Merge "Revert "support work chain in pulled atoms"" (e3b92ab6) · Commits · e / os / android_frameworks_base

cmds/statsd/src/external/StatsCompanionServicePuller.cpp

+1 −1

Original line number	Diff line number	Diff line
		@@ -59,7 +59,7 @@ bool StatsCompanionServicePuller::PullInternal(vector<shared_ptr<LogEvent> >* da
		}
		data->clear();
		for (const StatsLogEventWrapper& it : returned_value) {
		LogEvent::createLogEvents(it, *data);
		data->push_back(make_shared<LogEvent>(it));
		}
		VLOG("StatsCompanionServicePuller::pull succeeded for %d", mTagId);
		return true;

cmds/statsd/src/external/StatsPuller.cpp

+3 −4

Original line number	Diff line number	Diff line
		@@ -32,10 +32,9 @@ using std::lock_guard;
		sp<UidMap> StatsPuller::mUidMap = nullptr;
		void StatsPuller::SetUidMap(const sp<UidMap>& uidMap) { mUidMap = uidMap; }

		// ValueMetric has a minimum bucket size of 10min so that we don't pull too frequently
		StatsPuller::StatsPuller(const int tagId)
		: mTagId(tagId) {
		// Pullers can cause significant impact to system health and battery.
		// So that we don't pull too frequently.
		mCoolDownNs = StatsPullerManager::kAllPullAtomInfo.find(tagId)->second.coolDownNs;
		VLOG("Puller for tag %d created. Cooldown set to %lld", mTagId, (long long)mCoolDownNs);
		}
		@@ -65,7 +64,7 @@ bool StatsPuller::Pull(const int64_t elapsedTimeNs, std::vector<std::shared_ptr<
		data->setLogdWallClockTimestampNs(wallClockTimeNs);
		}
		if (ret && mCachedData.size() > 0) {
		mapAndMergeIsolatedUidsToHostUid(mCachedData, mUidMap, mTagId);
		mergeIsolatedUidsToHostUid(mCachedData, mUidMap, mTagId);
		(*data) = mCachedData;
		}
		StatsdStats::getInstance().notePullDelay(mTagId, getElapsedRealtimeNs() - elapsedTimeNs);

