SF: Move relevant scheduler files into one directory.

Scheduler (see go/surface-flinger-scheduler) is going to live in its own
directory. This CL just moves the relevant files into that directory. No
changes to business logic.

Test: all SF tests pass.
Change-Id: Iff0717f9867316b28e68fd8311bd9fdc4e029951
diff --git a/services/surfaceflinger/Scheduler/DispSync.cpp b/services/surfaceflinger/Scheduler/DispSync.cpp
new file mode 100644
index 0000000..9d9acd3
--- /dev/null
+++ b/services/surfaceflinger/Scheduler/DispSync.cpp
@@ -0,0 +1,729 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define ATRACE_TAG ATRACE_TAG_GRAPHICS
+//#define LOG_NDEBUG 0
+
+// This is needed for stdint.h to define INT64_MAX in C++
+#define __STDC_LIMIT_MACROS
+
+#include <math.h>
+
+#include <algorithm>
+
+#include <log/log.h>
+#include <utils/String8.h>
+#include <utils/Thread.h>
+#include <utils/Trace.h>
+
+#include <ui/FenceTime.h>
+
+#include "DispSync.h"
+#include "EventLog/EventLog.h"
+#include "SurfaceFlinger.h"
+
+using std::max;
+using std::min;
+
+namespace android {
+
+DispSync::~DispSync() = default;
+
+namespace impl {
+
+// Setting this to true enables verbose tracing that can be used to debug
+// vsync event model or phase issues.
+static const bool kTraceDetailedInfo = false;
+
+// Setting this to true adds a zero-phase tracer for correlating with hardware
+// vsync events
+static const bool kEnableZeroPhaseTracer = false;
+
+// This is the threshold used to determine when hardware vsync events are
+// needed to re-synchronize the software vsync model with the hardware.  The
+// error metric used is the mean of the squared difference between each
+// present time and the nearest software-predicted vsync.
+static const nsecs_t kErrorThreshold = 160000000000; // 400 usec squared
+
+#undef LOG_TAG
+#define LOG_TAG "DispSyncThread"
+class DispSyncThread : public Thread {
+public:
+    explicit DispSyncThread(const char* name)
+          : mName(name),
+            mStop(false),
+            mPeriod(0),
+            mPhase(0),
+            mReferenceTime(0),
+            mWakeupLatency(0),
+            mFrameNumber(0) {}
+
+    virtual ~DispSyncThread() {}
+
+    void updateModel(nsecs_t period, nsecs_t phase, nsecs_t referenceTime) {
+        if (kTraceDetailedInfo) ATRACE_CALL();
+        Mutex::Autolock lock(mMutex);
+        mPeriod = period;
+        mPhase = phase;
+        mReferenceTime = referenceTime;
+        ALOGV("[%s] updateModel: mPeriod = %" PRId64 ", mPhase = %" PRId64
+              " mReferenceTime = %" PRId64,
+              mName, ns2us(mPeriod), ns2us(mPhase), ns2us(mReferenceTime));
+        mCond.signal();
+    }
+
+    void stop() {
+        if (kTraceDetailedInfo) ATRACE_CALL();
+        Mutex::Autolock lock(mMutex);
+        mStop = true;
+        mCond.signal();
+    }
+
+    virtual bool threadLoop() {
+        status_t err;
+        nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
+
+        while (true) {
+            std::vector<CallbackInvocation> callbackInvocations;
+
+            nsecs_t targetTime = 0;
+
+            { // Scope for lock
+                Mutex::Autolock lock(mMutex);
+
+                if (kTraceDetailedInfo) {
+                    ATRACE_INT64("DispSync:Frame", mFrameNumber);
+                }
+                ALOGV("[%s] Frame %" PRId64, mName, mFrameNumber);
+                ++mFrameNumber;
+
+                if (mStop) {
+                    return false;
+                }
+
+                if (mPeriod == 0) {
+                    err = mCond.wait(mMutex);
+                    if (err != NO_ERROR) {
+                        ALOGE("error waiting for new events: %s (%d)", strerror(-err), err);
+                        return false;
+                    }
+                    continue;
