perfetto: Add iorap.cmd.perfetto command line tool
Connect to libperfetto from iorap via an rx abstraction.
This standalone command line tool is used to validate integration
functionality.
Notes:
* Needs 'adb shell setenforce 0' to run, otherwise traced connection
will fail.
* Use 'trace_to_text systrace <filename.pb>' to dump the output proto in
a human-readable text form.
Test: adb shell iorap.cmd.perfetto -v --output-proto /data/local/tmp/trace.pb
Test: adb shell iorap.cmd.perfetto -v --output-proto /data/local/tmp/trace.pb --simple
Test: adb pull /data/local/tmp/trace.pb && trace_to_text systrace trace.pb
Bug: 72170747
Change-Id: I17a05d6da469bea7af36871a2e90c508f1549e15
diff --git a/src/perfetto/rx_producer.cc b/src/perfetto/rx_producer.cc
new file mode 100644
index 0000000..14311a1
--- /dev/null
+++ b/src/perfetto/rx_producer.cc
@@ -0,0 +1,865 @@
+// Copyright (C) 2019 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.
+
+#include "common/debug.h"
+#include "common/expected.h"
+#include "perfetto/rx_producer.h"
+
+#include <android-base/file.h>
+#include <android-base/properties.h>
+#include <android-base/unique_fd.h>
+
+#include <iostream>
+
+#include <sched.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <syscall.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+// TODO: move to perfetto code
+namespace perfetto {
+namespace consumer {
+
+std::ostream& operator<<(std::ostream& os, State state) {
+ switch (state) {
+ case State::kTraceFailed:
+ os << "kTraceFailed";
+ break;
+ case State::kConnectionError:
+ os << "kConnectionError";
+ break;
+ case State::kSessionNotFound:
+ os << "kSessionNotFound";
+ break;
+ case State::kIdle:
+ os << "kIdle";
+ break;
+ case State::kConnecting:
+ os << "kConnecting";
+ break;
+ case State::kConfigured:
+ os << "kConfigured";
+ break;
+ case State::kTracing:
+ os << "kTracing";
+ break;
+ case State::kTraceEnded:
+ os << "kTraceEnded";
+ break;
+ default:
+ os << "(unknown)"; // did someone forget to update this code?
+ break;
+ }
+ return os;
+}
+
+} // namespace consumer
+} // namespace perfetto
+
+namespace iorap::perfetto {
+
+PerfettoDependencies::Component PerfettoDependencies::CreateComponent() {
+ // TODO: read from config.
+ static const uint32_t kTraceDurationMs =
+ ::android::base::GetUintProperty("iorapd.perfetto.trace_duration_ms", /*default*/5000U);
+
+ static const uint32_t kBufferSize =
+ ::android::base::GetUintProperty("iorapd.perfetto.buffer_size", /*default*/4096U);
+
+ return fruit::createComponent()
+ .bind<PerfettoConsumer, PerfettoConsumerImpl>()
+ .registerProvider([]() /* -> TraceConfig */ {
+ return CreateConfig(kTraceDurationMs,
+ /*deferred_start*/true,
+ kBufferSize);
+ });
+}
+
+::perfetto::protos::TraceConfig PerfettoDependencies::CreateConfig(uint32_t duration_ms,
+ bool deferred_start,
+ uint32_t buffer_size) {
+ ::perfetto::protos::TraceConfig trace_config;
+
+ trace_config.set_duration_ms(duration_ms);
+ trace_config.add_buffers()->set_size_kb(buffer_size);
+ trace_config.set_deferred_start(deferred_start);
+
+ auto* ds_config = trace_config.add_data_sources()->mutable_config();
+ ds_config->set_name("linux.ftrace");
+ ds_config->mutable_ftrace_config()->add_ftrace_events(
+ "mm_filemap_add_to_page_cache");
+ ds_config->mutable_ftrace_config()->add_ftrace_events(
+ "mm_filemap_delete_from_page_cache");
+ ds_config->set_target_buffer(0);
+
+ return trace_config;
+}
+
+// RAII-style wrapper around a perfetto handle that calls Destroy
+// in a thread-safe manner.
+struct PerfettoConsumerHandle {
+ private:
+ std::shared_ptr<PerfettoConsumer> consumer_;
+ PerfettoConsumer::Handle handle_;
+
+ public:
+ // Takes over ownership of the 'handle'.
+ //
+ // Consumer must not be null.