cmds/statsd/src/external/StatsPullerManager.cpp

+66 −29

Original line number	Diff line number	Diff line
		@@ -54,42 +54,52 @@ const std::map<int, PullAtomInfo> StatsPullerManager::kAllPullAtomInfo = {
		// wifi_bytes_transfer
		{android::util::WIFI_BYTES_TRANSFER,
		{{2, 3, 4, 5},
		{},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::WIFI_BYTES_TRANSFER)}},
		// wifi_bytes_transfer_by_fg_bg
		{android::util::WIFI_BYTES_TRANSFER_BY_FG_BG,
		{{3, 4, 5, 6},
		{2},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::WIFI_BYTES_TRANSFER_BY_FG_BG)}},
		// mobile_bytes_transfer
		{android::util::MOBILE_BYTES_TRANSFER,
		{{2, 3, 4, 5},
		{},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::MOBILE_BYTES_TRANSFER)}},
		// mobile_bytes_transfer_by_fg_bg
		{android::util::MOBILE_BYTES_TRANSFER_BY_FG_BG,
		{{3, 4, 5, 6},
		{2},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::MOBILE_BYTES_TRANSFER_BY_FG_BG)}},
		// bluetooth_bytes_transfer
		{android::util::BLUETOOTH_BYTES_TRANSFER,
		{{2, 3},
		{},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::BLUETOOTH_BYTES_TRANSFER)}},
		// kernel_wakelock
		{android::util::KERNEL_WAKELOCK,
		{{}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::KERNEL_WAKELOCK)}},
		{{}, {}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::KERNEL_WAKELOCK)}},
		// subsystem_sleep_state
		{android::util::SUBSYSTEM_SLEEP_STATE,
		{{}, 1 * NS_PER_SEC, new SubsystemSleepStatePuller()}},
		{{}, {}, 1 * NS_PER_SEC, new SubsystemSleepStatePuller()}},
		// on_device_power_measurement
		{android::util::ON_DEVICE_POWER_MEASUREMENT, {{}, 1 * NS_PER_SEC, new PowerStatsPuller()}},
		{android::util::ON_DEVICE_POWER_MEASUREMENT,
		{{}, {}, 1 * NS_PER_SEC, new PowerStatsPuller()}},
		// cpu_time_per_freq
		{android::util::CPU_TIME_PER_FREQ,
		{{3}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::CPU_TIME_PER_FREQ)}},
		{{3},
		{2},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::CPU_TIME_PER_FREQ)}},
		// cpu_time_per_uid
		{android::util::CPU_TIME_PER_UID,
		{{2, 3},
		{},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::CPU_TIME_PER_UID)}},
		// cpu_time_per_uid_freq
		@@ -97,135 +107,162 @@ const std::map<int, PullAtomInfo> StatsPullerManager::kAllPullAtomInfo = {
		// frameworks/base/core/java/com/android/internal/os/KernelCpuProcReader
		{android::util::CPU_TIME_PER_UID_FREQ,
		{{4},
		{2, 3},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::CPU_TIME_PER_UID_FREQ)}},
		// cpu_active_time
		// the throttling is 3sec, handled in
		// frameworks/base/core/java/com/android/internal/os/KernelCpuProcReader
		{android::util::CPU_ACTIVE_TIME,
		{{2}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::CPU_ACTIVE_TIME)}},
		{{2},
		{},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::CPU_ACTIVE_TIME)}},
		// cpu_cluster_time
		// the throttling is 3sec, handled in
		// frameworks/base/core/java/com/android/internal/os/KernelCpuProcReader
		{android::util::CPU_CLUSTER_TIME,
		{{3}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::CPU_CLUSTER_TIME)}},
		{{3},
		{2},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::CPU_CLUSTER_TIME)}},
		// wifi_activity_energy_info
		{android::util::WIFI_ACTIVITY_INFO,
		{{}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::WIFI_ACTIVITY_INFO)}},
		{{},
		{},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::WIFI_ACTIVITY_INFO)}},
		// modem_activity_info
		{android::util::MODEM_ACTIVITY_INFO,
		{{}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::MODEM_ACTIVITY_INFO)}},
		{{},
		{},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::MODEM_ACTIVITY_INFO)}},
		// bluetooth_activity_info
		{android::util::BLUETOOTH_ACTIVITY_INFO,
		{{},
		{},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::BLUETOOTH_ACTIVITY_INFO)}},
		// system_elapsed_realtime
		{android::util::SYSTEM_ELAPSED_REALTIME,
		{{},
		{},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::SYSTEM_ELAPSED_REALTIME)}},
		// system_uptime
		{android::util::SYSTEM_UPTIME,
		{{}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::SYSTEM_UPTIME)}},
		{{}, {}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::SYSTEM_UPTIME)}},
		// remaining_battery_capacity
		{android::util::REMAINING_BATTERY_CAPACITY,
		{{},
		{},
		1 * NS_PER_SEC,
		new ResourceHealthManagerPuller(android::util::REMAINING_BATTERY_CAPACITY)}},
		// full_battery_capacity
		{android::util::FULL_BATTERY_CAPACITY,
		{{},
		{},
		1 * NS_PER_SEC,
		new ResourceHealthManagerPuller(android::util::FULL_BATTERY_CAPACITY)}},
		// battery_voltage
		{android::util::BATTERY_VOLTAGE,
		{{}, 1 * NS_PER_SEC, new ResourceHealthManagerPuller(android::util::BATTERY_VOLTAGE)}},
		// battery_level
		{{}, {}, 1 * NS_PER_SEC, new ResourceHealthManagerPuller(android::util::BATTERY_VOLTAGE)}},
