hwc: fix incorrect wait
bug: 146071486
Previously, we always waited for vsyncPeriod regardless of whether
we actually shouldn't based on the current time and phase matching.
This CL makes our vsyncs closer to being evenly spaced by vsync
interval, through measuring how much time until the next vsync interval
and waiting only that long.
Based on SynctheticWaitVBlank from drm_hwcomposer:
https://cs.corp.google.com/android/external/drm_hwcomposer/drm/vsyncworker.cpp?g=0&l=68
Change-Id: I316efd4ac317e4603ca5bbdf738654c0cd66b91f
diff --git a/system/hwc2/EmuHWC2.cpp b/system/hwc2/EmuHWC2.cpp
index 89d95c8..2d9430f 100644
--- a/system/hwc2/EmuHWC2.cpp
+++ b/system/hwc2/EmuHWC2.cpp
@@ -1391,7 +1391,6 @@
return output;
}
-
// VsyncThread function
bool EmuHWC2::Display::VsyncThread::threadLoop() {
struct timespec rt;
@@ -1402,22 +1401,42 @@
}
const int logInterval = 60;
int64_t lastLogged = rt.tv_sec;
+ int64_t phaseOffset = 0;
int sent = 0;
int lastSent = 0;
bool vsyncEnabled = false;
+
struct timespec wait_time;
wait_time.tv_sec = 0;
wait_time.tv_nsec = mDisplay.mVsyncPeriod;
+ const int64_t kOneRefreshNs = mDisplay.mVsyncPeriod;
+ const int64_t kOneSecondNs = 1000ULL * 1000ULL * 1000ULL;
+ int64_t lastTimeNs = -1;
+ int64_t phasedWaitNs = 0;
+ int64_t currentNs = 0;
while (true) {
- int err = nanosleep(&wait_time, NULL);
- if (err == -1) {
- if (errno == EINTR) {
- break;
- }
- ALOGE("%s: error in vsync thread: %s", __FUNCTION__, strerror(errno));
+ clock_gettime(CLOCK_MONOTONIC, &rt);
+ currentNs = rt.tv_nsec + rt.tv_sec * kOneSecondNs;
+
+ if (lastTimeNs < 0) {
+ phasedWaitNs = currentNs + kOneRefreshNs;
+ } else {
+ phasedWaitNs = kOneRefreshNs *
+ (( currentNs - lastTimeNs) / kOneRefreshNs + 1) +
+ lastTimeNs;
}
+ wait_time.tv_sec = phasedWaitNs / kOneSecondNs;
+ wait_time.tv_nsec = phasedWaitNs - wait_time.tv_sec * kOneSecondNs;
+
+ int ret;
+ do {
+ ret = clock_nanosleep(CLOCK_MONOTONIC, TIMER_ABSTIME, &wait_time, NULL);
+ } while (ret == -1 && errno == EINTR);
+
+ lastTimeNs = phasedWaitNs;
+
std::unique_lock<std::mutex> lock(mDisplay.mStateMutex);
vsyncEnabled = (mDisplay.mVsyncEnabled == Vsync::Enable);
lock.unlock();
@@ -1426,20 +1445,13 @@
continue;
}
- if (clock_gettime(CLOCK_MONOTONIC, &rt) == -1) {
- ALOGE("%s: error in vsync thread clock_gettime: %s",
- __FUNCTION__, strerror(errno));
- }
-
- int64_t timestamp = int64_t(rt.tv_sec) * 1e9 + rt.tv_nsec;
-
lock.lock();
const auto& callbackInfo = mDisplay.mDevice.mCallbacks[Callback::Vsync];
auto vsync = reinterpret_cast<HWC2_PFN_VSYNC>(callbackInfo.pointer);
lock.unlock();
if (vsync) {
- vsync(callbackInfo.data, mDisplay.mId, timestamp);
+ vsync(callbackInfo.data, mDisplay.mId, lastTimeNs);
}
if (rt.tv_sec - lastLogged >= logInterval) {
