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Commit 645b1f7f authored by Andy McFadden's avatar Andy McFadden
Browse files

Replace "lower power mode" experiment 

This replaces the previous low-power mode experiment, which
discarded refresh events, with a new experiment that alters
the refresh period.

(see also I2849e5ea335c0d2509fea1c315392bce7f20451d )

The feature is enabled by specifying a nonzero value for the
"refresh skip count", which indicates the number of periods
to skip.  For example, the command:

  adb shell service call SurfaceFlinger 1016 i32 1

sets a skip count of '1', yielding a 30Hz refresh rate on a device
with a 60Hz display.  Changing the last value to '2' would set the
refresh to 20Hz.  '0' returns to the default behavior.

Bug 15523257

Change-Id: I00039c22a55750e74035644c63800e4bee1c774a
parent 5167ec68

services/surfaceflinger/DispSync.cpp

+22 −27
Original line number Diff line number Diff line
@@ -53,10 +53,7 @@ class DispSyncThread: public Thread { 
public:



    DispSyncThread():

            mLowPowerMode(false),

            mStop(false),

            mLastVsyncSent(false),

            mLastBufferFull(false),

            mPeriod(0),

            mPhase(0),

            mWakeupLatency(0) {
@@ -140,19 +137,8 @@ public: 
            }



            if (callbackInvocations.size() > 0) {

                if (mLowPowerMode) {

                    if (!mLastVsyncSent || !mLastBufferFull) {

                        fireCallbackInvocations(callbackInvocations);

                        mLastVsyncSent = true;

                    } else

                        mLastVsyncSent = false;

                } else {

                fireCallbackInvocations(callbackInvocations);

            }

                mLastBufferFull = true;

            } else {

                mLastBufferFull = false;

            }

        }



        return false;
@@ -205,7 +191,6 @@ public: 
        return !mEventListeners.empty();

    }



    bool mLowPowerMode;

private:



    struct EventListener {
@@ -278,8 +263,6 @@ private: 
    }



    bool mStop;

    bool mLastVsyncSent;

    bool mLastBufferFull;



    nsecs_t mPeriod;

    nsecs_t mPhase;
@@ -304,8 +287,10 @@ private: 
    bool mParity;

};



DispSync::DispSync() {

    mThread = new DispSyncThread();

DispSync::DispSync() :

        mRefreshSkipCount(0),

        mThread(new DispSyncThread()) {



    mThread->run("DispSync", PRIORITY_URGENT_DISPLAY + PRIORITY_MORE_FAVORABLE);



    reset();
@@ -404,8 +389,11 @@ status_t DispSync::addEventListener(nsecs_t phase, 
    return mThread->addEventListener(phase, callback);

}



void DispSync::setLowPowerMode(bool enabled) {

    mThread->mLowPowerMode = enabled;

void DispSync::setRefreshSkipCount(int count) {

    Mutex::Autolock lock(mMutex);

    ALOGD("setRefreshSkipCount(%d)", count);

    mRefreshSkipCount = count;

    updateModelLocked();

}



status_t DispSync::removeEventListener(const sp<Callback>& callback) {
@@ -456,6 +444,9 @@ void DispSync::updateModelLocked() { 
            ATRACE_INT64("DispSync:Phase", mPhase);

        }



        // Artificially inflate the period if requested.

        mPeriod += mPeriod * mRefreshSkipCount;



        mThread->updateModel(mPeriod, mPhase);

    }

}
@@ -465,15 +456,19 @@ void DispSync::updateErrorLocked() { 
        return;

    }



    // Need to compare present fences against the un-adjusted refresh period,

    // since they might arrive between two events.

    nsecs_t period = mPeriod / (1 + mRefreshSkipCount);



    int numErrSamples = 0;

    nsecs_t sqErrSum = 0;



    for (size_t i = 0; i < NUM_PRESENT_SAMPLES; i++) {

        nsecs_t sample = mPresentTimes[i];

        if (sample > mPhase) {

            nsecs_t sampleErr = (sample - mPhase) % mPeriod;

            if (sampleErr > mPeriod / 2) {

                sampleErr -= mPeriod;

            nsecs_t sampleErr = (sample - mPhase) % period;

            if (sampleErr > period / 2) {

                sampleErr -= period;

            }

            sqErrSum += sampleErr * sampleErr;

            numErrSamples++;
@@ -510,8 +505,8 @@ void DispSync::dump(String8& result) const { 
    Mutex::Autolock lock(mMutex);

    result.appendFormat("present fences are %s\n",

            kIgnorePresentFences ? "ignored" : "used");

    result.appendFormat("mPeriod: %" PRId64 " ns (%.3f fps)\n",

            mPeriod, 1000000000.0 / mPeriod);

    result.appendFormat("mPeriod: %" PRId64 " ns (%.3f fps; skipCount=%d)\n",

            mPeriod, 1000000000.0 / mPeriod, mRefreshSkipCount);

    result.appendFormat("mPhase: %" PRId64 " ns\n", mPhase);

    result.appendFormat("mError: %" PRId64 " ns (sqrt=%.1f)\n",

            mError, sqrt(mError));

services/surfaceflinger/DispSync.h

+8 −2
Original line number Diff line number Diff line
@@ -67,6 +67,7 @@ public: 
    DispSync();

    ~DispSync();



    // reset clears the resync samples and error value.

    void reset();



    // addPresentFence adds a fence for use in validating the current vsync
@@ -100,8 +101,11 @@ public: 
    // turned on.  It should NOT be used after that.

    void setPeriod(nsecs_t period);



    // Setting the low power mode reduces the frame rate to half of the default

    void setLowPowerMode(bool enabled);

    // setRefreshSkipCount specifies an additional number of refresh

    // cycles to skip.  For example, on a 60Hz display, a skip count of 1

    // will result in events happening at 30Hz.  Default is zero.  The idea

    // is to sacrifice smoothness for battery life.

    void setRefreshSkipCount(int count);



    // addEventListener registers a callback to be called repeatedly at the

    // given phase offset from the hardware vsync events.  The callback is
@@ -161,6 +165,8 @@ private: 
    nsecs_t mPresentTimes[NUM_PRESENT_SAMPLES];

    size_t mPresentSampleOffset;



    int mRefreshSkipCount;



    // mThread is the thread from which all the callbacks are called.

    sp<DispSyncThread> mThread;

services/surfaceflinger/SurfaceFlinger.cpp

+2 −5
Original line number Diff line number Diff line
@@ -2682,11 +2682,8 @@ status_t SurfaceFlinger::onTransact( 
            // This is an experimental interface

            // Needs to be shifted to proper binder interface when we productize

            case 1016: {

                mPrimaryDispSync.setLowPowerMode(true);

                return NO_ERROR;

            }

            case 1017: {

                mPrimaryDispSync.setLowPowerMode(false);

                n = data.readInt32();

                mPrimaryDispSync.setRefreshSkipCount(n);

                return NO_ERROR;

            }

        }