		// battery_voltage
		{android::util::BATTERY_LEVEL,
		{{}, 1 * NS_PER_SEC, new ResourceHealthManagerPuller(android::util::BATTERY_LEVEL)}},
		{{}, {}, 1 * NS_PER_SEC, new ResourceHealthManagerPuller(android::util::BATTERY_LEVEL)}},
		// process_memory_state
		{android::util::PROCESS_MEMORY_STATE,
		{{4, 5, 6, 7, 8, 9},
		{2, 3, 10},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::PROCESS_MEMORY_STATE)}},
		// native_process_memory_state
		{android::util::NATIVE_PROCESS_MEMORY_STATE,
		{{3, 4, 5, 6},
		{2, 7},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::NATIVE_PROCESS_MEMORY_STATE)}},
		{android::util::PROCESS_MEMORY_HIGH_WATER_MARK,
		{{3},
		{2},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::PROCESS_MEMORY_HIGH_WATER_MARK)}},
		// temperature
		{android::util::TEMPERATURE, {{}, 1 * NS_PER_SEC, new ResourceThermalManagerPuller()}},
		{android::util::TEMPERATURE, {{}, {}, 1 * NS_PER_SEC, new ResourceThermalManagerPuller()}},
		// binder_calls
		{android::util::BINDER_CALLS,
		{{4, 5, 6, 8, 12},
		{2, 3, 7, 9, 10, 11, 13},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::BINDER_CALLS)}},
		// binder_calls_exceptions
		{android::util::BINDER_CALLS_EXCEPTIONS,
		{{},
		{},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::BINDER_CALLS_EXCEPTIONS)}},
		// looper_stats
		{android::util::LOOPER_STATS,
		{{5, 6, 7, 8, 9},
		{2, 3, 4, 10},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::LOOPER_STATS)}},
		// Disk Stats
		{android::util::DISK_STATS,
		{{}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::DISK_STATS)}},
		{{}, {}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::DISK_STATS)}},
		// Directory usage
		{android::util::DIRECTORY_USAGE,
		{{}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::DIRECTORY_USAGE)}},
		{{}, {}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::DIRECTORY_USAGE)}},
		// Size of app's code, data, and cache
		{android::util::APP_SIZE,
		{{}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::APP_SIZE)}},
		{{}, {}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::APP_SIZE)}},
		// Size of specific categories of files. Eg. Music.
		{android::util::CATEGORY_SIZE,
		{{}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::CATEGORY_SIZE)}},
		{{}, {}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::CATEGORY_SIZE)}},
		// Number of fingerprints registered to each user.
		{android::util::NUM_FINGERPRINTS,
		{{}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::NUM_FINGERPRINTS)}},
		{{},
		{},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::NUM_FINGERPRINTS)}},
		// ProcStats.
		{android::util::PROC_STATS,
		{{}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::PROC_STATS)}},
		{{}, {}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::PROC_STATS)}},
		// ProcStatsPkgProc.
		{android::util::PROC_STATS_PKG_PROC,
		{{}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::PROC_STATS_PKG_PROC)}},
		{{}, {}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::PROC_STATS_PKG_PROC)}},
		// Disk I/O stats per uid.
		{android::util::DISK_IO,
		{{2,3,4,5,6,7,8,9,10,11},
		{},
		3 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::DISK_IO)}},
		// PowerProfile constants for power model calculations.
		{android::util::POWER_PROFILE,
		{{}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::POWER_PROFILE)}},
		{{}, {}, 1 * NS_PER_SEC, new StatsCompanionServicePuller(android::util::POWER_PROFILE)}},
		// Process cpu stats. Min cool-down is 5 sec, inline with what AcitivityManagerService uses.
		{android::util::PROCESS_CPU_TIME,
		{{} /* additive fields */,
		{{} /* additive fields /, {} / non additive fields */,
		5 * NS_PER_SEC /* min cool-down in seconds*/,
		new StatsCompanionServicePuller(android::util::PROCESS_CPU_TIME)}},
		{android::util::CPU_TIME_PER_THREAD_FREQ,
		{{7},
		{2, 3, 4, 5, 6},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::CPU_TIME_PER_THREAD_FREQ)}},
		// DeviceCalculatedPowerUse.
		{android::util::DEVICE_CALCULATED_POWER_USE,
		{{},
		1 * NS_PER_SEC,
		{{}, {}, 1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::DEVICE_CALCULATED_POWER_USE)}},
		// DeviceCalculatedPowerBlameUid.
		{android::util::DEVICE_CALCULATED_POWER_BLAME_UID,
		{{}, // BatteryStats already merged isolated with host ids so it's unnecessary here.
		{{}, {}, // BatteryStats already merged isolated with host ids so it's unnecessary here.
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::DEVICE_CALCULATED_POWER_BLAME_UID)}},
		// DeviceCalculatedPowerBlameOther.
		{android::util::DEVICE_CALCULATED_POWER_BLAME_OTHER,
		{{},
		{{}, {},
		1 * NS_PER_SEC,
		new StatsCompanionServicePuller(android::util::DEVICE_CALCULATED_POWER_BLAME_OTHER)}},
		// BuildInformation.