+ PerfettoConsumerHandle(std::shared_ptr<PerfettoConsumer> consumer,
+ PerfettoConsumer::Handle handle)
+ : consumer_{std::move(consumer)},
+ handle_{std::move(handle)} {
+ DCHECK(consumer_ != nullptr);
+ }
+
+ std::shared_ptr<PerfettoConsumer> GetConsumer() const {
+ return consumer_;
+ }
+
+ PerfettoConsumer::Handle GetHandle() const {
+ return handle_;
+ }
+
+ ~PerfettoConsumerHandle() {
+ LOG(VERBOSE) << "PerfettoConsumerHandle::Destroy(" << handle_ << ")";
+ consumer_->Destroy(handle_);
+ }
+
+ bool operator==(const PerfettoConsumerHandle& other) const {
+ return handle_ == other.handle_ && consumer_ == other.consumer_;
+ }
+
+ bool operator!=(const PerfettoConsumerHandle& other) const {
+ return !(*this == other);
+ }
+};
+
+
+// Snapshot of a single perfetto OnStateChanged callback.
+//
+// Operate on the PerfettoConsumer to further change the state.
+//
+// The Handle is kept 'valid' until all references to the PerfettoConsumerHandle
+// are dropped to 0. This ensures the Handle is not destroyed too early. All
+// direct usages of 'Handle' must be scoped by the PerfettoConsumerHandle.
+struct PerfettoStateChange {
+ public:
+ using State = ::perfetto::consumer::State;
+ using Handle = ::perfetto::consumer::Handle;
+
+ State state; // Never invalid.
+ std::shared_ptr<PerfettoConsumerHandle> perfetto_consumer_and_handle; // Never null.
+
+ // Safety: Use only within scope of the PerfettoStateChange.
+ Handle GetHandle() const {
+ // TODO: it would be even safer to wrap all the calls to the handle inside a class,
+ // instead of exposing this raw Handle.
+ return perfetto_consumer_and_handle->GetHandle();
+ }
+
+ std::shared_ptr<PerfettoConsumer> GetConsumer() const {
+ return perfetto_consumer_and_handle->GetConsumer();
+ }
+};
+
+std::ostream& operator<<(std::ostream& os, const PerfettoStateChange& state_change) {
+ os << "PerfettoStateChange{" << state_change.state << ","
+ << state_change.GetHandle() << ","
+ << state_change.GetConsumer().get() << "}";
+ return os;
+}
+
+// Once created, this acts as a hot observable, emitting 'PerfettoStateChange' transition items.
+// Only the 'state' will vary, the handle and perfetto_consumer are always the same value.
+//
+// Clients only need to handle the success states in #on_next, all failure states will go to
+// #on_error.
+//
+// Upon reaching the appropriate terminal states, either #on_completed or #on_error is called.
+// No future callbacks will then occur, so this object should be subsequently deleted.
+//
+// The Handle is destroyed automatically after the last item is emitted, so it must only be
+// manipulated from the #on_next callbacks. Do not save the Handle and use it at other times.
+class StateChangedSubject {
+ public:
+ using State = ::perfetto::consumer::State;
+ using Handle = ::perfetto::consumer::Handle;
+
+ StateChangedSubject(const ::perfetto::protos::TraceConfig& trace_config,
+ rxcpp::subscriber<PerfettoStateChange> destination,
+ std::shared_ptr<PerfettoConsumer> perfetto_consumer)
+ : deferred_start(trace_config.deferred_start()),
+ dest(std::move(destination)),
+ perfetto_consumer_(std::move(perfetto_consumer)) {
+ DCHECK(perfetto_consumer_ != nullptr);
+ }
+
+ private:
+ struct StateChangedError : public std::runtime_error {
+ explicit StateChangedError(const std::string& what_arg) : std::runtime_error(what_arg) {}
+ };
+
+ std::shared_ptr<PerfettoConsumerHandle> handle_; // non-null after bound_ == true.
+ std::atomic<bool> bound_{false}; // synchronize-with for BindHandle -> OnStateChanged.
+
+ State last_state{State::kIdle};
+ bool deferred_start{false};
+
+ rxcpp::subscriber<PerfettoStateChange> dest;
+ std::shared_ptr<PerfettoConsumer> perfetto_consumer_; // This is never null.
+
+ void DcheckBadStateTransition(State state, bool fail_unless = false) const {
+ DCHECK(fail_unless) << "Invalid state transition to " << state << " from " << last_state;
+ }
+
+ void DcheckValidStateTransition(State state) {
+ // State must not be out of range.
