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 1a375d146a9eb20582e7948677029c93c6a1842f..6cfa5effef98864378e197804cd586fb69181f7b 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 +103,48 @@ 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(const base::DictionaryValue* filter_args) {}
+  virtual bool FilterTraceEvent(const TraceEvent& trace_event) const = 0;

[shatch, 2016/05/04 19:57:38]

Did we come to a decision on whether to allow the predicates to mutate the
events?

+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(TraceEventFilter);
+};
+
+class EventNameFilter : public TraceEventFilter {
+ public:
+  EventNameFilter(const base::DictionaryValue* filter_args)
+      : TraceEventFilter(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_.push_back(event_name);
+      }
+    }
+  }
+
+  bool FilterTraceEvent(const TraceEvent& trace_event) const override {
+    for (const auto& entry : whitelist_) {
+      if (trace_event.name() == entry)
+        return true;
+    }
+
+    return false;
+  }
+
+ private:
+  std::vector<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;
@@ -434,8 +477,8 @@ const unsigned char* TraceLog::GetCategoryGroupEnabled(
   return tracelog->GetCategoryGroupEnabledInternal(category_group);
 }
 
-const char* TraceLog::GetCategoryGroupName(
-    const unsigned char* category_group_enabled) {
+namespace {
+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 =
@@ -447,7 +490,20 @@ const char* TraceLog::GetCategoryGroupName(
       << "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 category_index;
+}
+}
+
+const char* TraceLog::GetCategoryGroupName(
+    const unsigned char* category_group_enabled) {
+  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) {
@@ -470,6 +526,27 @@ void TraceLog::UpdateCategoryGroupEnabledFlag(size_t category_index) {
   }
 #endif
 
+  if (!(g_category_group_filter[category_index] == nullptr))
+    g_category_group_filter[category_index].Get().clear();
+
+  for (const auto& category_event_filter :
+       trace_config_.GetCategoryEventFilters()) {
+    if (category_event_filter.IsCategoryGroupEnabled(category_group)) {
+      std::unique_ptr<TraceEventFilter> new_filter;
+
+      if (category_event_filter.predicate_name == "event_whitelist_predicate") {
+        new_filter =
+            WrapUnique(new EventNameFilter(category_event_filter.args.get()));
+      }
+
+      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;
 }
 
@@ -1247,7 +1324,39 @@ TraceEventHandle TraceLog::AddTraceEventWithThreadIdAndTimestamp(
 #endif  // OS_WIN
 
   std::string console_message;
-  if (*category_group_enabled & ENABLED_FOR_RECORDING) {
+  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);
+
+    std::list<std::unique_ptr<TraceEventFilter>>* filter_list =
+        GetCategoryGroupFilter(category_group_enabled);
+    DCHECK(filter_list);
+    DCHECK(!filter_list->empty());
+
+    bool should_add_event = false;
+    for (const auto& trace_event_filter : *filter_list) {
+      DCHECK(trace_event_filter);
+      if (trace_event_filter.get()->FilterTraceEvent(*new_trace_event))
+        should_add_event = true;
+    }
+
+    if (should_add_event) {
+      OptionalAutoLock lock(&lock_);
+
+      TraceEvent* trace_event = NULL;
+      if (thread_local_event_buffer) {
+        trace_event = thread_local_event_buffer->AddTraceEvent(&handle);
+      } else {
+        lock.EnsureAcquired();
+        trace_event = AddEventToThreadSharedChunkWhileLocked(&handle, true);
+      }
+
+      trace_event->MoveFrom(std::move(new_trace_event));
+    }
+  } else if (*category_group_enabled & ENABLED_FOR_RECORDING) {
     OptionalAutoLock lock(&lock_);
 
     TraceEvent* trace_event = NULL;