cmds/statsd/src/external/StatsPullerManager.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -36,6 +36,9 @@ typedef struct {
		// The field numbers of the fields that need to be summed when merging
		// isolated uid with host uid.
		std::vector<int> additiveFields;
		// The field numbers of the fields that can't be merged when merging
		// data belong to isolated uid and host uid.
		std::vector<int> nonAdditiveFields;
		// How long should the puller wait before doing an actual pull again. Default
		// 1 sec. Set this to 0 if this is handled elsewhere.
		int64_t coolDownNs = 1 * NS_PER_SEC;

cmds/statsd/src/external/puller_util.cpp

+98 −98

Original line number	Diff line number	Diff line
		@@ -25,13 +25,67 @@ namespace android {
		namespace os {
		namespace statsd {

		using std::list;
		using std::map;
		using std::set;
		using std::shared_ptr;
		using std::sort;
		using std::vector;

		namespace {
		bool shouldMerge(shared_ptr<LogEvent>& lhs, shared_ptr<LogEvent>& rhs,
		const vector<int>& nonAdditiveFields) {
		const auto& l_values = lhs->getValues();
		const auto& r_values = rhs->getValues();

		for (size_t i : nonAdditiveFields) {
		// We store everything starting from index 0, so we need to use i-1
		if (!(l_values.size() > i - 1 && r_values.size() > i - 1 &&
		l_values[i - 1].mValue == r_values[i - 1].mValue)) {
		return false;
		}
		}
		return true;
		}

		// merge rhs to lhs
		// when calling this function, all sanity check should be done already.
		// e.g., index boundary, nonAdditiveFields matching etc.
		bool mergeEvent(shared_ptr<LogEvent>& lhs, shared_ptr<LogEvent>& rhs,
		const vector<int>& additiveFields) {
		vector<FieldValue>* host_values = lhs->getMutableValues();
		const auto& child_values = rhs->getValues();
		for (int i : additiveFields) {
		Value& host = (*host_values)[i - 1].mValue;
		const Value& child = (child_values[i - 1]).mValue;
		if (child.getType() != host.getType()) {
		return false;
		}
		switch (child.getType()) {
		case INT:
		host.setInt(host.int_value + child.int_value);
		break;
		case LONG:
		host.setLong(host.long_value + child.long_value);
		break;
		default:
		ALOGE("Tried to merge 2 fields with unsupported type");
		return false;
		}
		}
		return true;
		}

		bool tryMerge(vector<shared_ptr<LogEvent>>& data, int child_pos, const vector<int>& host_pos,
		const vector<int>& nonAdditiveFields, const vector<int>& additiveFields) {
		for (const auto& pos : host_pos) {
		if (shouldMerge(data[pos], data[child_pos], nonAdditiveFields) &&
		mergeEvent(data[pos], data[child_pos], additiveFields)) {
		return true;
		}
		}
		return false;
		}

