More precompute

src/metric.cpp

@@ -585,6 +585,152 @@ struct Metric {
     result.p = ptr;
     return result;
   }
+
+  // Pre-computed data structures with resolved pointers to eliminate hash
+  // lookups
+  struct CounterLabelData {
+    LabelsKey labels_key;
+    std::vector<Counter::State *> thread_states; // Pre-resolved pointers
+    Counter::State *global_state; // Pre-resolved global state pointer
+
+    CounterLabelData(const LabelsKey &key)
+        : labels_key(key), global_state(nullptr) {}
+  };
+
+  struct GaugeLabelData {
+    LabelsKey labels_key;
+    Gauge::State *instance_state; // Direct pointer to gauge instance
+
+    GaugeLabelData(const LabelsKey &key)
+        : labels_key(key), instance_state(nullptr) {}
+  };
+
+  struct HistogramLabelData {
+    LabelsKey labels_key;
+    std::vector<Histogram::State *> thread_states; // Pre-resolved pointers
+    Histogram::State *global_state; // Pre-resolved global state pointer
+    size_t bucket_count;            // Cache bucket count from family
+
+    HistogramLabelData(const LabelsKey &key)
+        : labels_key(key), global_state(nullptr), bucket_count(0) {}
+  };
+
+  // Pre-computed data for each family type, built once and reused
+  struct LabelSets {
+    std::vector<std::vector<CounterLabelData>> counter_data;
+    std::vector<std::vector<GaugeLabelData>> gauge_data;
+    std::vector<std::vector<HistogramLabelData>> histogram_data;
+  };
+
+  // Build label sets once for reuse in both phases
+  static LabelSets build_label_sets(ArenaAllocator &arena) {
+    LabelSets label_sets;
+
+    // Build counter data with pre-resolved pointers
+    for (const auto &[name, family] : Metric::get_counter_families()) {
+      // Collect all unique labels first
+      std::set<LabelsKey, std::less<LabelsKey>, ArenaStlAllocator<LabelsKey>>
+          all_labels{ArenaStlAllocator<LabelsKey>(&arena)};
+
+      for (const auto &[thread_id, per_thread] : family->per_thread_state) {
+        for (const auto &[labels_key, instance] : per_thread.instances) {
+          all_labels.insert(labels_key);
+        }
+      }
+      for (const auto &[labels_key, global_state] :
+           family->global_accumulated_values) {
+        if (global_state) {
+          all_labels.insert(labels_key);
+        }
+      }
+
+      // Pre-resolve all pointers for each label set
+      std::vector<CounterLabelData> family_data;
+      for (const auto &labels_key : all_labels) {
+        CounterLabelData data(labels_key);
+
+        // Pre-resolve thread-local state pointers
+        for (const auto &[thread_id, per_thread] : family->per_thread_state) {
+          auto it = per_thread.instances.find(labels_key);
+          if (it != per_thread.instances.end()) {
+            data.thread_states.push_back(it->second);
+          }
+        }
+
+        // Pre-resolve global accumulated state pointer
+        auto global_it = family->global_accumulated_values.find(labels_key);
+        data.global_state =
+            (global_it != family->global_accumulated_values.end() &&
+             global_it->second)
+                ? global_it->second
+                : nullptr;
+
+        family_data.push_back(std::move(data));
+      }
+      label_sets.counter_data.push_back(std::move(family_data));
+    }
+
+    // Build gauge data with pre-resolved pointers
+    for (const auto &[name, family] : Metric::get_gauge_families()) {
+      std::vector<GaugeLabelData> family_data;
+
+      // Gauges iterate directly over instances
+      for (const auto &[labels_key, instance] : family->instances) {
+        GaugeLabelData data(labels_key);
+        data.instance_state = instance;
+        family_data.push_back(std::move(data));
+      }
+
+      label_sets.gauge_data.push_back(std::move(family_data));
+    }
+
+    // Build histogram data with pre-resolved pointers
+    for (const auto &[name, family] : Metric::get_histogram_families()) {
+      // Collect all unique labels first
+      std::set<LabelsKey, std::less<LabelsKey>, ArenaStlAllocator<LabelsKey>>
+          all_labels{ArenaStlAllocator<LabelsKey>(&arena)};
+
+      for (const auto &[thread_id, per_thread] : family->per_thread_state) {
+        for (const auto &[labels_key, instance] : per_thread.instances) {
+          all_labels.insert(labels_key);
+        }
+      }
+      for (const auto &[labels_key, global_state] :
+           family->global_accumulated_values) {
+        if (global_state) {
+          all_labels.insert(labels_key);
+        }
+      }
+
+      // Pre-resolve all pointers for each label set
+      std::vector<HistogramLabelData> family_data;
+      for (const auto &labels_key : all_labels) {
+        HistogramLabelData data(labels_key);
+        data.bucket_count = family->buckets.size(); // Cache bucket count
+
+        // Pre-resolve thread-local state pointers
+        for (const auto &[thread_id, per_thread] : family->per_thread_state) {
+          auto it = per_thread.instances.find(labels_key);
+          if (it != per_thread.instances.end()) {
+            data.thread_states.push_back(it->second);
+          }
+        }
+
+        // Pre-resolve global accumulated state pointer
+        auto global_it = family->global_accumulated_values.find(labels_key);
+        data.global_state =
+            (global_it != family->global_accumulated_values.end() &&
+             global_it->second)
+                ? global_it->second
+                : nullptr;
+
+        family_data.push_back(std::move(data));
+      }
+      label_sets.histogram_data.push_back(std::move(family_data));
+    }
+
+    return label_sets;
+  }
 };
 
