Fix render thread priority for allocateBuffers

Increase the prio for the thread allocateBuffer runs on
 so we don't cause the main RT prio thread wait as long
 during frame draws.

Bug: 399701430
Test: app launch test
Flag: com.android.graphics.libgui.flags.allocate_buffer_priority

Change-Id: Ic56697866f1f58c6c5575909da9e1ecd95a3cb06

Author: “Shadman

libs/gui/BLASTBufferQueue.cpp

@@ -937,15 +937,22 @@ class BBQSurface : public Surface {
           : Surface(igbp, controlledByApp, scHandle), mBbq(bbq) {}
 
     void allocateBuffers() override {
+        ATRACE_CALL();
         uint32_t reqWidth = mReqWidth ? mReqWidth : mUserWidth;
         uint32_t reqHeight = mReqHeight ? mReqHeight : mUserHeight;
         auto gbp = getIGraphicBufferProducer();
-        std::thread ([reqWidth, reqHeight, gbp=getIGraphicBufferProducer(),
-                      reqFormat=mReqFormat, reqUsage=mReqUsage] () {
+        std::thread allocateThread([reqWidth, reqHeight, gbp = getIGraphicBufferProducer(),
+                                    reqFormat = mReqFormat, reqUsage = mReqUsage]() {
+            if (com_android_graphics_libgui_flags_allocate_buffer_priority()) {
+                androidSetThreadName("allocateBuffers");
+                pid_t tid = gettid();
+                androidSetThreadPriority(tid, ANDROID_PRIORITY_DISPLAY);
+            }
+
             gbp->allocateBuffers(reqWidth, reqHeight,
                                  reqFormat, reqUsage);
-
-        }).detach();
+        });
+        allocateThread.detach();
     }
 
     status_t setFrameRate(float frameRate, int8_t compatibility,

libs/gui/libgui_flags.aconfig

@@ -142,3 +142,14 @@ flag {
   bug: "340934031"
   is_fixed_read_only: true
 } # wb_media_migration
+
+flag {
+  name: "allocate_buffer_priority"
+  namespace: "wear_system_health"
+  description: "Boost priority for buffer allocation"
+  bug: "399701430"
+  metadata {
+    purpose: PURPOSE_BUGFIX
+  }
+  is_fixed_read_only: true
+} # allocate_buffer_priority