commit b17c62120b646f378c0b842b3d7fcce8a5540e3e
author Dominik Laskowski <domlaskowski@google.com> Mon May 09 09:36:19 2022 -0700
committer Dominik Laskowski <domlaskowski@google.com> Mon May 16 08:13:29 2022 -0700
tree 13f01098a51f9c387d3e8c87683f55ef40de4ba4
parent bb448ce9aa521f9574d94c9ec2d57eb7d37382cb

FTL: Yield futures without overhead

ftl::yield, which lifts T to std::future<T>, incurs the cost of
allocating, ref counting, and locking the latter's shared state.

Consolidate the existing std::future extensions into ftl::Future,
and optimize ftl::yield by including static storage for T within.

Bug: 232436803
Test: simpleperf (-31% cycles in postFramebuffer)
Change-Id: I9a7ca7de17e7af10515de97d2f6a0dfa24e35d7a

services/surfaceflinger/SurfaceFlinger.h

diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index dc54ac2..52dd418 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -27,6 +27,7 @@
 #include <android/gui/DisplayState.h>
 #include <cutils/atomic.h>
 #include <cutils/compiler.h>
+#include <ftl/future.h>
 #include <ftl/small_map.h>
 #include <gui/BufferQueue.h>
 #include <gui/FrameTimestamps.h>
@@ -77,7 +78,6 @@
 #include <atomic>
 #include <cstdint>
 #include <functional>
-#include <future>
 #include <map>
 #include <memory>
 #include <mutex>
@@ -398,7 +398,7 @@
     using VsyncModulator = scheduler::VsyncModulator;
     using TransactionSchedule = scheduler::TransactionSchedule;
     using TraverseLayersFunction = std::function<void(const LayerVector::Visitor&)>;
-    using RenderAreaFuture = std::future<std::unique_ptr<RenderArea>>;
+    using RenderAreaFuture = ftl::Future<std::unique_ptr<RenderArea>>;
     using DumpArgs = Vector<String16>;
     using Dumper = std::function<void(const DumpArgs&, bool asProto, std::string&)>;
 
@@ -868,15 +868,15 @@
     // Boot animation, on/off animations and screen capture
     void startBootAnim();
 
-    std::shared_future<FenceResult> captureScreenCommon(RenderAreaFuture, TraverseLayersFunction,
-                                                        ui::Size bufferSize, ui::PixelFormat,
-                                                        bool allowProtected, bool grayscale,
-                                                        const sp<IScreenCaptureListener>&);
-    std::shared_future<FenceResult> captureScreenCommon(
+    ftl::SharedFuture<FenceResult> captureScreenCommon(RenderAreaFuture, TraverseLayersFunction,
+                                                       ui::Size bufferSize, ui::PixelFormat,
+                                                       bool allowProtected, bool grayscale,
+                                                       const sp<IScreenCaptureListener>&);
+    ftl::SharedFuture<FenceResult> captureScreenCommon(
             RenderAreaFuture, TraverseLayersFunction,
             const std::shared_ptr<renderengine::ExternalTexture>&, bool regionSampling,
             bool grayscale, const sp<IScreenCaptureListener>&);
-    std::shared_future<FenceResult> renderScreenImpl(
+    ftl::SharedFuture<FenceResult> renderScreenImpl(
             const RenderArea&, TraverseLayersFunction,
             const std::shared_ptr<renderengine::ExternalTexture>&, bool canCaptureBlackoutContent,
             bool regionSampling, bool grayscale, ScreenCaptureResults&) EXCLUDES(mStateLock);