Tracing pre-filtering

base/trace_event/trace_log.cc

Index: base/trace_event/trace_log.cc
diff --git a/base/trace_event/trace_log.cc b/base/trace_event/trace_log.cc
index cc40ba98eb31f5c0b5e370bacbf8ca5b232a15dd..39a74491892c1561c787692fc61058dcbae3612a 100644
--- a/base/trace_event/trace_log.cc
+++ b/base/trace_event/trace_log.cc
@@ -16,6 +16,7 @@
 #include "base/lazy_instance.h"
 #include "base/location.h"
 #include "base/macros.h"
+#include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/memory/singleton.h"
 #include "base/process/process_metrics.h"
@@ -102,6 +103,43 @@ const char* g_category_groups[MAX_CATEGORY_GROUPS] = {
 
 // The enabled flag is char instead of bool so that the API can be used from C.
 unsigned char g_category_group_enabled[MAX_CATEGORY_GROUPS] = {0};
+
+class TraceEventFilter {
+ public:
+  TraceEventFilter() {}
+  virtual ~TraceEventFilter() {}
+  virtual bool FilterTraceEvent(const TraceEvent& trace_event) const = 0;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(TraceEventFilter);
+};
+
+class EventNameFilter : public TraceEventFilter {
+ public:
+  EventNameFilter(const base::DictionaryValue* filter_args) {
+    const base::ListValue* whitelist = nullptr;
+    if (filter_args->GetList("event_name_whitelist", &whitelist)) {
+      for (size_t i = 0; i < whitelist->GetSize(); ++i) {
+        std::string event_name;
+        if (!whitelist->GetString(i, &event_name))
+          continue;
+
+        whitelist_.insert(event_name);
+      }
+    }
+  }
+
+  bool FilterTraceEvent(const TraceEvent& trace_event) const override {
+    return ContainsKey(whitelist_, trace_event.name());
+  }
+
+ private:
+  std::unordered_set<std::string> whitelist_;
+};
+
+base::LazyInstance<std::list<std::unique_ptr<TraceEventFilter>>>::Leaky
+    g_category_group_filter[MAX_CATEGORY_GROUPS] = {LAZY_INSTANCE_INITIALIZER};
+
 // Indexes here have to match the g_category_groups array indexes above.
 const int g_category_already_shutdown = 1;
 const int g_category_categories_exhausted = 2;
@@ -179,6 +217,22 @@ void MakeHandle(uint32_t chunk_seq,
   handle->event_index = static_cast<uint16_t>(event_index);
 }
 
+uintptr_t GetCategoryIndex(const unsigned char* category_group_enabled) {
+  // Calculate the index of the category group by finding
+  // category_group_enabled in g_category_group_enabled array.
+  uintptr_t category_begin =
+      reinterpret_cast<uintptr_t>(g_category_group_enabled);
+  uintptr_t category_ptr = reinterpret_cast<uintptr_t>(category_group_enabled);
+  DCHECK(category_ptr >= category_begin &&
+         category_ptr < reinterpret_cast<uintptr_t>(g_category_group_enabled +
+                                                    MAX_CATEGORY_GROUPS))
+      << "out of bounds category pointer";
+  uintptr_t category_index =
+      (category_ptr - category_begin) / sizeof(g_category_group_enabled[0]);
+
+  return category_index;
+}
+
 }  // namespace
 
 // A helper class that allows the lock to be acquired in the middle of the scope
@@ -445,18 +499,13 @@ const unsigned char* TraceLog::GetCategoryGroupEnabled(
 
 const char* TraceLog::GetCategoryGroupName(
     const unsigned char* category_group_enabled) {
-  // Calculate the index of the category group by finding
-  // category_group_enabled in g_category_group_enabled array.
-  uintptr_t category_begin =
-      reinterpret_cast<uintptr_t>(g_category_group_enabled);
-  uintptr_t category_ptr = reinterpret_cast<uintptr_t>(category_group_enabled);
-  DCHECK(category_ptr >= category_begin &&
-         category_ptr < reinterpret_cast<uintptr_t>(g_category_group_enabled +
-                                                    MAX_CATEGORY_GROUPS))
-      << "out of bounds category pointer";
-  uintptr_t category_index =
-      (category_ptr - category_begin) / sizeof(g_category_group_enabled[0]);
-  return g_category_groups[category_index];
+  return g_category_groups[GetCategoryIndex(category_group_enabled)];
+}
+
+std::list<std::unique_ptr<TraceEventFilter>>* GetCategoryGroupFilter(
+    const unsigned char* category_group_enabled) {
+  return g_category_group_filter[GetCategoryIndex(category_group_enabled)]
+      .Pointer();
 }
 
 void TraceLog::UpdateCategoryGroupEnabledFlag(size_t category_index) {
@@ -479,6 +528,28 @@ void TraceLog::UpdateCategoryGroupEnabledFlag(size_t category_index) {
   }
 #endif
 
