From e4d86a6e1e6b0503ffe6a3fac3bae7ab98d5ce97 Mon Sep 17 00:00:00 2001
From: Riddle Hsu <riddlehsu@google.com>
Date: Thu, 3 Nov 2022 12:35:19 +0000
Subject: [PATCH] Remove manual GC after unfreezing screen

The modern VM should be efficient enough to do GC automatically
on a dedicated thread. The removal can avoid significant random
delay by the explicitly GC on display thread.

About the legacy comment of "remote references", there is no strong
association with display change. There could have other cases to
produce many releasable remote references, but so far they are no
problem without an explicitly GC. Hence remove the manual GC to be
more general.

Bug: 255687140
Test: CtsWindowManagerDeviceTestCases
Change-Id: Ib620894b103ae33f1859a6e1d9627703eeb7b0ae
---
 .../server/wm/WindowManagerService.java       | 29 -------------------
 1 file changed, 29 deletions(-)

diff --git a/services/core/java/com/android/server/wm/WindowManagerService.java b/services/core/java/com/android/server/wm/WindowManagerService.java
index 848c231bb568e..edb80d73e95f6 100644
--- a/services/core/java/com/android/server/wm/WindowManagerService.java
+++ b/services/core/java/com/android/server/wm/WindowManagerService.java
@@ -5295,7 +5295,6 @@ public class WindowManagerService extends IWindowManager.Stub
         public static final int WINDOW_FREEZE_TIMEOUT = 11;
 
         public static final int PERSIST_ANIMATION_SCALE = 14;
-        public static final int FORCE_GC = 15;
         public static final int ENABLE_SCREEN = 16;
         public static final int APP_FREEZE_TIMEOUT = 17;
         public static final int REPORT_WINDOWS_CHANGE = 19;
@@ -5386,26 +5385,6 @@ public class WindowManagerService extends IWindowManager.Stub
                     break;
                 }
 
-                case FORCE_GC: {
-                    synchronized (mGlobalLock) {
-                        // Since we're holding both mWindowMap and mAnimator we don't need to
-                        // hold mAnimator.mLayoutToAnim.
-                        if (mAnimator.isAnimationScheduled()) {
-                            // If we are animating, don't do the gc now but
-                            // delay a bit so we don't interrupt the animation.
-                            sendEmptyMessageDelayed(H.FORCE_GC, 2000);
-                            return;
-                        }
-                        // If we are currently rotating the display, it will
-                        // schedule a new message when done.
-                        if (mDisplayFrozen) {
-                            return;
-                        }
-                    }
-                    Runtime.getRuntime().gc();
-                    break;
-                }
-
                 case ENABLE_SCREEN: {
                     performEnableScreen();
                     break;
@@ -6264,14 +6243,6 @@ public class WindowManagerService extends IWindowManager.Stub
         // now to catch that.
         configChanged = displayContent != null && displayContent.updateOrientation();
 
-        // A little kludge: a lot could have happened while the
-        // display was frozen, so now that we are coming back we
-        // do a gc so that any remote references the system
-        // processes holds on others can be released if they are
-        // no longer needed.
-        mH.removeMessages(H.FORCE_GC);
-        mH.sendEmptyMessageDelayed(H.FORCE_GC, 2000);
-
         mScreenFrozenLock.release();
 
         if (updateRotation && displayContent != null) {