+ DCHECK_GE(state, State::kTraceFailed);
+ DCHECK_LE(state, State::kTraceEnded);
+
+ // Internal state that should never leak out into public perfetto API:
+ DCHECK_NE(state, State::kIdle);
+ // These can only be returned by PollState:
+ DCHECK_NE(state, State::kSessionNotFound);
+
+ // Validate state transitions as per the perfetto API contract.
+ // See the 'state diagram' in consumer_api.h
+ switch (last_state) {
+ case State::kTraceFailed: // Final and unrecoverable.
+ // b/122548195: this can transition to 'kConnectionError' if selinux is disabled.
+ if (state == State::kConnectionError) {
+ LOG(WARNING) << "b/122548195: kTraceFailed is non-terminal, ignoring.";
+ // This is a bit awkward: rxcpp will drop the #on_error calls if its more than once.
+ break;
+ }
+ DcheckBadStateTransition(state);
+ break;
+ case State::kConnectionError: // Final and unrecoverable.
+ DcheckBadStateTransition(state);
+ break;
+ case State::kSessionNotFound:
+ DcheckBadStateTransition(state);
+ break;
+ case State::kIdle:
+ // OK: we initialized our own state to idle prior to the first callback.
+ break;
+ case State::kConnecting:
+ switch (state) {
+ case State::kConfigured:
+ // kConfigured, if |deferred_start| == true in the trace config.
+ DcheckBadStateTransition(state, deferred_start);
+ break;
+ case State::kTracing:
+ // kTracing, if |deferred_start| == false.
+ DcheckBadStateTransition(state, !deferred_start);
+ break;
+ case State::kConnectionError:
+ // An error state, e.g. if cannot reach the traced daemon.
+ break;
+ default:
+ // Unconditionally invalid state transitions from kConnecting to anything else.
+ DcheckBadStateTransition(state);
+ }
+ break;
+ case State::kConfigured:
+ DCHECK(deferred_start);
+ if (state != State::kTracing // OK: this is documented.
+ && state != State::kTraceFailed) { // Undocumented selinux failure.
+ // Undocumented, but it appears to go directly from Configured->TraceEnded
+ // it can also go to kTraceFailed if e.g. there's an selinux violation
+ // however this appears to be underdocumented.
+ // b/122607276 #2
+
+ if (state != State::kTraceEnded) { // b/122607276 #1
+ DcheckBadStateTransition(state);
+ }
+ }
+ break;
+ case State::kTracing:
+ switch (state) {
+ case State::kTraceEnded:
+ break;
+ case State::kTraceFailed:
+ break;
+ default:
+ DcheckBadStateTransition(state);
+ }
+ break;
+ case State::kTraceEnded:
+ // Cannot transition from terminal state to another state.
+ DcheckBadStateTransition(state);
+ break;
+
+ // default: This list is exhaustive
+ }
+ }
+
+ constexpr bool IsTerminalState() const {
+ switch (last_state) {
+ case State::kTraceFailed:
+ case State::kConnectionError:
+ case State::kTraceEnded:
+ return true;
+ default:
+ return false;
+ }
+ }
+
+ // Returns true for non-terminal states (i.e. this callback will be invoked again).
+ // Returns false otherwise.
+ bool OnStateChanged(Handle handle, State state) {
+ using namespace ::perfetto::consumer;
+
+ // Block until 'BoundHandle' is called by the other thread.
+ while (!bound_.load()) {} // seq_cst acquire.
+
+ std::shared_ptr<PerfettoConsumerHandle> handle_ptr = handle_;
+ DCHECK(handle_ptr != nullptr);
+
+ DCHECK_EQ(handle_ptr->GetHandle(), handle);
+ DcheckValidStateTransition(state);
+
+ switch (state) {
+ // Error states (terminal).
+ case State::kTraceFailed:
+ EmitError("kTraceFailed");
+ break;
+ case State::kConnectionError:
+ EmitError("kConnectionError");
+ break;
+
+ // Regular transitions (non-terminal).
+ case State::kConnecting:
+ case State::kConfigured:
+ case State::kTracing:
+ EmitNext(state);
+ break;
+ // Regular transitions (terminal).
+ case State::kTraceEnded: // XX: do we even need to emit the 'TraceEnded' state?
+ EmitNext(state);
+ dest.on_completed();
+ break;
+ default:
+ DcheckBadStateTransition(state);
+ }
+
+ bool force_non_terminal = false;
+
+ if (last_state == State::kConfigured && state == State::kConnectionError) {
+ // b/122548195: this can transition to 'kConnectionError' if selinux is disabled.
