Merge "logd: remove min heap in SerializedFlushToState" am: b92ac53aeb am:... (009660b5) · Commits · e / os / android_system_core

logd/SerializedFlushToState.cpp

+33 −29

Original line number	Diff line number	Diff line
		@@ -16,6 +16,8 @@

		#include "SerializedFlushToState.h"

		#include <limits>

		#include <android-base/logging.h>

		SerializedFlushToState::SerializedFlushToState(uint64_t start, LogMask log_mask)
		@@ -63,14 +65,13 @@ void SerializedFlushToState::CreateLogPosition(log_id_t log_id) {
		log_positions_[log_id].emplace(log_position);
		}

		void SerializedFlushToState::AddMinHeapEntry(log_id_t log_id) {
		void SerializedFlushToState::UpdateLogsNeeded(log_id_t log_id) {
		auto& buffer_it = log_positions_[log_id]->buffer_it;
		auto read_offset = log_positions_[log_id]->read_offset;

		// If there is another log to read in this buffer, add it to the min heap.
		// If there is another log to read in this buffer, let it be read.
		if (read_offset < buffer_it->write_offset()) {
		auto* entry = buffer_it->log_entry(read_offset);
		min_heap_.emplace(log_id, entry);
		logs_needed_from_next_position_[log_id] = false;
		} else if (read_offset == buffer_it->write_offset()) {
		// If there are no more logs to read in this buffer and it's the last buffer, then
		// set logs_needed_from_next_position_ to wait until more logs get logged.
		@@ -85,8 +86,7 @@ void SerializedFlushToState::AddMinHeapEntry(log_id_t log_id) {
		if (buffer_it->write_offset() == 0) {
		logs_needed_from_next_position_[log_id] = true;
		} else {
		auto* entry = buffer_it->log_entry(0);
		min_heap_.emplace(log_id, entry);
		logs_needed_from_next_position_[log_id] = false;
		}
		}
		} else {
		@@ -106,24 +106,41 @@ void SerializedFlushToState::CheckForNewLogs() {
		}
		CreateLogPosition(i);
		}
		logs_needed_from_next_position_[i] = false;
		// If it wasn't possible to insert, logs_needed_from_next_position will be set back to true.
		AddMinHeapEntry(i);
		UpdateLogsNeeded(i);
		}
		}

		MinHeapElement SerializedFlushToState::PopNextUnreadLog() {
		auto top = min_heap_.top();
		min_heap_.pop();
		bool SerializedFlushToState::HasUnreadLogs() {
		CheckForNewLogs();
		log_id_for_each(i) {
		if (log_positions_[i] && !logs_needed_from_next_position_[i]) {
		return true;
		}
		}
		return false;
		}

		auto* entry = top.entry;
		auto log_id = top.log_id;
		LogWithId SerializedFlushToState::PopNextUnreadLog() {
		uint64_t min_sequence = std::numeric_limits<uint64_t>::max();
		log_id_t log_id;
		const SerializedLogEntry* entry = nullptr;
		log_id_for_each(i) {
		if (!log_positions_[i] \|\| logs_needed_from_next_position_[i]) {
		continue;
		}
		if (log_positions_[i]->log_entry()->sequence() < min_sequence) {
		log_id = i;
		entry = log_positions_[i]->log_entry();
		min_sequence = entry->sequence();
		}
		}
		CHECK_NE(nullptr, entry);

		log_positions_[log_id]->read_offset += entry->total_len();

		logs_needed_from_next_position_[log_id] = true;

		return top;
		return {log_id, entry};
		}

		void SerializedFlushToState::Prune(log_id_t log_id,
		@@ -133,25 +150,12 @@ void SerializedFlushToState::Prune(log_id_t log_id,
		return;
		}

		// // Decrease the ref count since we're deleting our reference.
		// Decrease the ref count since we're deleting our reference.
		buffer_it->DecReaderRefCount();

		// Delete in the reference.
		log_positions_[log_id].reset();

		// Remove the MinHeapElement referencing log_id, if it exists, but retain the others.
		std::vector<MinHeapElement> old_elements;
		while (!min_heap_.empty()) {
		auto& element = min_heap_.top();
		if (element.log_id != log_id) {
		old_elements.emplace_back(element);
		}
		min_heap_.pop();
		}
		for (auto&& element : old_elements) {
		min_heap_.emplace(element);
		}

		// Finally set logs_needed_from_next_position_, so CheckForNewLogs() will re-create the
		// log_position_ object during the next read.
		logs_needed_from_next_position_[log_id] = true;

logd/SerializedFlushToState.h

+14 −26

Original line number	Diff line number	Diff line
		@@ -27,26 +27,19 @@
		struct LogPosition {
		std::list<SerializedLogChunk>::iterator buffer_it;
		int read_offset;

		const SerializedLogEntry* log_entry() const { return buffer_it->log_entry(read_offset); }
		};

		struct MinHeapElement {
		MinHeapElement(log_id_t log_id, const SerializedLogEntry* entry)
		: log_id(log_id), entry(entry) {}
		struct LogWithId {
		log_id_t log_id;
		const SerializedLogEntry* entry;
		// The change of comparison operators is intentional, std::priority_queue uses operator<() to
		// compare but creates a max heap. Since we want a min heap, we return the opposite result.
		bool operator<(const MinHeapElement& rhs) const {
		return entry->sequence() > rhs.entry->sequence();
		}
		};

