commit e6e3c0d6aed6c46ad3ca83547114e1211c6ece8b
author Marissa Wall <marissaw@google.com> Fri Mar 29 10:28:30 2019 -0700
committer Marissa Wall <marissaw@google.com> Sun Mar 31 12:44:30 2019 -0700
tree c3a28b5e22c8057dd69338d050e5bd459ae1d71b
parent eccfc576b3f90c2ee818de7c10eea6fdbbe2d166

blast: flush transaction wake ups

When SurfaceFlinger's main thread wakes up just to flush
transactions and no transactions are ready to be flushed, go back
to sleep.

Bug: 128520233
Test: Play a 30hz video that has desiredPresentTimes. Check that
    SurfaceFlinger is only doing a full present cycle 30 times
    a second.

Change-Id: Iae11f9a604a3ea5b0d553947f47133871e608fca

services/surfaceflinger/SurfaceFlinger.cpp

diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index fae4b81..7061ad6 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -1709,22 +1709,22 @@
     ATRACE_CALL();
     uint32_t transactionFlags = peekTransactionFlags();
 
-    // Apply any ready transactions in the queues if there are still transactions that have not been
-    // applied, wake up during the next vsync period and check again
-    bool transactionNeeded = false;
-    if (!flushTransactionQueues()) {
-        transactionNeeded = true;
+    bool flushedATransaction = flushTransactionQueues();
+
+    bool runHandleTransaction = transactionFlags &&
+            ((transactionFlags != eTransactionFlushNeeded) || flushedATransaction);
+
+    if (runHandleTransaction) {
+        handleTransaction(eTransactionMask);
+    } else {
+        getTransactionFlags(eTransactionFlushNeeded);
     }
 
-    if (transactionFlags) {
-        handleTransaction(transactionFlags);
+    if (transactionFlushNeeded()) {
+        setTransactionFlags(eTransactionFlushNeeded);
     }
 
-    if (transactionNeeded) {
-        setTransactionFlags(eTransactionNeeded);
-    }
-
-    return transactionFlags;
+    return runHandleTransaction;
 }
 
 void SurfaceFlinger::handleMessageRefresh() {
@@ -3522,6 +3522,8 @@
 
 bool SurfaceFlinger::flushTransactionQueues() {
     Mutex::Autolock _l(mStateLock);
+    bool flushedATransaction = false;
+
     auto it = mTransactionQueues.begin();
     while (it != mTransactionQueues.end()) {
         auto& [applyToken, transactionQueue] = *it;
@@ -3531,17 +3533,23 @@
                     [states, displays, flags, desiredPresentTime, uncacheBuffer, listenerCallbacks,
                      postTime, privileged] = transactionQueue.front();
             if (!transactionIsReadyToBeApplied(desiredPresentTime, states)) {
+                setTransactionFlags(eTransactionFlushNeeded);
                 break;
             }
             applyTransactionState(states, displays, flags, mPendingInputWindowCommands,
                                   desiredPresentTime, uncacheBuffer, listenerCallbacks, postTime,
                                   privileged, /*isMainThread*/ true);
             transactionQueue.pop();
+            flushedATransaction = true;
         }
 
         it = (transactionQueue.empty()) ? mTransactionQueues.erase(it) : std::next(it, 1);
     }
-    return mTransactionQueues.empty();
+    return flushedATransaction;
+}
+
+bool SurfaceFlinger::transactionFlushNeeded() {
+    return !mTransactionQueues.empty();
 }
 
 bool SurfaceFlinger::containsAnyInvalidClientState(const Vector<ComposerState>& states) {
@@ -3613,7 +3621,7 @@
         mTransactionQueues[applyToken].emplace(states, displays, flags, desiredPresentTime,
                                                uncacheBuffer, listenerCallbacks, postTime,
                                                privileged);
-        setTransactionFlags(eTransactionNeeded);
+        setTransactionFlags(eTransactionFlushNeeded);
         return;
     }
 

services/surfaceflinger/SurfaceFlinger.h

diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 3d8b6b7..f176e06 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -135,11 +135,12 @@
 // ---------------------------------------------------------------------------
 
 enum {
-    eTransactionNeeded        = 0x01,
-    eTraversalNeeded          = 0x02,
+    eTransactionNeeded = 0x01,
+    eTraversalNeeded = 0x02,
     eDisplayTransactionNeeded = 0x04,
     eDisplayLayerStackChanged = 0x08,
-    eTransactionMask          = 0x0f,
+    eTransactionFlushNeeded = 0x10,
+    eTransactionMask = 0x1f,
 };
 
 enum class DisplayColorSetting : int32_t {
@@ -606,7 +607,10 @@
                                const std::vector<ListenerCallbacks>& listenerCallbacks,
                                const int64_t postTime, bool privileged, bool isMainThread = false)
             REQUIRES(mStateLock);
+    // Returns true if at least one transaction was flushed
     bool flushTransactionQueues();
+    // Returns true if there is at least one transaction that needs to be flushed
+    bool transactionFlushNeeded();
     uint32_t getTransactionFlags(uint32_t flags);
     uint32_t peekTransactionFlags();
     // Can only be called from the main thread or with mStateLock held