 @ThreadSafe
+@SuppressWarnings("GoodTime") // This code is very performance sensitive.
 public final class Profiler {
   /** The profiler (a static singleton instance). Inactive by default. */
   private static final Profiler instance = new Profiler();
@@ -802,14 +803,17 @@ private boolean countAction(ProfilerTask type, TaskData taskData) {
         || (type == ProfilerTask.INFO && "discoverInputs".equals(taskData.description));
   }
 
+  public void completeTask(long startTimeNanos, ProfilerTask type, String description) {
+    completeTask(Thread.currentThread().getId(), startTimeNanos, type, description);
+  }
+
   /** Records the end of the task. */
   private void completeTask(
       long laneId, long startTimeNanos, ProfilerTask type, String description) {
     if (isActive()) {
       long endTimeNanos = clock.nanoTime();
       long duration = endTimeNanos - startTimeNanos;
-      boolean shouldRecordTask = wasTaskSlowEnoughToRecord(type, duration);
-      if (shouldRecordTask) {
+      if (wasTaskSlowEnoughToRecord(type, duration)) {
         recordTask(new TaskData(laneId, startTimeNanos, duration, type, description));
       }
     }
diff --git a/src/main/java/net/starlark/java/eval/StarlarkThread.java b/src/main/java/net/starlark/java/eval/StarlarkThread.java
index fd9774933605ec..f4c202a2429d48 100644
--- a/src/main/java/net/starlark/java/eval/StarlarkThread.java
+++ b/src/main/java/net/starlark/java/eval/StarlarkThread.java
@@ -142,7 +142,7 @@ static final class Frame implements Debug.Frame {
     // values, or wrapped in StarlarkFunction.Cells if shared with a nested function.
     @Nullable Object[] locals;
 
-    @Nullable private Object profileSpan; // current span of walltime call profiler
+    private long profileStartTimeNanos; // start time nanos of walltime call profiler
 
     private Frame(StarlarkThread thread, StarlarkCallable fn) {
       this.thread = thread;
@@ -237,7 +237,7 @@ void push(StarlarkCallable fn) {
     // Start wall-time call profile span.
     CallProfiler callProfiler = StarlarkThread.callProfiler;
     if (callProfiler != null) {
-      fr.profileSpan = callProfiler.start(fn);
+      fr.profileStartTimeNanos = callProfiler.start();
     }
 
     // Poll for newly installed CPU profiler.
@@ -277,8 +277,8 @@ void pop() {
 
     // End wall-time profile span.
     CallProfiler callProfiler = StarlarkThread.callProfiler;
-    if (callProfiler != null && fr.profileSpan != null) {
-      callProfiler.end(fr.profileSpan);
+    if (callProfiler != null && fr.profileStartTimeNanos >= 0) {
+      callProfiler.end(fr.profileStartTimeNanos, fr.fn);
     }
 
     // Notify debug tools of the thread's last pop.
@@ -570,9 +570,10 @@ public String toString() {
 
   /** CallProfiler records the start and end wall times of function calls. */
   public interface CallProfiler {
-    Object start(StarlarkCallable fn);
+    long start();
 
-    void end(Object span);
+    @SuppressWarnings("GoodTime") // This code is very performance sensitive.
+    void end(long startTimeNanos, StarlarkCallable fn);
   }
 
   /** Installs a global hook that will be notified of function calls. */