 Counter::Counter() = default;
@@ -928,79 +1074,10 @@ union MetricValue {
   uint64_t as_uint64;
 };
 
-// Label sets for each family type, built once and reused
-struct LabelSets {
-  std::vector<
-      std::set<LabelsKey, std::less<LabelsKey>, ArenaStlAllocator<LabelsKey>>>
-      counter_labels;
-  std::vector<
-      std::set<LabelsKey, std::less<LabelsKey>, ArenaStlAllocator<LabelsKey>>>
-      gauge_labels;
-  std::vector<
-      std::set<LabelsKey, std::less<LabelsKey>, ArenaStlAllocator<LabelsKey>>>
-      histogram_labels;
-};
-
-// Build label sets once for reuse in both phases
-static LabelSets build_label_sets(ArenaAllocator &arena) {
-  LabelSets label_sets;
-
-  // Build counter label sets
-  for (const auto &[name, family] : Metric::get_counter_families()) {
-    std::set<LabelsKey, std::less<LabelsKey>, ArenaStlAllocator<LabelsKey>>
-        all_labels{ArenaStlAllocator<LabelsKey>(&arena)};
-
-    for (const auto &[thread_id, per_thread] : family->per_thread_state) {
-      for (const auto &[labels_key, instance] : per_thread.instances) {
-        all_labels.insert(labels_key);
-      }
-    }
-    for (const auto &[labels_key, global_state] :
-         family->global_accumulated_values) {
-      if (global_state) {
-        all_labels.insert(labels_key);
-      }
-    }
-
-    label_sets.counter_labels.push_back(std::move(all_labels));
-  }
-
-  // Build gauge label sets (none needed - gauges iterate directly over
-  // instances)
-  for (const auto &[name, family] : Metric::get_gauge_families()) {
-    (void)name;
-    (void)family; // Suppress unused variable warnings
-    std::set<LabelsKey, std::less<LabelsKey>, ArenaStlAllocator<LabelsKey>>
-        empty_set{ArenaStlAllocator<LabelsKey>(&arena)};
-    label_sets.gauge_labels.push_back(std::move(empty_set));
-  }
-
-  // Build histogram label sets
-  for (const auto &[name, family] : Metric::get_histogram_families()) {
-    std::set<LabelsKey, std::less<LabelsKey>, ArenaStlAllocator<LabelsKey>>
-        all_labels{ArenaStlAllocator<LabelsKey>(&arena)};
-
-    for (const auto &[thread_id, per_thread] : family->per_thread_state) {
-      for (const auto &[labels_key, instance] : per_thread.instances) {
-        all_labels.insert(labels_key);
-      }
-    }
-    for (const auto &[labels_key, global_state] :
-         family->global_accumulated_values) {
-      if (global_state) {
-        all_labels.insert(labels_key);
-      }
-    }
-
-    label_sets.histogram_labels.push_back(std::move(all_labels));
-  }
-
-  return label_sets;
-}
-
 // Phase 1: Compute all metric values in deterministic order
 static ArenaVector<MetricValue>
-compute_metric_values(ArenaAllocator &arena, const LabelSets &label_sets) {
+compute_metric_values(ArenaAllocator &arena,
+                      const Metric::LabelSets &label_sets) {
   ArenaVector<MetricValue> values(&arena);
 