+ force_non_terminal = true;
+ // This function must 'return true' in this buggy case, otherwise we will
+ // call the destructor too early and subsequent callbacks will crash.
+ }
+
+ // Remember the state to validate prior state transitions.
+ last_state = state;
+
+ // The owner of this class should avoid leaking memory once we reach a terminal state.
+ return !IsTerminalState() || force_non_terminal;
+ }
+
+ public:
+ // Thread safety: Called by main thread, terminates the rx stream.
+ // When this function is invoked, no calls to this class from other threads can occur.
+ void OnCreateFailed() {
+ // returned when an invalid handle is passed to PollState().
+ last_state = State::kSessionNotFound;
+ EmitError("Create returned kInvalidHandle");
+ }
+
+ // Thread safety: Called by main thread, this could be concurrent to
+ // 'CallbackOnStateChanged'.
+ void BindHandle(const std::shared_ptr<PerfettoConsumerHandle>& handle) {
+ handle_ = handle;
+
+ // Unblock OnStateChanged.
+ bound_.store(true); // seq_cst release.
+ }
+
+ // Thread safety: Called by libperfetto background thread (same one every time).
+ static void CallbackOnStateChanged(Handle handle, State state, void* callback_arg) {
+ LOG(VERBOSE) << "CallbackOnStateChanged(handle=" << handle << ",state=" << state
+ << ",callback_arg=" << callback_arg << ")";
+
+ // Validate OnStateChanged callback invariants, guaranteed by libperfetto.
+ DCHECK_NE(handle, ::perfetto::consumer::kInvalidHandle);
+
+ // Note: Perfetto guarantees this callback always occurs on the same thread,
+ // so we don't need to do any extra thread synchronization here since we are only mutating
+ // StateChangedSubject from within this function.
+
+ // TODO: the memory ordering guarantees should be explicitly specified in consumer_api.h:
+ // This isn't specific enough:
+ // "The callback will be invoked on an internal thread and must not block."
+ // However looking at the implementation it posts onto a single-thread task runner,
+ // so this must be the case.
+
+ StateChangedSubject* state_subject = reinterpret_cast<StateChangedSubject*>(callback_arg);
+ // This current thread owns 'StateChangedSubject', no other threads must access it.
+ // Explicit synchronization is not necessary.
+
+ if (!state_subject->OnStateChanged(handle, state)) {
+ // Clean up the state tracker when we reach a terminal state.
+ // This means that no future callbacks will occur anymore.
+ delete state_subject;
+ }
+ }
+
+ private:
+ void EmitError(const std::string& msg) {
+ // Sidenote: Exact error class does not matter, rxcpp only lets us access the error
+ // as a string (rxcpp::util::what).
+ //
+ // Either way, the recovery strategy is identical (log then try and restart).
+ dest.on_error(rxcpp::util::make_error_ptr(StateChangedError{msg}));
+ }
+
+ void EmitNext(State state) {
+ if (WOULD_LOG(VERBOSE) && !dest.is_subscribed()) {
+ // This is purely for logging: #on_next already filters out items after unsubscription.
+ LOG(VERBOSE) << "StateChangedSubject#EmitNext(" << state << ") - drop due to unsubscribe";
+ }
+
+ auto handle_ptr = handle_;
+ DCHECK(handle_ptr != nullptr);
+
+ // Non-null guarantee for the items emitted into this stream.
+ PerfettoStateChange state_change{state, handle_ptr};
+ dest.on_next(std::move(state_change));
+ }
+
+ // TODO: inherit from rx subject and handle #unsubscribe explicitly, instead
+ // of just being subject-like?
+};
+
+// Note: The states will be emitted on a separate thread, so e.g. #as_blocking()
+// needs to be used to avoid dropping everything on the floor.
+//
+// Important: The #on_error case must be handled explicitly by the observable,
+// because the default behavior is to 'throw' which will cause an std::terminate with -fno-except.
+static auto /*[observable<State>, shared_ptr<PerfettoConsumerHandle>]*/
+ CreatePerfettoStateStream(::perfetto::protos::TraceConfig perfetto_config,
+ std::shared_ptr<PerfettoConsumer> perfetto_consumer) {
+ auto obs = rxcpp::observable<>::create<PerfettoStateChange>(
+ [perfetto_config = std::move(perfetto_config), perfetto_consumer = std::move(perfetto_consumer)]
+ (rxcpp::subscriber<PerfettoStateChange> subscriber) {
+ std::unique_ptr<StateChangedSubject> state_subject{
+ new StateChangedSubject{perfetto_config, subscriber, perfetto_consumer}};
+
+ // Perfetto API requires a pointer to a serialized protobuf, it doesn't accept
+ // the code-generated object.
