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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* Implementation of an asynchronous lock-free logging system. */
+
+#ifndef mozilla_dom_AsyncLogger_h
+#define mozilla_dom_AsyncLogger_h
+
+#include <atomic>
+#include <thread>
+#include <cinttypes>
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/BaseProfilerMarkerTypes.h"
+#include "mozilla/MathAlgorithms.h"
+#include "mozilla/Sprintf.h"
+#include "mozilla/TimeStamp.h"
+#include "GeckoProfiler.h"
+#include "MPSCQueue.h"
+
+#if defined(_WIN32)
+# include <process.h>
+# define getpid() _getpid()
+#else
+# include <unistd.h>
+#endif
+
+namespace mozilla {
+
+// Allows writing 0-terminated C-strings in a buffer, and returns the start
+// index of the string that's been appended. Automatically truncates the strings
+// as needed if the storage is too small, returning true when that's the case.
+class MOZ_STACK_CLASS StringWriter {
+ public:
+ StringWriter(char* aMemory, size_t aLength)
+ : mMemory(aMemory), mWriteIndex(0), mLength(aLength) {}
+
+ bool AppendCString(const char* aString, size_t* aIndexStart) {
+ *aIndexStart = mWriteIndex;
+ if (!aString) {
+ return false;
+ }
+ size_t toCopy = strlen(aString);
+ bool truncated = false;
+
+ if (toCopy > Available()) {
+ truncated = true;
+ toCopy = Available() - 1;
+ }
+
+ memcpy(&(mMemory[mWriteIndex]), aString, toCopy);
+ mWriteIndex += toCopy;
+ mMemory[mWriteIndex] = 0;
+ mWriteIndex++;
+
+ return truncated;
+ }
+
+ private:
+ size_t Available() {
+ MOZ_ASSERT(mLength > mWriteIndex);
+ return mLength - mWriteIndex;
+ }
+
+ char* mMemory;
+ size_t mWriteIndex;
+ size_t mLength;
+};
+
+const size_t PAYLOAD_TOTAL_SIZE = 2 << 9;
+
+// This class implements a lock-free asynchronous logger, that
+// adds profiler markers.
+// Any thread can use this logger without external synchronization and without
+// being blocked. This log is suitable for use in real-time audio threads.
+// This class uses a thread internally, and must be started and stopped
+// manually.
+// If profiling is disabled, all the calls are no-op and cheap.
+class AsyncLogger {
+ public:
+ enum class TracingPhase : uint8_t { BEGIN, END, COMPLETE };
+
+ const char TRACING_PHASE_STRINGS[3] = {'B', 'E', 'X'};
+
+ struct TextPayload {
+ char mPayload[PAYLOAD_TOTAL_SIZE - MPSC_MSG_RESERVED];
+ };
+
+ // The order of the fields is important here to minimize padding.
+ struct TracePayload {
+#define MEMBERS_EXCEPT_NAME \
+ /* If this marker is of phase B or E (begin or end), this is the time at \
+ * which it was captured. */ \
+ TimeStamp mTimestamp; \
+ /* The thread on which this tracepoint was gathered. */ \
+ ProfilerThreadId mTID; \
+ /* If this marker is of phase X (COMPLETE), this holds the duration of the \
+ * event in microseconds. Else, the value is not used. */ \
+ uint32_t mDurationUs; \
+ /* A trace payload can be either: \
+ * - Begin - this marks the beginning of a temporal region \
+ * - End - this marks the end of a temporal region \
+ * - Complete - this is a timestamp and a length, forming complete a \
+ * temporal region */ \
+ TracingPhase mPhase; \
+ /* Offset at which the comment part of the string starts, in mName */ \
+ uint8_t mCommentStart;
+
+ MEMBERS_EXCEPT_NAME;
+
+ private:
+ // Mock structure, to know where the first character of the name will be.
+ struct MembersWithChar {
+ MEMBERS_EXCEPT_NAME;
+ char c;
+ };
+ static constexpr size_t scRemainingSpaceForName =
+ PAYLOAD_TOTAL_SIZE - offsetof(MembersWithChar, c) -
+ ((MPSC_MSG_RESERVED + alignof(MembersWithChar) - 1) &
+ ~(alignof(MembersWithChar) - 1));
+#undef MEMBERS_EXCEPT_NAME
+
+ public:
+ // An arbitrary string, usually containing a function signature or a
+ // recognizable tag of some sort, to be displayed when analyzing the
+ // profile.
+ char mName[scRemainingSpaceForName];
+ };
+
+ // The goal here is to make it easy on the allocator. We pack a pointer in the
+ // message struct, and we still want to do power of two allocations to
+ // minimize allocator slop.