		} // namespace

		/**
		* Process all data and merge isolated with host if necessary.
		* For example:
		@@ -41,7 +95,7 @@ using std::vector;
		* int byte_send = 3;
		* int byte_recv = 4;
		* }
		* additive fields are {3, 4}
		* additive fields are {3, 4}, non-additive field is {2}
		* If we pulled the following events (uid1_child is an isolated uid which maps to uid1):
		* [uid1, fg, 100, 200]
		* [uid1_child, fg, 100, 200]
		@@ -50,119 +104,65 @@ using std::vector;
		* We want to merge them and results should be:
		* [uid1, fg, 200, 400]
		* [uid1, bg, 100, 200]
		*
		* All atoms should be of the same tagId. All fields should be present.
		*/
		void mapAndMergeIsolatedUidsToHostUid(vector<shared_ptr<LogEvent>>& data, const sp<UidMap>& uidMap,
		void mergeIsolatedUidsToHostUid(vector<shared_ptr<LogEvent>>& data, const sp<UidMap>& uidMap,
		int tagId) {
		if (StatsPullerManager::kAllPullAtomInfo.find(tagId) ==
		StatsPullerManager::kAllPullAtomInfo.end()) {
		VLOG("Unknown pull atom id %d", tagId);
		return;
		}
		if ((android::util::AtomsInfo::kAtomsWithAttributionChain.find(tagId) ==
		android::util::AtomsInfo::kAtomsWithAttributionChain.end()) &&
		(android::util::AtomsInfo::kAtomsWithUidField.find(tagId) ==
		android::util::AtomsInfo::kAtomsWithUidField.end())) {
		VLOG("No uid or attribution chain to merge, atom %d", tagId);
		int uidField;
		auto it = android::util::AtomsInfo::kAtomsWithUidField.find(tagId);
		if (it == android::util::AtomsInfo::kAtomsWithUidField.end()) {
		VLOG("No uid to merge for atom %d", tagId);
		return;
		} else {
		uidField = it->second; // uidField is the field number in proto,
		}
		const vector<int>& additiveFields =
		StatsPullerManager::kAllPullAtomInfo.find(tagId)->second.additiveFields;
		const vector<int>& nonAdditiveFields =
		StatsPullerManager::kAllPullAtomInfo.find(tagId)->second.nonAdditiveFields;

		// 1. Map all isolated uid in-place to host uid
		for (shared_ptr<LogEvent>& event : data) {
		if (event->GetTagId() != tagId) {
		ALOGE("Wrong atom. Expecting %d, got %d", tagId, event->GetTagId());
		return;
		}
		if (android::util::AtomsInfo::kAtomsWithAttributionChain.find(tagId) !=
		android::util::AtomsInfo::kAtomsWithAttributionChain.end()) {
		for (auto& value : *(event->getMutableValues())) {
		if (value.mField.getPosAtDepth(0) > kAttributionField) {
		break;
		}
		if (isAttributionUidField(value)) {
		const int hostUid = uidMap->getHostUidOrSelf(value.mValue.int_value);
		value.mValue.setInt(hostUid);
		// map of host uid to their position in the original vector
		map<int, vector<int>> hostPosition;
		vector<bool> toRemove = vector<bool>(data.size(), false);

		for (size_t i = 0; i < data.size(); i++) {
		vector<FieldValue>* valueList = data[i]->getMutableValues();

		int uid;
		if (uidField > 0 && (int)data[i]->getValues().size() >= uidField &&
		(data[i]->getValues())[uidField - 1].mValue.getType() == INT) {
		uid = (*data[i]->getMutableValues())[uidField - 1].mValue.int_value;
		} else {
		ALOGE("Malformed log, uid not found. %s", data[i]->ToString().c_str());
		continue;
		}

