The document discusses analyzing Android application performance using Systrace. Systrace captures timing information about processes and system events. It can show CPU scheduling, graphics rendering, vsync events and more. The document provides examples of using Systrace from the command line and instrumenting code with ATRACE macros to trace custom events and values. Key classes and functions related to vsync, surface flinger, and the framebuffer queue are also outlined.

1. Analyzing Display and
Performance with Systrace
Peter.Pan

2. What is Systrace
• The Systrace tool helps analyze the
performance of your application by capturing
and displaying execution times of your
applications processes and other Android
system processes.

3. Command Line Usage
• Android 4.3 and higher options
$ cd $(project)/extenal/chromium-trace/
$ python systrace.py --time=10 -o mynewtrace.html –b 2048 sched gfx view wm

4. ATRACE
• Path
– frameworks/native/cmds/atrace/atrace.cpp
• Define (form system/core/include/cutils/trace.h)
– #define ATRACE_TAG ATRACE_TAG_GRAPHICS
• Function
– ATRACE_CALL()
• Variables
– ATRACE_INT(“Name”, Value);
– ATRACE_INT64(“Name”, Value64);
#define ATRACE_TAG ATRACE_TAG_GRAPHICS
…
Void Function(){
ATRACE_CALL();
int value = 0;
value = Random();
ATRACE_INT(“RandomValue”, value);
}
…

5. GUI
Finder
CPU infor.
Control bar
Surceflinger
Other processes
Detail
Timeline

6. Operation
Keyword
Shortcut:
W: Zoom In
S: Zoom Out
A: Pan left
D: Pan right

7. CPU Scheduling
• $ python systrace.py --time=10 -o mynewtrace.html sched gfx view wm freq

8. Process status
Status:
*Uninterruptable sleep (usually IO)
*Running or runnable (on run queue)
*sleeping

9. Vsync_On
Add/Remove a listener to DispVsyncSource.

10. Vsync_On
@EventThread.cpp
Vector< sp<EventThread::Connection> EventThread::waitForEvent(…){
…
if (timestamp && !waitForVSync) {
disableVSyncLocked();
} else if (!timestamp && waitForVSync) {
enableVSyncLocked();
}
…
}
@Sufaceflinger.cpp
virtual void setVSyncEnabled(bool enable) {
if (enable) {
status_t err = mDispSync->addEventListener(mPhaseOffset, static_cast<DispSync::Callback*>(this));
…
ATRACE_INT("VsyncOn", 1);
} else {
status_t err = mDispSync->removeEventListener(static_cast<DispSync::Callback*>(this));
…
ATRACE_INT("VsyncOn", 0);
}
}

11. VSYNC
DispVsyncSource produces the Vsync signal.

12. Vsync
@DispSync.cpp
virtual bool threadLoop() {
while (true) {
…
if (callbackInvocations.size() > 0) {
fireCallbackInvocations(callbackInvocations);
}
…
}…
}
@Surfacefliger.cpp
virtual void onDispSyncEvent(nsecs_t when)
{
sp<VSyncSource::Callback> callback;
{
Mutex::Autolock lock(mMutex);
callback = mCallback;
if (mTraceVsync) {
mValue = (mValue + 1) % 2;
ATRACE_INT("VSYNC", mValue);
}
}
if (callback != NULL) {
callback->onVSyncEvent(when);
}
}
@DispSync.cpp
void fireCallbackInvocations(…) {
for (size_t i = 0; i < callbacks.size(); i++) {
callbacks[i].mCallback-
>onDispSyncEvent(callbacks[i].mEventTime);
}
}

13. HW_Vsync0
Need HW Vsync
@HWComposer.cpp
void vsync(int disp, int64_t timestamp) {
…
char tag[16];
snprintf(tag, sizeof(tag), "HW_VSYNC_%1u", disp);
ATRACE_INT(tag, ++mVSyncCounts[disp] & 1);
mEventHandler.onVSyncReceived(disp, timestamp);
…
}

14. HW_Vsync0
@Surfaceflinger.cpp
void surfaceflinger::onVSyncReceived(){
if (type == 0 && mPrimaryHWVsyncEnabled) {
needsHwVsync = mPrimaryDispSync.addResyncSample(timestamp);
}
if (needsHwVsync) {
enableHardwareVsync();
} else {
disableHardwareVsync(false);
}…
}
@Surfaceflinger.cpp
voidsurfaceflinger::onScreenAcquired(){
…
mEventThread->onScreenAcquired();
resyncToHardwareVsync(true); …
}
@Surfaceflinger.cpp
void surfaceflinger:: onScreenReleased(){
…
if (type== DisplayDevice::DISPLAY_PRIMARY) {
disableHardwareVsync(true);
} …
}

15. Sufacefliger
QueueBuffer()

16. DequeueBuffer()/QueueBuffer()
DequeueBuffer() QueueBuffer()

17. QueueBuffer()/AcquirBuffer()
QueueBuffer()
AcquirBuffer()
+1 -1

18. QueueBuffer()/AcquirBuffer()
@BufferQueue.cpp
status_t BufferQueue::acquireBuffer(BufferItem *buffer, nsecs_t expectedPresent)
{
…
ATRACE_INT(mConsumerName.string(), Queue.size());
…
}
@BufferQueue.cpp
status_t BufferQueue::QueueuBuffer(BufferItem *buffer, nsecs_t expectedPresent)
{
…
ATRACE_INT(mConsumerName.string(), Queue.size());
…
}

19. FramebufferSurface
QueueBuffer() AcquirBuffer()

20. Case study(1)
DeliverInputEvent()
Status change
QueueBuffer()

21. Case Study(2)
Animator

22. Case Study(3)

23. Reference
• http://developer.android.com/tools/debugging/systrace.html
• http://www.curious-creature.org/2012/12/01/android-
performance-case-study/