+ std::string perfetto_config_str = perfetto_config.SerializeAsString();
+
+ ::perfetto::consumer::Handle handle =
+ perfetto_consumer->Create(perfetto_config_str.data(),
+ perfetto_config_str.size(),
+ // executes on the same background thread repeatedly.
+ &StateChangedSubject::CallbackOnStateChanged,
+ // inter-thread-move
+ reinterpret_cast<void*>(state_subject.get()));
+ // perfetto::consumer::Create synchronizes-with OnStateChanged callback, this means
+ // we don't need to explicitly synchronize state_subject here so long as we don't access
+ // it on this thread again.
+ LOG(DEBUG) << "Create Perfetto handle " << handle;
+
+ if (handle == ::perfetto::consumer::kInvalidHandle) {
+ LOG(ERROR) << "Failed to create Perfetto handle";
+ // No callbacks will occur, so our thread still owns the state subject.
+ state_subject->OnCreateFailed();
+ return;
+ }
+
+ std::shared_ptr<PerfettoConsumerHandle> safe_handle{
+ new PerfettoConsumerHandle{perfetto_consumer, handle}};
+
+ // Share ownership of the Handle with the StateSubject.
+ // This way we defer calling 'Destroy' until the callback reaches a terminal state
+ // *and* all users of the stream are done with the handle.
+ state_subject->BindHandle(safe_handle);
+
+ // state_subject ownership is taken over by OnStateChanged.
+ // It will also be touched in a separate thread, so we must never access it here again.
+ state_subject.release();
+
+ // 'subscriber#add' is actually a call to register an on_unsubscribe listener.
+ subscriber.add([safe_handle]() {
+ LOG(VERBOSE) << "PerfettoStateChange#unsubscribe";
+
+ // Release our ref-count to the handle.
+ // safe_handle.reset(); // This happens implicitly.
+
+ // TODO: I think this won't handle the case where we need to shut down early.
+ // Need to use the explicit kShutdown for that?
+ });
+
+ // TODO: this would be an excellent place to shuffle the perfetto config protobuf
+ // into a global debug state for dumpsys.
+ });
+
+ return obs;
+}
+
+template <typename T>
+bool BinaryWireProtobuf<T>::WriteFullyToFile(const std::string& path,
+ bool follow_symlinks) const {
+ // TODO: it would be great if android::base had a string_view overload to avoid copying
+ // data into an std::string.
+
+ // u g o
+ // rw-rw----
+ //
+ // Protobufs can be read/written but not executed.
+ static constexpr const mode_t kMode = S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP;
+
+ int flags =
+ O_WRONLY | O_CREAT | O_TRUNC | O_CLOEXEC | O_BINARY | (follow_symlinks ? 0 : O_NOFOLLOW);
+ android::base::unique_fd fd(TEMP_FAILURE_RETRY(open(path.c_str(), flags, kMode)));
+
+ if (fd == -1) {
+ PLOG(ERROR) << "BinaryWireProtobuf::WriteFullyToFile open failed";
+ return false;
+ }
+
+ if (!::android::base::WriteFully(fd, data_.data(), size())) {
+ PLOG(ERROR) << "BinaryWireProtobuf::WriteFullyToFile write failed";
+ return CleanUpAfterFailedWrite(path);
+ }
+
+ return true;
+}
+
+template <typename T>
+bool BinaryWireProtobuf<T>::CleanUpAfterFailedWrite(const std::string& path) {
+ // Something went wrong. Let's not leave a corrupt file lying around.
+ int saved_errno = errno;
+ unlink(path.c_str());
+ errno = saved_errno;
+ return false;
+}
+
+template <typename T>
+bool BinaryWireProtobuf<T>::WriteStringToFd(int fd) const {
+ const char* p = reinterpret_cast<const char*>(data_.data());
+ size_t left = size();
+ while (left > 0) {
+ ssize_t n = TEMP_FAILURE_RETRY(write(fd, p, left));
+ if (n == -1) {
+ return false;
+ }
+ p += n;
+ left -= n;
+ }
+ return true;
+}
+
+// explicit template instantiation.
+template struct BinaryWireProtobuf<::google::protobuf::MessageLite>;
+// TODO: refactor this not to need the template instantiation.
