From 4cbae07281b6c39c7dc10f321833418e24b1f92e Mon Sep 17 00:00:00 2001
From: Fabian Kozynski <kozynski@google.com>
Date: Tue, 2 Aug 2022 09:54:41 -0400
Subject: [PATCH] Reduce blocking calls to Settings in main thread

In most cases, mTileList contains the same information as the Settings
value, so there's no need to retrieve it before modifying it. Keep track
of that with a dirty flag.

This way, we reduce the number of blocking calls in the main thread (as
that's the thread that processes the tiles).

Test: manual, factory reset
Test: existing QSTileHostTest
Test: performance metrics are back to baseline
Fixes: 240256263
Change-Id: Idebd37d1458c80330b60802729575219b6a7b49a
---
 .../com/android/systemui/qs/QSTileHost.java    | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/packages/SystemUI/src/com/android/systemui/qs/QSTileHost.java b/packages/SystemUI/src/com/android/systemui/qs/QSTileHost.java
index 4552abd402b0e..77652c9ddf2fa 100644
--- a/packages/SystemUI/src/com/android/systemui/qs/QSTileHost.java
+++ b/packages/SystemUI/src/com/android/systemui/qs/QSTileHost.java
@@ -110,6 +110,11 @@ public class QSTileHost implements QSHost, Tunable, PluginListener<QSFactory>, D
     private Context mUserContext;
     private UserTracker mUserTracker;
     private SecureSettings mSecureSettings;
+    // Keep track of whether mTilesList contains the same information as the Settings value.
+    // This is a performance optimization to reduce the number of blocking calls to Settings from
+    // main thread.
+    // This is enforced by only cleaning the flag at the end of a successful run of #onTuningChanged
+    private boolean mTilesListDirty = true;
 
     private final TileServiceRequestController mTileServiceRequestController;
     private TileLifecycleManager.Factory mTileLifeCycleManagerFactory;
@@ -374,6 +379,7 @@ public class QSTileHost implements QSHost, Tunable, PluginListener<QSFactory>, D
                 // the ones that are in the setting, update the Setting.
                 saveTilesToSettings(mTileSpecs);
             }
+            mTilesListDirty = false;
             for (int i = 0; i < mCallbacks.size(); i++) {
                 mCallbacks.get(i).onTilesChanged();
             }
@@ -436,6 +442,7 @@ public class QSTileHost implements QSHost, Tunable, PluginListener<QSFactory>, D
         );
     }
 
+    // When calling this, you may want to modify mTilesListDirty accordingly.
     @MainThread
     private void saveTilesToSettings(List<String> tileSpecs) {
         mSecureSettings.putStringForUser(TILES_SETTING, TextUtils.join(",", tileSpecs),
@@ -445,9 +452,15 @@ public class QSTileHost implements QSHost, Tunable, PluginListener<QSFactory>, D
 
     @MainThread
     private void changeTileSpecs(Predicate<List<String>> changeFunction) {
-        final String setting = mSecureSettings.getStringForUser(TILES_SETTING, mCurrentUser);
-        final List<String> tileSpecs = loadTileSpecs(mContext, setting);
+        final List<String> tileSpecs;
+        if (!mTilesListDirty) {
+            tileSpecs = new ArrayList<>(mTileSpecs);
+        } else {
+            tileSpecs = loadTileSpecs(mContext,
+                    mSecureSettings.getStringForUser(TILES_SETTING, mCurrentUser));
+        }
         if (changeFunction.test(tileSpecs)) {
+            mTilesListDirty = true;
             saveTilesToSettings(tileSpecs);
         }
     }
@@ -507,6 +520,7 @@ public class QSTileHost implements QSHost, Tunable, PluginListener<QSFactory>, D
             }
         }
         if (DEBUG) Log.d(TAG, "saveCurrentTiles " + newTiles);
+        mTilesListDirty = true;
         saveTilesToSettings(newTiles);
     }