		// This class tracks the specific point where a FlushTo client has read through the logs. It
		// directly references the std::list<> iterators from the parent SerializedLogBuffer and the offset
		// into each log chunk where it has last read. All interactions with this class, except for its
		// construction, must be done with SerializedLogBuffer::lock_ held. No log chunks that it
		// references may be pruned, which is handled by ensuring prune does not touch any log chunk with
		// highest sequence number greater or equal to start().
		// construction, must be done with SerializedLogBuffer::lock_ held.
		class SerializedFlushToState : public FlushToState {
		public:
		// Initializes this state object. For each log buffer set in log_mask, this sets
		@@ -61,31 +54,29 @@ class SerializedFlushToState : public FlushToState {
		if (logs_ == nullptr) logs_ = logs;
		}

		bool HasUnreadLogs() {
		CheckForNewLogs();
		return !min_heap_.empty();
		}
		// Updates the state of log_positions_ and logs_needed_from_next_position_ then returns true if
		// there are any unread logs, false otherwise.
		bool HasUnreadLogs();

		// Pops the next unread log from the min heap and sets logs_needed_from_next_position_ to
		// indicate that we're waiting for more logs from the associated log buffer.
		MinHeapElement PopNextUnreadLog();
		// Returns the next unread log and sets logs_needed_from_next_position_ to indicate that we're
		// waiting for more logs from the associated log buffer.
		LogWithId PopNextUnreadLog();

		// If the parent log buffer prunes logs, the reference that this class contains may become
		// invalid, so this must be called first to drop the reference to buffer_it, if any.
		void Prune(log_id_t log_id, const std::list<SerializedLogChunk>::iterator& buffer_it);

		private:
		// If there is a log in the serialized log buffer for `log_id` at the read_offset, add it to the
		// min heap for reading, otherwise set logs_needed_from_next_position_ to indicate that we're
		// waiting for the next log.
		void AddMinHeapEntry(log_id_t log_id);
		// Set logs_needed_from_next_position_[i] to indicate if log_positions_[i] points to an unread
		// log or to the point at which the next log will appear.
		void UpdateLogsNeeded(log_id_t log_id);

		// Create a LogPosition object for the given log_id by searching through the log chunks for the
		// first chunk and then first log entry within that chunk that is greater or equal to start().
		void CreateLogPosition(log_id_t log_id);

		// Checks to see if any log buffers set in logs_needed_from_next_position_ have new logs and
		// calls AddMinHeapEntry() if so.
		// calls UpdateLogsNeeded() if so.
		void CheckForNewLogs();

		std::list<SerializedLogChunk>* logs_ = nullptr;
		@@ -97,7 +88,4 @@ class SerializedFlushToState : public FlushToState {
		// next_log_position == logs_write_position_)`. These will be re-checked in each
		// loop in case new logs came in.
		std::bitset<LOG_ID_MAX> logs_needed_from_next_position_ = {};
		// A min heap that has up to one entry per log buffer, sorted by sequence number, of the next
		// element that this reader should read.
		std::priority_queue<MinHeapElement> min_heap_;
		};

logd/SerializedFlushToStateTest.cpp

+18 −1

Original line number	Diff line number	Diff line
		@@ -288,3 +288,20 @@ TEST_F(SerializedFlushToStateTest, no_dangling_references) {

		EXPECT_FALSE(state.HasUnreadLogs());
		}

		TEST(SerializedFlushToState, Prune) {
		auto chunk = SerializedLogChunk{kChunkSize};
		chunk.Log(1, log_time(), 0, 1, 1, "abc", 3);
		chunk.Log(2, log_time(), 0, 1, 1, "abc", 3);
		chunk.Log(3, log_time(), 0, 1, 1, "abc", 3);
		chunk.FinishWriting();

		std::list<SerializedLogChunk> log_chunks[LOG_ID_MAX];
		log_chunks[LOG_ID_MAIN].emplace_back(std::move(chunk));

		auto state = SerializedFlushToState{1, kLogMaskAll};
		state.InitializeLogs(log_chunks);
		ASSERT_TRUE(state.HasUnreadLogs());

		state.Prune(LOG_ID_MAIN, log_chunks[LOG_ID_MAIN].begin());
		}

logd/SerializedLogBuffer.cpp

+1 −1

Original line number	Diff line number	Diff line
		@@ -211,7 +211,7 @@ bool SerializedLogBuffer::FlushTo(
		state.InitializeLogs(logs_);

		while (state.HasUnreadLogs()) {
		MinHeapElement top = state.PopNextUnreadLog();
		LogWithId top = state.PopNextUnreadLog();
		auto* entry = top.entry;
		auto log_id = top.log_id;

logd/SerializedLogChunk.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -18,6 +18,8 @@

		#include <sys/types.h>

		#include <android-base/logging.h>

		#include "LogWriter.h"
		#include "SerializedData.h"
		#include "SerializedLogEntry.h"
		@@ -55,6 +57,7 @@ class SerializedLogChunk {
		}

		const SerializedLogEntry* log_entry(int offset) const {
		CHECK(writer_active_ \|\| reader_ref_count_ > 0);
		return reinterpret_cast<const SerializedLogEntry*>(data() + offset);
		}
		const uint8_t* data() const { return contents_.data(); }