+
+#if defined(__ANDROID__)
+// Copy of the 2.6.18 kernel header (linux/ioprio.h)
+
+#define IOPRIO_WHO_PROCESS (1)
+#define IOPRIO_CLASS_IDLE (3)
+
+#define IOPRIO_BITS (16)
+#define IOPRIO_CLASS_SHIFT (13)
+#define IOPRIO_PRIO_MASK ((1UL << IOPRIO_CLASS_SHIFT) - 1)
+
+#define IOPRIO_PRIO_CLASS(mask) ((mask) >> IOPRIO_CLASS_SHIFT)
+#define IOPRIO_PRIO_DATA(mask) ((mask) & IOPRIO_PRIO_MASK)
+#define IOPRIO_PRIO_VALUE(class, data) (((class) << IOPRIO_CLASS_SHIFT) | data)
+#endif
+
+static int ioprio_get(int which, int who) {
+ return syscall(SYS_ioprio_get, which, who);
+}
+
+static int ioprio_set(int which, int who, int ioprio) {
+ return syscall(SYS_ioprio_set, which, who, ioprio);
+}
+
+// An rx Coordination, which will cause a new thread to spawn for each new Worker.
+//
+// Idle-class priority is set for the CPU and IO priorities on the new thread.
+rxcpp::observe_on_one_worker ObserveOnNewIoThread() {
+ // IO thread factory for idle-priority threads.
+ // Both the CPU scheduler and the IO scheduler are set to idle.
+ //
+ // Use this when needing to schedule disk access from a normal-priority thread onto a
+ // very low priority thread, but not so low that we need to use a BackgroundJobScheduler.
+ struct io_thread_factory {
+ std::thread operator()(std::function<void()> start) const {
+ return std::thread{
+ [start=std::move(start)]() {
+ // Set IO priority to idle.
+ do {
+ int value = ioprio_get(IOPRIO_WHO_PROCESS, /*pid*/0);
+ if (value == -1) {
+ PLOG(ERROR) << "io_thread_factory failed ioprio_get";
+ break; // Can't set the ioprio, we don't know what data to use.
+ }
+
+ int data = IOPRIO_PRIO_DATA(value); // priority level
+ // This appears to be '4' in practice. We may want to raise to
+ // be the highest-priority within the idle class.
+
+ // idle scheduling class. only access disk when nobody else needs disk.
+ int res = ioprio_set(IOPRIO_WHO_PROCESS,
+ /*pid*/0,
+ IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, data));
+ if (res < 0) {
+ PLOG(ERROR) << "io_thread_factory failed ioprio_set";
+ break;
+ }
+
+ // Changing the IO priority only has any effect with cfq scheduler:
+ // $> cat /sys/block/sda/queue/scheduler
+ LOG(VERBOSE) << "ioprio_set(WHO_PROCESS, class=IDLE, data=" << data << ")";
+ } while (false);
+
+ // Set CPU priority to idle.
+ do {
+ struct sched_param param{};
+ param.sched_priority = 0; // Required to be statically 0 when used with SCHED_IDLE.
+
+ if (sched_setscheduler(/*pid*/0, // current thread,
+ SCHED_IDLE,
+ /*in*/¶m) != 0) {
+ PLOG(ERROR) << "io_thread_factory failed sched_setscheduler";
+ break;
+ }
+
+ LOG(VERBOSE) << "sched_setscheduler(self, IDLE)";
+ } while (false);
+
+ // XX: if changing the scheduling is too aggressive (i.e. it causes starvation),
+ // we may want to stick with the default class and change the nice (priority) levels
+ // to the minimum.
+
+ // TODO: future work, maybe use cgroups configuration file instead?
+
+ // Call the rxcpp-supplied code.
+ start();
+ }
+ };
+ }
+ };
+
+ static rxcpp::schedulers::scheduler thread_scheduler =
+ rxcpp::schedulers::make_new_thread(io_thread_factory{});
+
+ static rxcpp::observe_on_one_worker observe_on_io_thread{thread_scheduler};
+
+ return observe_on_io_thread;
+}
+
+static auto/*observable<PerfettoTraceProto>*/
+ CreatePerfettoStream(rxcpp::observable<PerfettoStreamCommand> input,
+ std::shared_ptr<PerfettoConsumer> perfetto_consumer,
+ const ::perfetto::protos::TraceConfig& trace_config) {
+ // XX: should I also take a scheduler for input here???