+                }
+
+                targetTime = computeNextEventTimeLocked(now);
+
+                bool isWakeup = false;
+
+                if (now < targetTime) {
+                    if (kTraceDetailedInfo) ATRACE_NAME("DispSync waiting");
+
+                    if (targetTime == INT64_MAX) {
+                        ALOGV("[%s] Waiting forever", mName);
+                        err = mCond.wait(mMutex);
+                    } else {
+                        ALOGV("[%s] Waiting until %" PRId64, mName, ns2us(targetTime));
+                        err = mCond.waitRelative(mMutex, targetTime - now);
+                    }
+
+                    if (err == TIMED_OUT) {
+                        isWakeup = true;
+                    } else if (err != NO_ERROR) {
+                        ALOGE("error waiting for next event: %s (%d)", strerror(-err), err);
+                        return false;
+                    }
+                }
+
+                now = systemTime(SYSTEM_TIME_MONOTONIC);
+
+                // Don't correct by more than 1.5 ms
+                static const nsecs_t kMaxWakeupLatency = us2ns(1500);
+
+                if (isWakeup) {
+                    mWakeupLatency = ((mWakeupLatency * 63) + (now - targetTime)) / 64;
+                    mWakeupLatency = min(mWakeupLatency, kMaxWakeupLatency);
+                    if (kTraceDetailedInfo) {
+                        ATRACE_INT64("DispSync:WakeupLat", now - targetTime);
+                        ATRACE_INT64("DispSync:AvgWakeupLat", mWakeupLatency);
+                    }
+                }
+
+                callbackInvocations = gatherCallbackInvocationsLocked(now);
+            }
+
+            if (callbackInvocations.size() > 0) {
+                fireCallbackInvocations(callbackInvocations);
+            }
+        }
+
+        return false;
+    }
+
+    status_t addEventListener(const char* name, nsecs_t phase, DispSync::Callback* callback) {
+        if (kTraceDetailedInfo) ATRACE_CALL();
+        Mutex::Autolock lock(mMutex);
+
+        for (size_t i = 0; i < mEventListeners.size(); i++) {
+            if (mEventListeners[i].mCallback == callback) {
+                return BAD_VALUE;
+            }
+        }
+
+        EventListener listener;
+        listener.mName = name;
+        listener.mPhase = phase;
+        listener.mCallback = callback;
+
+        // We want to allow the firstmost future event to fire without
+        // allowing any past events to fire
+        listener.mLastEventTime = systemTime() - mPeriod / 2 + mPhase - mWakeupLatency;
+
+        mEventListeners.push_back(listener);
+
+        mCond.signal();
+
+        return NO_ERROR;
+    }
+
+    status_t removeEventListener(DispSync::Callback* callback) {
+        if (kTraceDetailedInfo) ATRACE_CALL();
+        Mutex::Autolock lock(mMutex);
+
+        for (std::vector<EventListener>::iterator it = mEventListeners.begin();
+             it != mEventListeners.end(); ++it) {
+            if (it->mCallback == callback) {
+                mEventListeners.erase(it);
+                mCond.signal();
+                return NO_ERROR;
+            }
+        }
+
+        return BAD_VALUE;
+    }
+
+    status_t changePhaseOffset(DispSync::Callback* callback, nsecs_t phase) {
+        if (kTraceDetailedInfo) ATRACE_CALL();
+        Mutex::Autolock lock(mMutex);
+
+        for (auto& eventListener : mEventListeners) {
+            if (eventListener.mCallback == callback) {
+                const nsecs_t oldPhase = eventListener.mPhase;
+                eventListener.mPhase = phase;
+
+                // Pretend that the last time this event was handled at the same frame but with the
+                // new offset to allow for a seamless offset change without double-firing or
+                // skipping.
