SF: change acquired buffers based on the current refresh rate

BLASTBufferQueue set the max acquired buffers based on SF
vsync configuration (sf.duration and app.duration). This is calculated
based on the max supported refresh rate on the device, and it turn
is propogated to apps via min_undequeued_buffers to the app could
allocate enough buffers for maintaining the pipeline SF expects.

This leads to a higher latency when the device is running in a lower
refresh rate as there are more buffers on the buffer queue then required.
In this change we are holding on the these "extra buffers" and not
releasing them back to the buffer queue so the app would use the number
of buffers it needs based on the current refresh rate, and to avoid having
unnecessary long latency.

Bug: 188553729
Test: Run backpressure based game on 60Hz and 120Hz and collect systraces
Change-Id: I9d4e6278f0ddd28008ac437ab0576aa79d05166a

1 files changed, 14 insertions, 7 deletions

diff --git a/services/surfaceflinger/BufferStateLayer.cpp b/services/surfaceflinger/BufferStateLayer.cpp
index d68a0e0b47..955c2f88b0 100644
--- a/services/surfaceflinger/BufferStateLayer.cpp
+++ b/services/surfaceflinger/BufferStateLayer.cpp
@@ -44,12 +44,12 @@ using PresentState = frametimeline::SurfaceFrame::PresentState;
 namespace {
 void callReleaseBufferCallback(const sp<ITransactionCompletedListener>& listener,
                                const sp<GraphicBuffer>& buffer, const sp<Fence>& releaseFence,
-                               uint32_t transformHint) {
+                               uint32_t transformHint, uint32_t currentMaxAcquiredBufferCount) {
     if (!listener) {
         return;
     }
     listener->onReleaseBuffer(buffer->getId(), releaseFence ? releaseFence : Fence::NO_FENCE,
-                              transformHint);
+                              transformHint, currentMaxAcquiredBufferCount);
 }
 } // namespace
 
@@ -75,7 +75,9 @@ BufferStateLayer::~BufferStateLayer() {
     if (mBufferInfo.mBuffer != nullptr && !isClone()) {
         callReleaseBufferCallback(mDrawingState.releaseBufferListener,
                                   mBufferInfo.mBuffer->getBuffer(), mBufferInfo.mFence,
-                                  mTransformHint);
+                                  mTransformHint,
+                                  mFlinger->getMaxAcquiredBufferCountForCurrentRefreshRate(
+                                          mOwnerUid));
     }
 }
 
@@ -199,6 +201,8 @@ void BufferStateLayer::releasePendingBuffer(nsecs_t dequeueReadyTime) {
     for (const auto& handle : mDrawingState.callbackHandles) {
         handle->transformHint = mTransformHint;
         handle->dequeueReadyTime = dequeueReadyTime;
+        handle->currentMaxAcquiredBufferCount =
+                mFlinger->getMaxAcquiredBufferCountForCurrentRefreshRate(mOwnerUid);
     }
 
     // If there are multiple transactions in this frame, set the previous id on the earliest
@@ -429,9 +433,10 @@ bool BufferStateLayer::setBuffer(const std::shared_ptr<renderengine::ExternalTex
             // dropped and we should decrement the pending buffer count and
             // call any release buffer callbacks if set.
             callReleaseBufferCallback(mCurrentState.releaseBufferListener,
-                                      mCurrentState.buffer->getBuffer(),
-                                      mCurrentState.acquireFence,
-                                      mTransformHint);
+                                      mCurrentState.buffer->getBuffer(), mCurrentState.acquireFence,
+                                      mTransformHint,
+                                      mFlinger->getMaxAcquiredBufferCountForCurrentRefreshRate(
+                                              mOwnerUid));
             decrementPendingBufferCount();
             if (mCurrentState.bufferSurfaceFrameTX != nullptr) {
                 addSurfaceFrameDroppedForBuffer(mCurrentState.bufferSurfaceFrameTX);
@@ -951,7 +956,9 @@ void BufferStateLayer::bufferMayChange(const sp<GraphicBuffer>& newBuffer) {
         // call any release buffer callbacks if set.
         callReleaseBufferCallback(mDrawingState.releaseBufferListener,
                                   mDrawingState.buffer->getBuffer(), mDrawingState.acquireFence,
-                                  mTransformHint);
+                                  mTransformHint,
+                                  mFlinger->getMaxAcquiredBufferCountForCurrentRefreshRate(
+                                          mOwnerUid));
         decrementPendingBufferCount();
     }
 }