+
+ auto /*observable<PerfettoStateChange>*/ perfetto_states =
+ CreatePerfettoStateStream(trace_config, perfetto_consumer);
+
+ using State = ::perfetto::consumer::State;
+
+ auto/*coordinator*/ serialize_coordinator = rxcpp::observe_on_new_thread();
+ // Rx note:
+ // The optimal thing to do would be to have a lock/unlock for an entire subset of a chain.
+ // This would avoid creating new threads, and could also be used to intentionally block
+ // the regular C-callback perfetto thread.
+ //
+ // It seems possible to create a coordinator to lock a single operator in a chain, but this
+ // appears to be unsound. In particular, it doesn't even make life any simpler below because
+ // it would only apply the synchronization to 'zip' but not 'flat_map' which is unsound.
+ //
+ // There is also the built-in 'serialize_new_thread' which seems to create a new thread but
+ // then never actually uses it, that seems unfortunate and wasteful.
+ //
+ // Instead, do the simple thing which is create a new thread and always queue on there.
+ // Execution an action on that worker is itself unsynchronized, but this doesn't matter since
+ // the worker is only backed by 1 thread (no 2 schedulables can be executed concurrently
+ // on the 'observe_new_thread' worker).
+ return input
+ .tap([](PerfettoStreamCommand command) {
+ LOG(VERBOSE) << "CreatePerfettoStreamCommand#tap(command=" << command << ")";
+ })
+ // Input A, thread tA. Input B, thread tB. Continue execution with (A,B) on thread tC.
+ .zip(serialize_coordinator, // rest of chain is also executed on the same thread.
+ perfetto_states)
+ // Note: zip terminates when either of the streams complete.
+ .flat_map(
+ [](std::tuple<PerfettoStreamCommand, PerfettoStateChange> p) {
+ auto& [command, state_change] = p;
+ LOG(VERBOSE) << "CreatePerfettoStream#combine("
+ << command << "," << state_change << ")";
+ if (command == PerfettoStreamCommand::kShutdown) {
+ // Perfetto: Always safe to call ::perfetto::consumer::Destroy
+ // at any time.
+ //
+ // XX: How do we clean up the StateChangedSubject without racing
+ // against the callback? It strikes me that we may need a 'kDestroyed'
+ // state that perfetto can transition to from kConfigured.
+ LOG(VERBOSE) << "Call Perfetto_Consumer->Destroy";
+ state_change.GetConsumer()->Destroy(state_change.GetHandle());
+
+ // XX: Do we even have any guarantees about not getting more callbacks?
+ // We could just say 'there can still be spurious output after Shutdown'
+ // and just ignore it (e.g. Shutdown and immediately unsubscribe).
+ } else if (command == PerfettoStreamCommand::kStartTracing
+ && state_change.state == State::kConfigured) {
+ LOG(VERBOSE) << "Call Perfetto_Consumer->StartTracing";
+ state_change.GetConsumer()->StartTracing(state_change.GetHandle());
+ } else if (command == PerfettoStreamCommand::kStopTracing &&
+ state_change.state == State::kTraceEnded) {
+ // TODO: if perfetto actually had a 'StopTracing' we could call that here.
+ // right now we just pretend it exists, but rely on the config timer instead.
+ ::perfetto::consumer::TraceBuffer trace_buffer =
+ state_change.GetConsumer()->ReadTrace(state_change.GetHandle());
+
+ LOG(VERBOSE) << "Perfetto Trace ended"
+ << ", addr=" << reinterpret_cast<void*>(trace_buffer.begin)
+ << ",size= " << trace_buffer.size;
+
+ PerfettoTraceProto wire_proto{trace_buffer.begin, trace_buffer.size};
+ return rxcpp::observable<>::just(std::move(wire_proto)).as_dynamic();
+ }
+ return rxcpp::observable<>::empty<PerfettoTraceProto>().as_dynamic();
+ }
+ );
+}
+
+std::ostream& operator<<(std::ostream& os, PerfettoStreamCommand c) {
+ switch (c) {
+ case PerfettoStreamCommand::kStartTracing:
+ os << "kStartTracing";
+ break;
+ case PerfettoStreamCommand::kStopTracing:
+ os << "kStopTracing";
+ break;
+ case PerfettoStreamCommand::kShutdown:
+ os << "kShutdown";
+ break;
+ default:
+ os << "(unknown)";
+ break;
+ }
+ return os;
+}
+
+RxProducerFactory::RxProducerFactory(PerfettoDependencies::Injector& injector)
+ : injector_(injector) {
+}
+
+// TODO: (fruit) maybe this could be streamlined further by avoiding this boilerplate?