+                nsecs_t diff = oldPhase - phase;
+                if (diff > mPeriod / 2) {
+                    diff -= mPeriod;
+                } else if (diff < -mPeriod / 2) {
+                    diff += mPeriod;
+                }
+                eventListener.mLastEventTime -= diff;
+                mCond.signal();
+                return NO_ERROR;
+            }
+        }
+
+        return BAD_VALUE;
+    }
+
+private:
+    struct EventListener {
+        const char* mName;
+        nsecs_t mPhase;
+        nsecs_t mLastEventTime;
+        DispSync::Callback* mCallback;
+    };
+
+    struct CallbackInvocation {
+        DispSync::Callback* mCallback;
+        nsecs_t mEventTime;
+    };
+
+    nsecs_t computeNextEventTimeLocked(nsecs_t now) {
+        if (kTraceDetailedInfo) ATRACE_CALL();
+        ALOGV("[%s] computeNextEventTimeLocked", mName);
+        nsecs_t nextEventTime = INT64_MAX;
+        for (size_t i = 0; i < mEventListeners.size(); i++) {
+            nsecs_t t = computeListenerNextEventTimeLocked(mEventListeners[i], now);
+
+            if (t < nextEventTime) {
+                nextEventTime = t;
+            }
+        }
+
+        ALOGV("[%s] nextEventTime = %" PRId64, mName, ns2us(nextEventTime));
+        return nextEventTime;
+    }
+
+    std::vector<CallbackInvocation> gatherCallbackInvocationsLocked(nsecs_t now) {
+        if (kTraceDetailedInfo) ATRACE_CALL();
+        ALOGV("[%s] gatherCallbackInvocationsLocked @ %" PRId64, mName, ns2us(now));
+
+        std::vector<CallbackInvocation> callbackInvocations;
+        nsecs_t onePeriodAgo = now - mPeriod;
+
+        for (auto& eventListener : mEventListeners) {
+            nsecs_t t = computeListenerNextEventTimeLocked(eventListener, onePeriodAgo);
+
+            if (t < now) {
+                CallbackInvocation ci;
+                ci.mCallback = eventListener.mCallback;
+                ci.mEventTime = t;
+                ALOGV("[%s] [%s] Preparing to fire", mName, eventListener.mName);
+                callbackInvocations.push_back(ci);
+                eventListener.mLastEventTime = t;
+            }
+        }
+
+        return callbackInvocations;
+    }
+
+    nsecs_t computeListenerNextEventTimeLocked(const EventListener& listener, nsecs_t baseTime) {
+        if (kTraceDetailedInfo) ATRACE_CALL();
+        ALOGV("[%s] [%s] computeListenerNextEventTimeLocked(%" PRId64 ")", mName, listener.mName,
+              ns2us(baseTime));
+
+        nsecs_t lastEventTime = listener.mLastEventTime + mWakeupLatency;
+        ALOGV("[%s] lastEventTime: %" PRId64, mName, ns2us(lastEventTime));
+        if (baseTime < lastEventTime) {
+            baseTime = lastEventTime;
+            ALOGV("[%s] Clamping baseTime to lastEventTime -> %" PRId64, mName, ns2us(baseTime));
+        }
+
+        baseTime -= mReferenceTime;
+        ALOGV("[%s] Relative baseTime = %" PRId64, mName, ns2us(baseTime));
+        nsecs_t phase = mPhase + listener.mPhase;
+        ALOGV("[%s] Phase = %" PRId64, mName, ns2us(phase));
+        baseTime -= phase;
+        ALOGV("[%s] baseTime - phase = %" PRId64, mName, ns2us(baseTime));
+
+        // If our previous time is before the reference (because the reference
+        // has since been updated), the division by mPeriod will truncate
+        // towards zero instead of computing the floor. Since in all cases
+        // before the reference we want the next time to be effectively now, we
+        // set baseTime to -mPeriod so that numPeriods will be -1.
+        // When we add 1 and the phase, we will be at the correct event time for
+        // this period.
