[Lldb-commits] [lldb] [LLDB][Data Formatters] Calculate average and total time for summary providers within lldb (PR #102708)

[Michael Buch via lldb-commits]

================
@@ -174,6 +177,84 @@ struct StatisticsOptions {
   std::optional<bool> m_include_transcript;
 };
 
+/// A class that represents statistics about a TypeSummaryProviders invocations
+class SummaryStatistics {
+public:
+  explicit SummaryStatistics(lldb_private::ConstString name,
+                             lldb_private::ConstString impl_type)
+      : m_total_time(), m_impl_type(impl_type), m_name(name),
+        m_summary_count(0) {}
+
+  lldb_private::ConstString GetName() const { return m_name; };
+  double GetTotalTime() const { return m_total_time.get().count(); }
+
+  uint64_t GetSummaryCount() const {
+    return m_summary_count.load(std::memory_order_relaxed);
+  }
+
+  StatsDuration &GetDurationReference() { return m_total_time; }
+
+  ConstString GetImplType() const { return m_impl_type; }
+
+  llvm::json::Value ToJSON() const;
+
+  // Basic RAII class to increment the summary count when the call is complete.
+  // In the future this can be extended to collect information about the
+  // elapsed time for a single request.
+  class SummaryInvocation {
+  public:
+    SummaryInvocation(SummaryStatistics &summary)
+        : m_summary(summary), m_elapsed_time(summary.GetDurationReference()) {}
+    ~SummaryInvocation() { m_summary.OnInvoked(); }
+
+    // Delete the copy constructor and assignment operator to prevent
+    // accidental double counting.
+    SummaryInvocation(const SummaryInvocation &) = delete;
+    SummaryInvocation &operator=(const SummaryInvocation &) = delete;
+
+  private:
+    SummaryStatistics &m_summary;
+    ElapsedTime m_elapsed_time;
+  };
+
+  SummaryInvocation GetSummaryInvocation() { return SummaryInvocation(*this); }
+
+private:
+  /// Called when Summary Invocation is destructed.
+  void OnInvoked() noexcept {
+    m_summary_count.fetch_add(1, std::memory_order_relaxed);
+  }
+
+  lldb_private::StatsDuration m_total_time;
+  lldb_private::ConstString m_impl_type;
+  lldb_private::ConstString m_name;
+  std::atomic<uint64_t> m_summary_count;
+};
+
+/// A class that wraps a std::map of SummaryStatistics objects behind a mutex.
+class SummaryStatisticsCache {
+public:
+  /// Get the SummaryStatistics object for a given provider name, or insert
+  /// if statistics for that provider is not in the map.
+  lldb_private::SummaryStatistics &
+  GetSummaryStatisticsForProviderName(lldb_private::TypeSummaryImpl &provider) {
+    std::lock_guard<std::recursive_mutex> guard(m_map_mutex);
+    m_summary_stats_map.try_emplace(provider.GetName(), provider.GetName(),
+                                    provider.GetImplType());
+
+    SummaryStatistics &summary_stats =
+        m_summary_stats_map.at(provider.GetName());
+    return summary_stats;
+  }
+
+  llvm::json::Value ToJSON();
+
+private:
+  std::map<lldb_private::ConstString, lldb_private::SummaryStatistics>
+      m_summary_stats_map;
----------------
Michael137 wrote:

If we're going to be handing out references to members of the map, we need to make sure nothing invalidates them. Off the top of my head I'm not sure what iterator/reference invalidation guarantees `StringMap` has, but just from a brief skim of the file I saw the word "rehash", which makes me think reference might get stale after enough calls to `GetSummaryStatisticsForProviderName`

https://github.com/llvm/llvm-project/pull/102708