   // Compute counter values - ITERATION ORDER MUST MATCH FORMAT PHASE
@@ -1012,29 +1089,22 @@ compute_metric_values(ArenaAllocator &arena, const LabelSets &label_sets) {
       values.push_back({.as_double = value});
     }
 
-    // Use pre-built label sets
+    // Use pre-computed data with resolved pointers - no hash lookups!
-    const auto &all_labels = label_sets.counter_labels[counter_family_idx++];
+    const auto &family_data = label_sets.counter_data[counter_family_idx++];
-
+    for (const auto &data : family_data) {
-    // Iterate by label, lookup per thread (O(1) unordered_map lookup)
-    for (const auto &labels_key : all_labels) {
       double total_value = 0.0;
 
-      // Sum thread-local values for this label set
+      // Sum thread-local values using pre-resolved pointers
-      for (const auto &[thread_id, per_thread] : family->per_thread_state) {
+      for (auto *state_ptr : data.thread_states) {
-        auto it = per_thread.instances.find(labels_key);
-        if (it != per_thread.instances.end()) {
         // Atomic read to match atomic store in Counter::inc()
         double value;
-          __atomic_load(&it->second->value, &value, __ATOMIC_RELAXED);
+        __atomic_load(&state_ptr->value, &value, __ATOMIC_RELAXED);
         total_value += value;
       }
-      }
 
-      // Add global accumulated value for this label set
+      // Add global accumulated value using pre-resolved pointer
-      auto global_it = family->global_accumulated_values.find(labels_key);
+      if (data.global_state) {
-      if (global_it != family->global_accumulated_values.end() &&
+        total_value += data.global_state->value;
-          global_it->second) {
-        total_value += global_it->second->value;
       }
 
       values.push_back({.as_double = total_value});
@@ -1042,6 +1112,7 @@ compute_metric_values(ArenaAllocator &arena, const LabelSets &label_sets) {
   }
 
   // Compute gauge values - ITERATION ORDER MUST MATCH FORMAT PHASE
+  size_t gauge_family_idx = 0;
   for (const auto &[name, family] : Metric::get_gauge_families()) {
     // Callback values
     for (const auto &[labels_key, callback] : family->callbacks) {
@@ -1049,25 +1120,23 @@ compute_metric_values(ArenaAllocator &arena, const LabelSets &label_sets) {
       values.push_back({.as_double = value});
     }
 
-    // Instance values (gauges don't aggregate, just direct values)
+    // Use pre-computed data with resolved pointers - no hash lookups!
-    for (const auto &[labels_key, instance] : family->instances) {
+    const auto &family_data = label_sets.gauge_data[gauge_family_idx++];
+    for (const auto &data : family_data) {
       auto value = std::bit_cast<double>(
-          instance->value.load(std::memory_order_relaxed));
+          data.instance_state->value.load(std::memory_order_relaxed));
       values.push_back({.as_double = value});
     }
   }
 
