Propose a metrics interface

ConflictSet.cpp

@@ -546,7 +546,38 @@ static_assert(kBytesPerKey - sizeof(Node0) >= kMinNodeSurplus);
 
 constexpr int64_t kFreeListMaxMemory = 1 << 20;
 
+struct Metric {
+  Metric *prev;
+  const char *name;
+  const char *help;
+  ConflictSet::MetricsV1::Type type;
+  double value;
+
+protected:
+  Metric(ConflictSet::Impl *impl, const char *name, const char *help,
+         ConflictSet::MetricsV1::Type type);
+};
+
+struct Gauge : private Metric {
+  Gauge(ConflictSet::Impl *impl, const char *name, const char *help)
+      : Metric(impl, name, help, ConflictSet::MetricsV1::Gauge) {}
+
+  void set(double value) { this->value = value; }
+};
+
+struct Counter : private Metric {
+  Counter(ConflictSet::Impl *impl, const char *name, const char *help)
+      : Metric(impl, name, help, ConflictSet::MetricsV1::Counter) {}
+  void add(double value) {
+    assert(value >= 0);
+    this->value += value;
+  }
+};
+
 template <class T> struct BoundedFreeListAllocator {
+  Counter *allocated_total = nullptr;
+  Counter *released_total = nullptr;
+
   static_assert(sizeof(T) >= sizeof(void *));
   static_assert(std::derived_from<T, Node>);
   static_assert(std::is_trivial_v<T>);
@@ -580,6 +611,7 @@ template <class T> struct BoundedFreeListAllocator {
   }
 
   T *allocate(int partialKeyCapacity) {
+    allocated_total->add(1);
     T *result = allocate_helper(partialKeyCapacity);
     if constexpr (!std::is_same_v<T, Node0>) {
       memset(result->children, 0, sizeof(result->children));
@@ -596,6 +628,7 @@ template <class T> struct BoundedFreeListAllocator {
   }
 
   void release(T *p) {
+    released_total->add(1);
     if (freeListBytes >= kFreeListMaxMemory) {
       removeNode(p);
       return safe_free(p, sizeof(T) + p->partialKeyCapacity);
@@ -3136,6 +3169,16 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
 
     allocators.~NodeAllocators();
     new (&allocators) NodeAllocators();
+    allocators.node0.allocated_total = &node0_allocated_total;
+    allocators.node3.allocated_total = &node3_allocated_total;
+    allocators.node16.allocated_total = &node16_allocated_total;
+    allocators.node48.allocated_total = &node48_allocated_total;
+    allocators.node256.allocated_total = &node256_allocated_total;
+    allocators.node0.released_total = &node0_released_total;
+    allocators.node3.released_total = &node3_released_total;
+    allocators.node16.released_total = &node16_released_total;
+    allocators.node48.released_total = &node48_released_total;
+    allocators.node256.released_total = &node256_released_total;
 
     removalKeyArena = Arena{};
     removalKey = {};
@@ -3160,8 +3203,14 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
     // Intentionally not resetting totalBytes
   }
 
-  explicit Impl(int64_t oldestVersion) { init(oldestVersion); }
-  ~Impl() { destroyTree(root); }
+  explicit Impl(int64_t oldestVersion) {
+    init(oldestVersion);
+    initMetrics();
+  }
+  ~Impl() {
+    destroyTree(root);
+    safe_free(metrics, metricsCount * sizeof(metrics[0]));
+  }
 
   NodeAllocators allocators;
 