+  // Having a filter is an exceptional case, so we avoid
+  // the LazyInstance creation in the common case.
+  if (!(g_category_group_filter[category_index] == nullptr))
+    g_category_group_filter[category_index].Get().clear();
+
+  for (const auto& event_filter : trace_config_.event_filters()) {
+    if (event_filter.IsCategoryGroupEnabled(category_group)) {
+      std::unique_ptr<TraceEventFilter> new_filter;
+
+      if (event_filter.predicate_name() == "event_whitelist_predicate") {
+        new_filter =
+            WrapUnique(new EventNameFilter(event_filter.filter_args()));
+      }
+
+      if (new_filter) {
+        g_category_group_filter[category_index].Get().push_back(
+            std::move(new_filter));
+        enabled_flag |= ENABLED_FOR_FILTERING;
+      }
+    }
+  }
+
   g_category_group_enabled[category_index] = enabled_flag;
 }
 
@@ -1270,7 +1341,32 @@ TraceEventHandle TraceLog::AddTraceEventWithThreadIdAndTimestamp(
 #endif  // OS_WIN
 
   std::string console_message;
-  if (*category_group_enabled & ENABLED_FOR_RECORDING) {
+  std::unique_ptr<TraceEvent> filtered_trace_event;
+  if (*category_group_enabled & ENABLED_FOR_FILTERING) {
+    std::unique_ptr<TraceEvent> new_trace_event(new TraceEvent);
+    new_trace_event->Initialize(thread_id, offset_event_timestamp, thread_now,
+                                phase, category_group_enabled, name, scope, id,
+                                bind_id, num_args, arg_names, arg_types,
+                                arg_values, convertable_values, flags);
+
+    auto filter_list = GetCategoryGroupFilter(category_group_enabled);
+    DCHECK(!filter_list->empty());
+
+    bool should_add_event = false;
+    for (const auto& trace_event_filter : *filter_list) {
+      if (trace_event_filter.get()->FilterTraceEvent(*new_trace_event))

[ssid, 2016/05/20 21:58:42]

I dont think ".get()" is needed here. Just 
trace_event_filter->FilterTraceEvent() ?

[oystein (OOO til 10th of July), 2016/05/24 01:05:13]

Done.

+        should_add_event = true;
+    }
+
+    if (should_add_event)
+      filtered_trace_event = std::move(new_trace_event);
+  }
+
+  // Add the trace event if we're either *just* recording (and not filtering)
+  // or if we one of our filters indicates the event should be added.
+  if (((*category_group_enabled & ENABLED_FOR_RECORDING) &&
+    (*category_group_enabled & ENABLED_FOR_FILTERING) == 0) ||
+      filtered_trace_event) {
     OptionalAutoLock lock(&lock_);
 
     TraceEvent* trace_event = NULL;
@@ -1282,21 +1378,14 @@ TraceEventHandle TraceLog::AddTraceEventWithThreadIdAndTimestamp(
     }
 
     if (trace_event) {
-      trace_event->Initialize(thread_id,
-                              offset_event_timestamp,
-                              thread_now,
-                              phase,
-                              category_group_enabled,
-                              name,
-                              scope,
-                              id,
-                              bind_id,
-                              num_args,
-                              arg_names,
-                              arg_types,
-                              arg_values,
-                              convertable_values,
-                              flags);
+      if (filtered_trace_event) {
+        trace_event->MoveFrom(std::move(filtered_trace_event));
+      } else {
+        trace_event->Initialize(thread_id, offset_event_timestamp, thread_now,
+                                phase, category_group_enabled, name, scope, id,
+                                bind_id, num_args, arg_names, arg_types,
+                                arg_values, convertable_values, flags);
+      }
 
 #if defined(OS_ANDROID)
       trace_event->SendToATrace();