+        if (baseTime < 0) {
+            ALOGV("[%s] Correcting negative baseTime", mName);
+            baseTime = -mPeriod;
+        }
+
+        nsecs_t numPeriods = baseTime / mPeriod;
+        ALOGV("[%s] numPeriods = %" PRId64, mName, numPeriods);
+        nsecs_t t = (numPeriods + 1) * mPeriod + phase;
+        ALOGV("[%s] t = %" PRId64, mName, ns2us(t));
+        t += mReferenceTime;
+        ALOGV("[%s] Absolute t = %" PRId64, mName, ns2us(t));
+
+        // Check that it's been slightly more than half a period since the last
+        // event so that we don't accidentally fall into double-rate vsyncs
+        if (t - listener.mLastEventTime < (3 * mPeriod / 5)) {
+            t += mPeriod;
+            ALOGV("[%s] Modifying t -> %" PRId64, mName, ns2us(t));
+        }
+
+        t -= mWakeupLatency;
+        ALOGV("[%s] Corrected for wakeup latency -> %" PRId64, mName, ns2us(t));
+
+        return t;
+    }
+
+    void fireCallbackInvocations(const std::vector<CallbackInvocation>& callbacks) {
+        if (kTraceDetailedInfo) ATRACE_CALL();
+        for (size_t i = 0; i < callbacks.size(); i++) {
+            callbacks[i].mCallback->onDispSyncEvent(callbacks[i].mEventTime);
+        }
+    }
+
+    const char* const mName;
+
+    bool mStop;
+
+    nsecs_t mPeriod;
+    nsecs_t mPhase;
+    nsecs_t mReferenceTime;
+    nsecs_t mWakeupLatency;
+
+    int64_t mFrameNumber;
+
+    std::vector<EventListener> mEventListeners;
+
+    Mutex mMutex;
+    Condition mCond;
+};
+
+#undef LOG_TAG
+#define LOG_TAG "DispSync"
+
+class ZeroPhaseTracer : public DispSync::Callback {
+public:
+    ZeroPhaseTracer() : mParity(false) {}
+
+    virtual void onDispSyncEvent(nsecs_t /*when*/) {
+        mParity = !mParity;
+        ATRACE_INT("ZERO_PHASE_VSYNC", mParity ? 1 : 0);
+    }
+
+private:
+    bool mParity;
+};
+
+DispSync::DispSync(const char* name)
+      : mName(name), mRefreshSkipCount(0), mThread(new DispSyncThread(name)) {}
+
+DispSync::~DispSync() {}
+
+void DispSync::init(bool hasSyncFramework, int64_t dispSyncPresentTimeOffset) {
+    mIgnorePresentFences = !hasSyncFramework;
+    mPresentTimeOffset = dispSyncPresentTimeOffset;
+    mThread->run("DispSync", PRIORITY_URGENT_DISPLAY + PRIORITY_MORE_FAVORABLE);
+
+    // set DispSync to SCHED_FIFO to minimize jitter
+    struct sched_param param = {0};
+    param.sched_priority = 2;
+    if (sched_setscheduler(mThread->getTid(), SCHED_FIFO, &param) != 0) {
+        ALOGE("Couldn't set SCHED_FIFO for DispSyncThread");
+    }
+
+    reset();
+    beginResync();
+
+    if (kTraceDetailedInfo && kEnableZeroPhaseTracer) {
+        mZeroPhaseTracer = std::make_unique<ZeroPhaseTracer>();
+        addEventListener("ZeroPhaseTracer", 0, mZeroPhaseTracer.get());
+    }
+}
+
+void DispSync::reset() {
+    Mutex::Autolock lock(mMutex);
+    resetLocked();
+}
+
+void DispSync::resetLocked() {
+    mPhase = 0;
+    mReferenceTime = 0;
+    mModelUpdated = false;
+    mNumResyncSamples = 0;
+    mFirstResyncSample = 0;
+    mNumResyncSamplesSincePresent = 0;
+    resetErrorLocked();
+}
+
+bool DispSync::addPresentFence(const std::shared_ptr<FenceTime>& fenceTime) {
+    Mutex::Autolock lock(mMutex);
+
+    if (mIgnorePresentFences) {
+        return true;
+    }
+
