src/bringup/bin/trace-benchmark/handler.h

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef ZIRCON_SYSTEM_UAPP_TRACE_BENCHMARK_HANDLER_H_
#define ZIRCON_SYSTEM_UAPP_TRACE_BENCHMARK_HANDLER_H_

#include <lib/async-loop/cpp/loop.h>
#include <lib/async-loop/default.h>
#include <lib/trace-provider/handler.h>
#include <lib/zx/event.h>
#include <stdio.h>
#include <zircon/assert.h>
#include <zircon/status.h>

#include <fbl/array.h>

class BenchmarkHandler : public trace::TraceHandler {
 public:
  static constexpr int kWaitStoppedTimeoutSeconds = 10;

  BenchmarkHandler(async::Loop* loop, trace_buffering_mode_t mode, size_t buffer_size)
      : loop_(loop), mode_(mode), buffer_(new uint8_t[buffer_size], buffer_size) {
    auto status = zx::event::create(0u, &observer_event_);
    ZX_DEBUG_ASSERT_MSG(status == ZX_OK, "zx::event::create returned %s\n",
                        zx_status_get_string(status));
    status = trace_register_observer(observer_event_.get());
    ZX_DEBUG_ASSERT_MSG(status == ZX_OK, "trace_register_observer returned %s\n",
                        zx_status_get_string(status));
  }

  ~BenchmarkHandler() {
    auto status = trace_unregister_observer(observer_event_.get());
    ZX_DEBUG_ASSERT_MSG(status == ZX_OK, "trace_unregister_observer returned %s\n",
                        zx_status_get_string(status));
  }

  trace_buffering_mode_t mode() const { return mode_; }

  void Start() {
    zx_status_t status =
        trace_engine_initialize(loop_->dispatcher(), this, mode_, buffer_.data(), buffer_.size());
    ZX_DEBUG_ASSERT_MSG(status == ZX_OK, "trace_engine_initialize returned %s\n",
                        zx_status_get_string(status));
    status = trace_engine_start(TRACE_START_CLEAR_ENTIRE_BUFFER);
    ZX_DEBUG_ASSERT_MSG(status == ZX_OK, "trace_engine_start returned %s\n",
                        zx_status_get_string(status));
    ZX_DEBUG_ASSERT(trace_state() == TRACE_STARTED);
    observer_event_.signal(ZX_EVENT_SIGNALED, 0u);
    trace_notify_observer_updated(observer_event_.get());
  }

  void Stop() {
    // Acquire the context before we stop. We can't after we stop
    // as the context has likely been released (no more
    // references).
    trace::internal::trace_buffer_header header;
    {
      auto context = trace::TraceProlongedContext::Acquire();
      trace_engine_terminate();
      trace_context_snapshot_buffer_header_internal(context.get(), &header);
    }

    // Tracing hasn't actually stopped yet. It's stopping, but that won't
    // complete until all context references are gone (which they are),
    // and the engine has processed that fact (which it hasn't necessarily
    // yet).
    while (trace_state() != TRACE_STOPPED) {
      auto status = observer_event_.wait_one(
          ZX_EVENT_SIGNALED, zx::deadline_after(zx::sec(kWaitStoppedTimeoutSeconds)), nullptr);
      ZX_DEBUG_ASSERT_MSG(status == ZX_OK, "observer_event_.wait_one returned %s\n",
                          zx_status_get_string(status));
      observer_event_.signal(ZX_EVENT_SIGNALED, 0u);
    }

    if (mode_ == TRACE_BUFFERING_MODE_ONESHOT) {
      ZX_DEBUG_ASSERT(header.wrapped_count == 0);
    }
  }

 private:
  bool IsCategoryEnabled(const char* category) override {
    // Any category beginning with "+" is enabled.
    return category[0] == '+';
  }

  void TraceStopped(zx_status_t disposition) override {
    // This is noise if the status is ZX_OK, so just print if error.
    // There's also no point in printing for ZX_ERR_NO_MEMORY, as that
    // information can be determined from the number of records dropped.
    if (disposition != ZX_OK && disposition != ZX_ERR_NO_MEMORY) {
      printf("WARNING: Trace stopped, disposition = %s\n", zx_status_get_string(disposition));
    }

    if (mode_ == TRACE_BUFFERING_MODE_STREAMING) {
      ZX_DEBUG_ASSERT(disposition == ZX_OK ||
                      // Some records could have been dropped while
                      // "saving" the buffer.
                      disposition == ZX_ERR_NO_MEMORY);
    } else {
      // In oneshot and circular modes we shouldn't have dropped
      // any records.
      ZX_DEBUG_ASSERT(disposition == ZX_OK);
    }
  }

  void NotifyBufferFull(uint32_t wrapped_count, uint64_t durable_data_end) override {
    // We shouldn't get this in oneshot or circular modes.
    ZX_DEBUG_ASSERT(mode_ == TRACE_BUFFERING_MODE_STREAMING);

    // The intent isn't to include buffer-save time in the benchmarks,
    // so just immediately flag the buffer as saved. Alas since we're
    // running on a separate thread records may get dropped. It depends on
    // how well we're scheduled.
    trace_engine_mark_buffer_saved(wrapped_count, durable_data_end);
  }

  async::Loop* const loop_;
  const trace_buffering_mode_t mode_;
  fbl::Array<uint8_t> const buffer_;
  zx::event observer_event_;
};

#endif  // ZIRCON_SYSTEM_UAPP_TRACE_BENCHMARK_HANDLER_H_