+rxcpp::observable<PerfettoTraceProto> RxProducerFactory::CreateTraceStream(
+ rxcpp::observable<PerfettoStreamCommand> commands) {
+ std::shared_ptr<PerfettoConsumer> perfetto_consumer =
+ injector_.get<std::shared_ptr<PerfettoConsumer>>();
+ const ::perfetto::protos::TraceConfig& trace_config =
+ injector_.get<::perfetto::protos::TraceConfig>();
+
+ DCHECK(perfetto_consumer != nullptr);
+ DCHECK(reinterpret_cast<volatile const void*>(&trace_config) != nullptr);
+
+ return CreatePerfettoStream(commands,
+ perfetto_consumer,
+ trace_config);
+}
+
+// For testing/debugging only.
+//
+// Saves protobuf results in file name specified by 'arg_output_proto'.
+void CollectPerfettoTraceBufferImmediately(
+ RxProducerFactory& producer_factory,
+ const std::string& arg_output_proto) {
+ LOG(VERBOSE) << "CollectPerfettoTraceBufferImmediately";
+
+ std::shared_ptr<PerfettoConsumer> perfetto_consumer =
+ producer_factory.injector_.get<std::shared_ptr<PerfettoConsumer>>();
+ const ::perfetto::protos::TraceConfig& trace_config =
+ producer_factory.injector_.get<const ::perfetto::protos::TraceConfig&>();
+
+ auto /*observable<PerfettoStateChange>*/ perfetto_states =
+ CreatePerfettoStateStream(trace_config, perfetto_consumer);
+
+ perfetto_states
+ .as_blocking() // Wait for observable to terminate with on_completed or on_error.
+ .subscribe(/*on_next*/[&](auto state_change) {
+ LOG(VERBOSE) << "Perfetto post-processed State change: " << state_change;
+
+ using State = ::perfetto::consumer::State;
+ switch (state_change.state) {
+ case State::kConnecting:
+ LOG(VERBOSE) << "Perfetto Tracing is Connecting";
+ // Transitional state. No-op.
+ break;
+ case State::kConfigured:
+ state_change.GetConsumer()->StartTracing(state_change.GetHandle());
+ break;
+ case State::kTracing:
+ LOG(VERBOSE) << "Perfetto Tracing started";
+ // Transitional state. No-op.
+ break;
+ case State::kTraceEnded: {
+ ::perfetto::consumer::TraceBuffer trace_buffer =
+ state_change.GetConsumer()->ReadTrace(state_change.GetHandle());
+
+ LOG(VERBOSE) << "Perfetto Trace ended"
+ << ", addr=" << reinterpret_cast<void*>(trace_buffer.begin)
+ << ",size= " << trace_buffer.size;
+
+ if (!arg_output_proto.empty()) {
+ std::string trace_buffer_str;
+ trace_buffer_str.resize(trace_buffer.size);
+ std::copy(trace_buffer.begin,
+ trace_buffer.begin + trace_buffer.size,
+ trace_buffer_str.data());
+ if (!android::base::WriteStringToFile(trace_buffer_str, arg_output_proto)) {
+ LOG(ERROR) << "Failed to save TraceBuffer to " << arg_output_proto;
+ } else {
+ LOG(INFO) << "TraceBuffer saved to file: " << arg_output_proto;
+ LOG(INFO);
+ LOG(INFO) << "To print this in a human readable form, execute these commands:";
+ LOG(INFO) << "$> adb pull '" << arg_output_proto << "'";
+ LOG(INFO) << "$> trace_to_text systrace <filename.pb>";
+ }
+ }
+
+ // TODO: something more useful with this TraceBuffer, such as saving it to a file
+ // and printing the output.
+ break;
+ }
+ default:
+ // No other states are possible, because they go to #on_error or cause a dcheck.
+ DCHECK(false) << "Invalid state: " << state_change;
+ }
+
+ //INTENTIONAL_COMPILER_ERROR_HERE // lets make sure this code actually does a trace.
+
+ }, /*on_error*/[](rxcpp::util::error_ptr err) {
+ LOG(ERROR) << "Perfetto post-processed state change failed: " << rxcpp::util::what(err);
+ }, /*on_completed*/[]() {
+ LOG(VERBOSE) << "Perfetto post-processed State #on_completed";
+ });
+}
+
+
+} // namespace iorap::perfetto