+    mPresentFences[mPresentSampleOffset] = fenceTime;
+    mPresentSampleOffset = (mPresentSampleOffset + 1) % NUM_PRESENT_SAMPLES;
+    mNumResyncSamplesSincePresent = 0;
+
+    updateErrorLocked();
+
+    return !mModelUpdated || mError > kErrorThreshold;
+}
+
+void DispSync::beginResync() {
+    Mutex::Autolock lock(mMutex);
+    ALOGV("[%s] beginResync", mName);
+    mModelUpdated = false;
+    mNumResyncSamples = 0;
+}
+
+bool DispSync::addResyncSample(nsecs_t timestamp) {
+    Mutex::Autolock lock(mMutex);
+
+    ALOGV("[%s] addResyncSample(%" PRId64 ")", mName, ns2us(timestamp));
+
+    size_t idx = (mFirstResyncSample + mNumResyncSamples) % MAX_RESYNC_SAMPLES;
+    mResyncSamples[idx] = timestamp;
+    if (mNumResyncSamples == 0) {
+        mPhase = 0;
+        mReferenceTime = timestamp;
+        ALOGV("[%s] First resync sample: mPeriod = %" PRId64 ", mPhase = 0, "
+              "mReferenceTime = %" PRId64,
+              mName, ns2us(mPeriod), ns2us(mReferenceTime));
+        mThread->updateModel(mPeriod, mPhase, mReferenceTime);
+    }
+
+    if (mNumResyncSamples < MAX_RESYNC_SAMPLES) {
+        mNumResyncSamples++;
+    } else {
+        mFirstResyncSample = (mFirstResyncSample + 1) % MAX_RESYNC_SAMPLES;
+    }
+
+    updateModelLocked();
+
+    if (mNumResyncSamplesSincePresent++ > MAX_RESYNC_SAMPLES_WITHOUT_PRESENT) {
+        resetErrorLocked();
+    }
+
+    if (mIgnorePresentFences) {
+        // If we're ignoring the present fences we have no way to know whether
+        // or not we're synchronized with the HW vsyncs, so we just request
+        // that the HW vsync events be turned on.
+        return true;
+    }
+
+    // Check against kErrorThreshold / 2 to add some hysteresis before having to
+    // resync again
+    bool modelLocked = mModelUpdated && mError < (kErrorThreshold / 2);
+    ALOGV("[%s] addResyncSample returning %s", mName, modelLocked ? "locked" : "unlocked");
+    return !modelLocked;
+}
+
+void DispSync::endResync() {}
+
+status_t DispSync::addEventListener(const char* name, nsecs_t phase, Callback* callback) {
+    Mutex::Autolock lock(mMutex);
+    return mThread->addEventListener(name, phase, callback);
+}
+
+void DispSync::setRefreshSkipCount(int count) {
+    Mutex::Autolock lock(mMutex);
+    ALOGD("setRefreshSkipCount(%d)", count);
+    mRefreshSkipCount = count;
+    updateModelLocked();
+}
+
+status_t DispSync::removeEventListener(Callback* callback) {
+    Mutex::Autolock lock(mMutex);
+    return mThread->removeEventListener(callback);
+}
+
+status_t DispSync::changePhaseOffset(Callback* callback, nsecs_t phase) {
+    Mutex::Autolock lock(mMutex);
+    return mThread->changePhaseOffset(callback, phase);
+}
+
+void DispSync::setPeriod(nsecs_t period) {
+    Mutex::Autolock lock(mMutex);
+    mPeriodBase = mPeriod = period;
+    mPhase = 0;
+    mReferenceTime = 0;
+    mThread->updateModel(mPeriod, mPhase, mReferenceTime);
+}
+
+void DispSync::scalePeriod(uint32_t multiplier, uint32_t divisor) {
+    Mutex::Autolock lock(mMutex);
+
+    // if only 1 of the properties is updated, we will get to this
+    // point "attempting" to set the scale to 1 when it is already
+    // 1.  Check that special case so that we don't do a useless
+    // update of the model.