   // Compute histogram values - ITERATION ORDER MUST MATCH FORMAT PHASE
   size_t histogram_family_idx = 0;
-  for (const auto &[name, family] : Metric::get_histogram_families()) {
+  for (const auto &family_pair : Metric::get_histogram_families()) {
-    // Use pre-built label sets
+    // Use pre-computed data with resolved pointers - no hash lookups!
-    const auto &all_labels =
+    const auto &family_data = label_sets.histogram_data[histogram_family_idx++];
-        label_sets.histogram_labels[histogram_family_idx++];
 
-    // Iterate by label, lookup per thread (O(1) unordered_map lookup)
+    for (const auto &data : family_data) {
-    for (const auto &labels_key : all_labels) {
+      size_t bucket_count = data.bucket_count; // Use cached bucket count
-      // Get bucket count from family config or first instance
-      size_t bucket_count = family->buckets.size();
 
       ArenaVector<uint64_t> total_counts(&arena);
       for (size_t i = 0; i < bucket_count; ++i) {
@@ -1076,12 +1145,8 @@ compute_metric_values(ArenaAllocator &arena, const LabelSets &label_sets) {
       double total_sum = 0.0;
       uint64_t total_observations = 0;
 
-      // Sum thread-local values for this label set
+      // Sum thread-local values using pre-resolved pointers
-      for (const auto &[thread_id, per_thread] : family->per_thread_state) {
+      for (auto *instance : data.thread_states) {
-        auto it = per_thread.instances.find(labels_key);
-        if (it != per_thread.instances.end()) {
-          auto *instance = it->second;
-
         // Extract data under lock - minimize critical section
         uint64_t *counts_snapshot = arena.allocate<uint64_t>(bucket_count);
         double sum_snapshot;
@@ -1103,13 +1168,10 @@ compute_metric_values(ArenaAllocator &arena, const LabelSets &label_sets) {
         total_sum += sum_snapshot;
         total_observations += observations_snapshot;
       }
-      }
 
-      // Add global accumulated value for this label set
+      // Add global accumulated value using pre-resolved pointer
-      auto global_it = family->global_accumulated_values.find(labels_key);
+      if (data.global_state) {
-      if (global_it != family->global_accumulated_values.end() &&
+        auto *global_state = data.global_state;
-          global_it->second) {
-        auto *global_state = global_it->second;
         for (size_t i = 0; i < global_state->counts.size(); ++i) {
           total_counts[i] += global_state->counts[i];
         }
@@ -1140,7 +1202,7 @@ std::span<std::string_view> render(ArenaAllocator &arena) {
   std::unique_lock<std::mutex> _{Metric::mutex};
 
   // Build label sets once for both phases
-  LabelSets label_sets = build_label_sets(arena);
+  Metric::LabelSets label_sets = Metric::build_label_sets(arena);
 
   // Phase 1: Compute all metric values
   ArenaVector<MetricValue> metric_values =
@@ -1232,15 +1294,15 @@ std::span<std::string_view> render(ArenaAllocator &arena) {
                               value));
     }
 
-    // Use pre-built label sets (same as compute phase)
+    // Use pre-computed data (same as compute phase)
-    const auto &all_labels = label_sets.counter_labels[counter_family_idx++];
+    const auto &family_data = label_sets.counter_data[counter_family_idx++];
 
     // Format counter values using pre-computed values
-    for (const auto &labels_key : all_labels) {
+    for (const auto &data : family_data) {
       auto total_value = next_value++->as_double;
       labels_sv.clear();
-      for (size_t i = 0; i < labels_key.labels.size(); ++i) {
+      for (size_t i = 0; i < data.labels_key.labels.size(); ++i) {
-        labels_sv.push_back(labels_key.labels[i]);
+        labels_sv.push_back(data.labels_key.labels[i]);
       }
       auto labels = format_labels(labels_sv);
       output.push_back(format(arena, "%.*s%.*s %.17g\n",
@@ -1251,6 +1313,7 @@ std::span<std::string_view> render(ArenaAllocator &arena) {
   }
 