+ static_assert(sizeof(MPSCQueue<TracePayload>::Message) == PAYLOAD_TOTAL_SIZE,
+ "MPSCQueue internal allocations has an unexpected size.");
+
+ explicit AsyncLogger() : mThread(nullptr), mRunning(false) {}
+
+ void Start() {
+ MOZ_ASSERT(!mRunning, "Double calls to AsyncLogger::Start");
+ mRunning = true;
+ Run();
+ }
+
+ void Stop() {
+ if (mRunning) {
+ mRunning = false;
+ }
+ }
+
+ // Log something that has a beginning and an end
+ void Log(const char* aName, const char* aCategory, const char* aComment,
+ TracingPhase aPhase) {
+ if (!Enabled()) {
+ return;
+ }
+
+ auto* msg = new MPSCQueue<TracePayload>::Message();
+
+ msg->data.mTID = profiler_current_thread_id();
+ msg->data.mPhase = aPhase;
+ msg->data.mTimestamp = TimeStamp::Now();
+ msg->data.mDurationUs = 0; // unused, duration is end - begin
+
+ StringWriter writer(msg->data.mName, ArrayLength(msg->data.mName));
+
+ size_t commentIndex;
+ DebugOnly<bool> truncated = writer.AppendCString(aName, &commentIndex);
+ MOZ_ASSERT(!truncated, "Tracing payload truncated: name");
+
+ if (aComment) {
+ truncated = writer.AppendCString(aComment, &commentIndex);
+ MOZ_ASSERT(!truncated, "Tracing payload truncated: comment");
+ msg->data.mCommentStart = commentIndex;
+ } else {
+ msg->data.mCommentStart = 0;
+ }
+ mMessageQueueProfiler.Push(msg);
+ }
+
+ // Log something that has a beginning and a duration
+ void LogDuration(const char* aName, const char* aCategory, uint64_t aDuration,
+ uint64_t aFrames, uint64_t aSampleRate) {
+ if (Enabled()) {
+ auto* msg = new MPSCQueue<TracePayload>::Message();
+ msg->data.mTID = profiler_current_thread_id();
+ msg->data.mPhase = TracingPhase::COMPLETE;
+ msg->data.mTimestamp = TimeStamp::Now();
+ msg->data.mDurationUs =
+ (static_cast<double>(aFrames) / aSampleRate) * 1e6;
+ size_t len = std::min(strlen(aName), ArrayLength(msg->data.mName));
+ memcpy(msg->data.mName, aName, len);
+ msg->data.mName[len] = 0;
+ mMessageQueueProfiler.Push(msg);
+ }
+ }
+
+ bool Enabled() { return mRunning; }
+
+ private:
+ void Run() {
+ mThread.reset(new std::thread([this]() {
+ AUTO_PROFILER_REGISTER_THREAD("AsyncLogger");
+ while (mRunning) {
+ {
+ struct TracingMarkerWithComment {
+ static constexpr Span<const char> MarkerTypeName() {
+ return MakeStringSpan("Real-Time");
+ }
+ static void StreamJSONMarkerData(
+ baseprofiler::SpliceableJSONWriter& aWriter,
+ const ProfilerString8View& aText) {
+ aWriter.StringProperty("name", aText);
+ }
+ static MarkerSchema MarkerTypeDisplay() {
+ using MS = MarkerSchema;
+ MS schema{MS::Location::MarkerChart, MS::Location::MarkerTable};
+ schema.SetChartLabel("{marker.data.name}");
+ schema.SetTableLabel("{marker.name} - {marker.data.name}");
+ schema.AddKeyLabelFormatSearchable("name", "Comment",
+ MS::Format::String,
+ MS::Searchable::Searchable);
+ return schema;
+ }
+ };
+
+ struct TracingMarker {
+ static constexpr Span<const char> MarkerTypeName() {
+ return MakeStringSpan("Real-time");
+ }
+ static void StreamJSONMarkerData(
+ baseprofiler::SpliceableJSONWriter& aWriter) {}
+ static MarkerSchema MarkerTypeDisplay() {
+ using MS = MarkerSchema;
+ MS schema{MS::Location::MarkerChart, MS::Location::MarkerTable};
+ // Nothing outside the defaults.
+ return schema;
+ }
+ };
+
+ TracePayload message;
+ while (mMessageQueueProfiler.Pop(&message) && mRunning) {
+ if (message.mPhase != TracingPhase::COMPLETE) {
+ if (!message.mCommentStart) {
+ profiler_add_marker(
+ ProfilerString8View::WrapNullTerminatedString(
+ message.mName),
+ geckoprofiler::category::MEDIA_RT,
+ {MarkerThreadId(message.mTID),
+ (message.mPhase == TracingPhase::BEGIN)
+ ? MarkerTiming::IntervalStart(message.mTimestamp)
+ : MarkerTiming::IntervalEnd(message.mTimestamp)},
+ TracingMarker{});
+ } else {
+ profiler_add_marker(
+ ProfilerString8View::WrapNullTerminatedString(
+ message.mName),
+ geckoprofiler::category::MEDIA_RT,
+ {MarkerThreadId(message.mTID),
+ (message.mPhase == TracingPhase::BEGIN)
+ ? MarkerTiming::IntervalStart(message.mTimestamp)
+ : MarkerTiming::IntervalEnd(message.mTimestamp)},
+ TracingMarkerWithComment{},
+ ProfilerString8View::WrapNullTerminatedString(
+ &(message.mName[message.mCommentStart])));
+ }
+ } else {
+ profiler_add_marker(
+ ProfilerString8View::WrapNullTerminatedString(message.mName),
+ geckoprofiler::category::MEDIA_RT,
+ {MarkerThreadId(message.mTID),
+ MarkerTiming::Interval(
+ message.mTimestamp,
+ message.mTimestamp + TimeDuration::FromMicroseconds(
+ message.mDurationUs))},
+ TracingMarker{});
+ }
+ }
+ }
+ Sleep();
+ }
+ }));
+ // cleanup is done via mRunning
+ mThread->detach();
+ }
+
+ uint64_t NowInUs() {
+ static TimeStamp base = TimeStamp::Now();
+ return (TimeStamp::Now() - base).ToMicroseconds();
+ }
+
+ void Sleep() { std::this_thread::sleep_for(std::chrono::milliseconds(10)); }
+
+ std::unique_ptr<std::thread> mThread;
+ MPSCQueue<TracePayload> mMessageQueueProfiler;
+ std::atomic<bool> mRunning;
+};
+
+} // end namespace mozilla
+
+#if defined(_WIN32)
+# undef getpid
+#endif
+
+#endif // mozilla_dom_AsyncLogger_h
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