+    if ((multiplier == 1) && (divisor == 1) && (mPeriod == mPeriodBase)) return;
+
+    mPeriod = mPeriodBase * multiplier / divisor;
+    mThread->updateModel(mPeriod, mPhase, mReferenceTime);
+}
+
+nsecs_t DispSync::getPeriod() {
+    // lock mutex as mPeriod changes multiple times in updateModelLocked
+    Mutex::Autolock lock(mMutex);
+    return mPeriod;
+}
+
+void DispSync::updateModelLocked() {
+    ALOGV("[%s] updateModelLocked %zu", mName, mNumResyncSamples);
+    if (mNumResyncSamples >= MIN_RESYNC_SAMPLES_FOR_UPDATE) {
+        ALOGV("[%s] Computing...", mName);
+        nsecs_t durationSum = 0;
+        nsecs_t minDuration = INT64_MAX;
+        nsecs_t maxDuration = 0;
+        for (size_t i = 1; i < mNumResyncSamples; i++) {
+            size_t idx = (mFirstResyncSample + i) % MAX_RESYNC_SAMPLES;
+            size_t prev = (idx + MAX_RESYNC_SAMPLES - 1) % MAX_RESYNC_SAMPLES;
+            nsecs_t duration = mResyncSamples[idx] - mResyncSamples[prev];
+            durationSum += duration;
+            minDuration = min(minDuration, duration);
+            maxDuration = max(maxDuration, duration);
+        }
+
+        // Exclude the min and max from the average
+        durationSum -= minDuration + maxDuration;
+        mPeriodBase = mPeriod = durationSum / (mNumResyncSamples - 3);
+
+        ALOGV("[%s] mPeriod = %" PRId64, mName, ns2us(mPeriod));
+
+        double sampleAvgX = 0;
+        double sampleAvgY = 0;
+        double scale = 2.0 * M_PI / double(mPeriod);
+        // Intentionally skip the first sample
+        for (size_t i = 1; i < mNumResyncSamples; i++) {
+            size_t idx = (mFirstResyncSample + i) % MAX_RESYNC_SAMPLES;
+            nsecs_t sample = mResyncSamples[idx] - mReferenceTime;
+            double samplePhase = double(sample % mPeriod) * scale;
+            sampleAvgX += cos(samplePhase);
+            sampleAvgY += sin(samplePhase);
+        }
+
+        sampleAvgX /= double(mNumResyncSamples - 1);
+        sampleAvgY /= double(mNumResyncSamples - 1);
+
+        mPhase = nsecs_t(atan2(sampleAvgY, sampleAvgX) / scale);
+
+        ALOGV("[%s] mPhase = %" PRId64, mName, ns2us(mPhase));
+
+        if (mPhase < -(mPeriod / 2)) {
+            mPhase += mPeriod;
+            ALOGV("[%s] Adjusting mPhase -> %" PRId64, mName, ns2us(mPhase));
+        }
+
+        if (kTraceDetailedInfo) {
+            ATRACE_INT64("DispSync:Period", mPeriod);
+            ATRACE_INT64("DispSync:Phase", mPhase + mPeriod / 2);
+        }
+
+        // Artificially inflate the period if requested.
+        mPeriod += mPeriod * mRefreshSkipCount;
+
+        mThread->updateModel(mPeriod, mPhase, mReferenceTime);
+        mModelUpdated = true;
+    }
+}
+
+void DispSync::updateErrorLocked() {
+    if (!mModelUpdated) {
+        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++) {
+        // Only check for the cached value of signal time to avoid unecessary
+        // syscalls. It is the responsibility of the DispSync owner to
+        // call getSignalTime() periodically so the cache is updated when the
+        // fence signals.
+        nsecs_t time = mPresentFences[i]->getCachedSignalTime();
+        if (time == Fence::SIGNAL_TIME_PENDING || time == Fence::SIGNAL_TIME_INVALID) {
+            continue;
+        }
+
+        nsecs_t sample = time - mReferenceTime;
+        if (sample <= mPhase) {
+            continue;
+        }
+
+        nsecs_t sampleErr = (sample - mPhase) % period;
+        if (sampleErr > period / 2) {
+            sampleErr -= period;
+        }
+        sqErrSum += sampleErr * sampleErr;
+        numErrSamples++;
+    }
+
+    if (numErrSamples > 0) {
+        mError = sqErrSum / numErrSamples;
+        mZeroErrSamplesCount = 0;
+    } else {
+        mError = 0;
+        // Use mod ACCEPTABLE_ZERO_ERR_SAMPLES_COUNT to avoid log spam.