@@ -3177,8 +3226,63 @@ struct __attribute__((visibility("hidden"))) ConflictSet::Impl {
   int64_t oldestVersionAtGcBegin;
   int64_t newestVersionFullPrecision;
   int64_t totalBytes = 0;
+
+  MetricsV1 *metrics;
+  int metricsCount = 0;
+  void initMetrics() {
+    metrics = (MetricsV1 *)safe_malloc(metricsCount * sizeof(metrics[0]));
+    for (auto [i, m] = std::make_tuple(0, metricList); i < metricsCount;
+         ++i, m = m->prev) {
+      metrics[i].name = m->name;
+      metrics[i].help = m->help;
+      metrics[i].value = &m->value;
+      metrics[i].type = m->type;
+    }
+    std::sort(metrics, metrics + metricsCount,
+              [](const MetricsV1 &lhs, const MetricsV1 &rhs) -> bool {
+                return std::string_view(lhs.name) < std::string_view(rhs.name);
+              });
+  }
+
+  Metric *metricList = nullptr;
+
+#define GAUGE(name, help)                                                      \
+  Gauge name { this, #name, help }
+#define COUNTER(name, help)                                                    \
+  Counter name { this, #name, help }
+  // ==================== METRICS DEFINITIONS ====================
+  COUNTER(node0_allocated_total,
+          "Total number of nodes of type \"Node0\" that have been allocated");
+  COUNTER(node3_allocated_total,
+          "Total number of nodes of type \"Node3\" that have been allocated");
+  COUNTER(node16_allocated_total,
+          "Total number of nodes of type \"Node16\" that have been allocated");
+  COUNTER(node48_allocated_total,
+          "Total number of nodes of type \"Node48\" that have been allocated");
+  COUNTER(node256_allocated_total,
+          "Total number of nodes of type \"Node256\" that have been allocated");
+  COUNTER(node0_released_total,
+          "Total number of nodes of type \"Node0\" that have been released");
+  COUNTER(node3_released_total,
+          "Total number of nodes of type \"Node3\" that have been released");
+  COUNTER(node16_released_total,
+          "Total number of nodes of type \"Node16\" that have been released");
+  COUNTER(node48_released_total,
+          "Total number of nodes of type \"Node48\" that have been released");
+  COUNTER(node256_released_total,
+          "Total number of nodes of type \"Node256\" that have been released");
+  // ==================== END METRICS DEFINITIONS ====================
+#undef GAUGE
+#undef COUNTER
 };
 
+Metric::Metric(ConflictSet::Impl *impl, const char *name, const char *help,
+               ConflictSet::MetricsV1::Type type)
+    : prev(std::exchange(impl->metricList, this)), name(name), help(help),
+      type(type), value(0) {
+  ++impl->metricsCount;
+}
+
 InternalVersionT maxVersion(Node *n, ConflictSet::Impl *impl) {
   int index = n->parentsIndex;
   n = n->parent;
@@ -3308,6 +3412,12 @@ void internal_destroy(ConflictSet::Impl *impl) {
 
 int64_t internal_getBytes(ConflictSet::Impl *impl) { return impl->getBytes(); }
 
+void internal_getMetricsV1(ConflictSet::Impl *impl,
+                           ConflictSet::MetricsV1 **metrics, int *count) {
+  *metrics = impl->metrics;
+  *count = impl->metricsCount;
+}
+
 // ==================== END IMPLEMENTATION ====================
 
 // GCOVR_EXCL_START
@@ -3392,6 +3502,10 @@ void ConflictSet::setOldestVersion(int64_t oldestVersion) {
 
 int64_t ConflictSet::getBytes() const { return internal_getBytes(impl); }
 
+void ConflictSet::getMetricsV1(MetricsV1 **metrics, int *count) const {
+  return internal_getMetricsV1(impl, metrics, count);
+}
+
 ConflictSet::ConflictSet(int64_t oldestVersion)
     : impl(internal_create(oldestVersion)) {}
 
@@ -3447,6 +3561,7 @@ static_assert(std::is_standard_layout_v<ConflictSet::Result>);
 static_assert(std::is_standard_layout_v<ConflictSet::Key>);
 static_assert(std::is_standard_layout_v<ConflictSet::ReadRange>);
 static_assert(std::is_standard_layout_v<ConflictSet::WriteRange>);
+static_assert(std::is_standard_layout_v<ConflictSet::MetricsV1>);
 
 namespace {