   // Format gauges - ITERATION ORDER MUST MATCH COMPUTE PHASE
+  size_t gauge_family_idx = 0;
   for (const auto &[name, family] : Metric::get_gauge_families()) {
     output.push_back(format(arena, "# HELP %.*s %.*s\n",
                             static_cast<int>(name.length()), name.data(),
@@ -1276,12 +1339,13 @@ std::span<std::string_view> render(ArenaAllocator &arena) {
                               value));
     }
 
-    // Format instance values
+    // Use pre-computed data (same as compute phase)
-    for (const auto &[labels_key, instance] : family->instances) {
+    const auto &family_data = label_sets.gauge_data[gauge_family_idx++];
+    for (const auto &data : family_data) {
       auto value = next_value++->as_double;
       labels_sv.clear();
-      for (size_t i = 0; i < labels_key.labels.size(); ++i) {
+      for (size_t i = 0; i < data.labels_key.labels.size(); ++i) {
-        labels_sv.push_back(labels_key.labels[i]);
+        labels_sv.push_back(data.labels_key.labels[i]);
       }
       auto labels = format_labels(labels_sv);
       output.push_back(format(arena, "%.*s%.*s %.17g\n",
@@ -1301,24 +1365,23 @@ std::span<std::string_view> render(ArenaAllocator &arena) {
     output.push_back(format(arena, "# TYPE %.*s histogram\n",
                             static_cast<int>(name.length()), name.data()));
 
-    // Use pre-built label sets (same as compute phase)
+    // Use pre-computed data (same as compute phase)
-    const auto &all_labels =
+    const auto &family_data = label_sets.histogram_data[histogram_family_idx++];
-        label_sets.histogram_labels[histogram_family_idx++];
 
     ArenaVector<std::pair<std::string_view, std::string_view>> bucket_labels_sv(
         &arena);
 
     // Format histogram data using pre-computed values
-    for (const auto &labels_key : all_labels) {
+    for (const auto &data : family_data) {
-      // Get bucket thresholds from family config
+      // Get bucket count from pre-computed data
-      size_t bucket_count = family->buckets.size();
+      size_t bucket_count = data.bucket_count;
 
       // Format explicit bucket counts
       for (size_t i = 0; i < bucket_count; ++i) {
         auto count = next_value++->as_uint64;
         bucket_labels_sv.clear();
-        for (size_t j = 0; j < labels_key.labels.size(); ++j) {
+        for (size_t j = 0; j < data.labels_key.labels.size(); ++j) {
-          bucket_labels_sv.push_back(labels_key.labels[j]);
+          bucket_labels_sv.push_back(data.labels_key.labels[j]);
         }
         bucket_labels_sv.push_back(
             {"le", static_format(arena, family->buckets[i])});
@@ -1332,8 +1395,8 @@ std::span<std::string_view> render(ArenaAllocator &arena) {
       // Format +Inf bucket
       auto observations = next_value++->as_uint64;
       bucket_labels_sv.clear();
-      for (size_t j = 0; j < labels_key.labels.size(); ++j) {
+      for (size_t j = 0; j < data.labels_key.labels.size(); ++j) {
-        bucket_labels_sv.push_back(labels_key.labels[j]);
+        bucket_labels_sv.push_back(data.labels_key.labels[j]);
       }
       bucket_labels_sv.push_back({"le", "+Inf"});
       auto inf_labels = format_labels(bucket_labels_sv);
@@ -1345,8 +1408,8 @@ std::span<std::string_view> render(ArenaAllocator &arena) {
       // Format sum
       auto sum = next_value++->as_double;
       bucket_labels_sv.clear();
-      for (size_t j = 0; j < labels_key.labels.size(); ++j) {
+      for (size_t j = 0; j < data.labels_key.labels.size(); ++j) {
-        bucket_labels_sv.push_back(labels_key.labels[j]);
+        bucket_labels_sv.push_back(data.labels_key.labels[j]);
       }
       auto labels = format_labels(bucket_labels_sv);
       output.push_back(format(