Make Chrome Trace work with Android ATrace.

base/debug/trace_event_android.cc

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/debug/trace_event_impl.h"
+
+#include <fcntl.h>
+
+#include "base/debug/trace_event.h"
+#include "base/file_util.h"
+#include "base/format_macros.h"
+#include "base/logging.h"
+#include "base/stringprintf.h"
+
+namespace {
+
+int g_atrace_fd = -1;
+const char* kATraceMarkerFile = "/sys/kernel/debug/tracing/trace_marker";
+
+}  // namespace
+
+namespace base {
+namespace debug {
+
+// static
+void TraceLog::InitATrace() {
+  DCHECK(g_atrace_fd == -1);
+  g_atrace_fd = open(kATraceMarkerFile, O_WRONLY | O_APPEND);
+  if (g_atrace_fd == -1)
+    LOG(WARNING) << "Couldn't open " << kATraceMarkerFile;
+}
+
+// static
+bool TraceLog::IsATraceEnabled() {
+  return g_atrace_fd != -1;
+}
+
+void TraceLog::SendToATrace(char phase,
+                            const char* category,
+                            const char* name,
+                            int num_args,
+                            const char** arg_names,
+                            const unsigned char* arg_types,
+                            const unsigned long long* arg_values) {
+  if (!IsATraceEnabled())
+    return;
+
+  switch (phase) {
+    case TRACE_EVENT_PHASE_BEGIN:
+    case TRACE_EVENT_PHASE_INSTANT: {
+      std::string out = StringPrintf("B|%d|%s-%s", getpid(), category, name);

[jbates, 2012/10/30 20:22:14]

There's plenty of room for performance improvements here, fyi

[Xianzhu, 2012/10/30 21:45:01]

Could you be more specific? Do you mean the "+=", not using StringPrintf, or sth
else?

[jbates, 2012/10/31 22:26:01]

Yep, StringPrintf and std::string temporaries are inefficient. JSON conversion
below probably trumps it all though so I'm assuming you haven't ran into a
problem with performance. It's no worse than Java I guess ;)

+      for (int i = 0; i < num_args; ++i) {
+        out += '|';
+        out += arg_names[i];
+        out += '=';
+        TraceEvent::TraceValue value;
+        value.as_uint = arg_values[i];
+        std::string::size_type value_start = out.length();
+        TraceEvent::AppendValueAsJSON(arg_types[i], value, &out);
+        // Remove the quotes which may confuse the atrace script.
+        ReplaceSubstringsAfterOffset(&out, value_start, "\\\"", "'");
+        ReplaceSubstringsAfterOffset(&out, value_start, "\"", "");
+      }
+      write(g_atrace_fd, out.c_str(), out.size());
+
+      if (phase != TRACE_EVENT_PHASE_INSTANT)
+        break;
+      // Fall through. Simulate an instance event with a pair of begin/end.
+    }
+    case TRACE_EVENT_PHASE_END: {
+      // Though a single 'E' is enough, here append pid and name so that
+      // unpaired events can be found easily.
+      std::string out = StringPrintf("E|%d|%s-%s", getpid(), category, name);
+      write(g_atrace_fd, out.c_str(), out.size());
+      break;
+    }
+    case TRACE_EVENT_PHASE_COUNTER:
+      for (int i = 0; i < num_args; ++i) {
+        DCHECK(arg_types[i] == TRACE_VALUE_TYPE_INT);
+        std::string out = StringPrintf(
+            "C|%d|%s-%s-%s|%d",
+            getpid(), category, name,
+            arg_names[i], static_cast<int>(arg_values[i]));
+        write(g_atrace_fd, out.c_str(), out.size());
+      }
+      break;
+
+    default:
+      // Do nothing.
+      break;
+  }
+}
+
+void TraceLog::AddClockSyncMetadataEvents() {
+  // Since Android does not support sched_setaffinity, we cannot establish clock
+  // sync unless the scheduler clock is set to global. If the trace_clock file
+  // can't be read, we will assume the kernel doesn't support tracing and do
+  // nothing.
+  std::string clock_mode;
+  if (!file_util::ReadFileToString(
+      FilePath("/sys/kernel/debug/tracing/trace_clock"), &clock_mode))
+    return;
+
+  if (clock_mode != "local [global]\n") {
+    DLOG(WARNING) <<
+        "The kernel's tracing clock must be set to global in order for " <<
+        "trace_event to be synchronized with . Do this by\n" <<
+        "  echo global > /sys/kerel/debug/tracing/trace_clock";
+    return;
+  }
+
+  int atrace_fd = g_atrace_fd;
+  if (atrace_fd == -1) {
+    // This function may be called when atrace is not enabled.
+    atrace_fd = open(kATraceMarkerFile, O_WRONLY | O_APPEND);
+    if (atrace_fd == -1) {
+      LOG(WARNING) << "Couldn't open " << kATraceMarkerFile;
+      return;
+    }
+  }
+
+  // Android's kernel trace system has a trace_marker feature: this is a file on
+  // debugfs that takes the written data and pushes it onto the trace
+  // buffer. So, to establish clock sync, we write our monotonic clock into that
+  // trace buffer.
+  TimeTicks now = TimeTicks::NowFromSystemTraceTime();
+  double now_in_seconds = now.ToInternalValue() / 1000000.0;
+  std::string marker = StringPrintf(
+      "trace_event_clock_sync: parent_ts=%f\n", now_in_seconds);
+  if (write(atrace_fd, marker.c_str(), marker.size()) != 0) {
+    DLOG(WARNING) << "Couldn't write to " << kATraceMarkerFile << ": "
+                  << strerror(errno);
+  }
+
+  if (g_atrace_fd == -1)
+    close(atrace_fd);
+}
+
+}  // namespace debug
+}  // namespace base