+        mZeroErrSamplesCount++;
+        ALOGE_IF((mZeroErrSamplesCount % ACCEPTABLE_ZERO_ERR_SAMPLES_COUNT) == 0,
+                 "No present times for model error.");
+    }
+
+    if (kTraceDetailedInfo) {
+        ATRACE_INT64("DispSync:Error", mError);
+    }
+}
+
+void DispSync::resetErrorLocked() {
+    mPresentSampleOffset = 0;
+    mError = 0;
+    mZeroErrSamplesCount = 0;
+    for (size_t i = 0; i < NUM_PRESENT_SAMPLES; i++) {
+        mPresentFences[i] = FenceTime::NO_FENCE;
+    }
+}
+
+nsecs_t DispSync::computeNextRefresh(int periodOffset) const {
+    Mutex::Autolock lock(mMutex);
+    nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
+    nsecs_t phase = mReferenceTime + mPhase;
+    return (((now - phase) / mPeriod) + periodOffset + 1) * mPeriod + phase;
+}
+
+void DispSync::setIgnorePresentFences(bool ignore) {
+    Mutex::Autolock lock(mMutex);
+    if (mIgnorePresentFences != ignore) {
+        mIgnorePresentFences = ignore;
+        resetLocked();
+    }
+}
+
+void DispSync::dump(String8& result) const {
+    Mutex::Autolock lock(mMutex);
+    result.appendFormat("present fences are %s\n", mIgnorePresentFences ? "ignored" : "used");
+    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));
+    result.appendFormat("mNumResyncSamplesSincePresent: %d (limit %d)\n",
+                        mNumResyncSamplesSincePresent, MAX_RESYNC_SAMPLES_WITHOUT_PRESENT);
+    result.appendFormat("mNumResyncSamples: %zd (max %d)\n", mNumResyncSamples, MAX_RESYNC_SAMPLES);
+
+    result.appendFormat("mResyncSamples:\n");
+    nsecs_t previous = -1;
+    for (size_t i = 0; i < mNumResyncSamples; i++) {
+        size_t idx = (mFirstResyncSample + i) % MAX_RESYNC_SAMPLES;
+        nsecs_t sampleTime = mResyncSamples[idx];
+        if (i == 0) {
+            result.appendFormat("  %" PRId64 "\n", sampleTime);
+        } else {
+            result.appendFormat("  %" PRId64 " (+%" PRId64 ")\n", sampleTime,
+                                sampleTime - previous);
+        }
+        previous = sampleTime;
+    }
+
+    result.appendFormat("mPresentFences [%d]:\n", NUM_PRESENT_SAMPLES);
+    nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
+    previous = Fence::SIGNAL_TIME_INVALID;
+    for (size_t i = 0; i < NUM_PRESENT_SAMPLES; i++) {
+        size_t idx = (i + mPresentSampleOffset) % NUM_PRESENT_SAMPLES;
+        nsecs_t presentTime = mPresentFences[idx]->getSignalTime();
+        if (presentTime == Fence::SIGNAL_TIME_PENDING) {
+            result.appendFormat("  [unsignaled fence]\n");
+        } else if (presentTime == Fence::SIGNAL_TIME_INVALID) {
+            result.appendFormat("  [invalid fence]\n");
+        } else if (previous == Fence::SIGNAL_TIME_PENDING ||
+                   previous == Fence::SIGNAL_TIME_INVALID) {
+            result.appendFormat("  %" PRId64 "  (%.3f ms ago)\n", presentTime,
+                                (now - presentTime) / 1000000.0);
+        } else {
+            result.appendFormat("  %" PRId64 " (+%" PRId64 " / %.3f)  (%.3f ms ago)\n", presentTime,
+                                presentTime - previous, (presentTime - previous) / (double)mPeriod,
+                                (now - presentTime) / 1000000.0);
+        }
+        previous = presentTime;
+    }
+
+    result.appendFormat("current monotonic time: %" PRId64 "\n", now);
+}
+
+} // namespace impl
+
+} // namespace android