		const int hostUid = uidMap->getHostUidOrSelf(uid);

		if (hostUid != uid) {
		(*valueList)[0].mValue.setInt(hostUid);
		}
		if (hostPosition.find(hostUid) == hostPosition.end()) {
		hostPosition[hostUid].push_back(i);
		} else {
		auto it = android::util::AtomsInfo::kAtomsWithUidField.find(tagId);
		if (it != android::util::AtomsInfo::kAtomsWithUidField.end()) {
		int uidField = it->second; // uidField is the field number in proto,
		// starting from 1
		if (uidField > 0 && (int)event->getValues().size() >= uidField &&
		(event->getValues())[uidField - 1].mValue.getType() == INT) {
		Value& value = (*event->getMutableValues())[uidField - 1].mValue;
		const int hostUid = uidMap->getHostUidOrSelf(value.int_value);
		value.setInt(hostUid);
		if (tryMerge(data, i, hostPosition[hostUid], nonAdditiveFields, additiveFields)) {
		toRemove[i] = true;
		} else {
		ALOGE("Malformed log, uid not found. %s", event->ToString().c_str());
		return;
		}
		hostPosition[hostUid].push_back(i);
		}
		}
		}

		// 2. sort the data, bit-wise
		sort(data.begin(), data.end(),
		[](const shared_ptr<LogEvent>& lhs, const shared_ptr<LogEvent>& rhs) {
		if (lhs->size() != rhs->size()) {
		return lhs->size() < rhs->size();
		}
		const std::vector<FieldValue>& lhsValues = lhs->getValues();
		const std::vector<FieldValue>& rhsValues = rhs->getValues();
		for (int i = 0; i < (int)lhs->size(); i++) {
		if (lhsValues[i] != rhsValues[i]) {
		return lhsValues[i] < rhsValues[i];
		}
		}
		return false;
		});

		vector<shared_ptr<LogEvent>> mergedData;
		const vector<int>& additiveFieldsVec =
		StatsPullerManager::kAllPullAtomInfo.find(tagId)->second.additiveFields;
		const set<int> additiveFields(additiveFieldsVec.begin(), additiveFieldsVec.end());
		bool needMerge = true;

		// 3. do the merge.
		// The loop invariant is this: for every event, check if it differs on
		// non-additive fields, or have different attribution chain length.
		// If so, no need to merge, add itself to the result.
		// Otherwise, merge the value onto the one immediately next to it.
		for (int i = 0; i < (int)data.size() - 1; i++) {
		// Size different, must be different chains.
		if (data[i]->size() != data[i + 1]->size()) {
		for (size_t i = 0; i < toRemove.size(); i++) {
		if (!toRemove[i]) {
		mergedData.push_back(data[i]);
		continue;
		}
		vector<FieldValue>* lhsValues = data[i]->getMutableValues();
		vector<FieldValue>* rhsValues = data[i + 1]->getMutableValues();
		needMerge = true;
		for (int p = 0; p < (int)lhsValues->size(); p++) {
		if ((lhsValues)[p] != (rhsValues)[p]) {
		int pos = (*lhsValues)[p].mField.getPosAtDepth(0);
		// Differ on non-additive field, abort.
		if (additiveFields.find(pos) == additiveFields.end()) {
		needMerge = false;
		break;
		}
		}
		}
		if (!needMerge) {
		mergedData.push_back(data[i]);
		continue;
		}
		// This should be infrequent operation.
		for (int p = 0; p < (int)lhsValues->size(); p++) {
		int pos = (*lhsValues)[p].mField.getPosAtDepth(0);
		if (additiveFields.find(pos) != additiveFields.end()) {
		(rhsValues)[p].mValue += (lhsValues)[p].mValue;
		}
		}
		}
		mergedData.push_back(data.back());

		data.clear();
		data = mergedData;
		}