Add write time stats to celldb/db_stats.txt (#972)

Co-authored-by: SpyCheese <mikle98@yandex.ru>

validator/db/db-utils.cpp

@@ -0,0 +1,54 @@
+/*
+    This file is part of TON Blockchain Library.
+
+    TON Blockchain Library is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation, either version 2 of the License, or
+    (at your option) any later version.
+
+    TON Blockchain Library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with TON Blockchain Library.  If not, see <http://www.gnu.org/licenses/>.
+*/
+#include "db-utils.h"
+
+#include "td/utils/logging.h"
+
+#include <cmath>
+
+namespace ton::validator {
+
+void PercentileStats::insert(double value) {
+  values_.insert(value);
+}
+
+std::string PercentileStats::to_string() const {
+  double percentiles[4] = {0.0, 0.0, 0.0, 0.0};
+  double sum = 0.0;
+  size_t size = values_.size();
+  if (!values_.empty()) {
+    size_t indices[4] = {(size_t)std::ceil(0.5 * (double)size) - 1, (size_t)std::ceil(0.95 * (double)size) - 1,
+                         (size_t)std::ceil(0.99 * (double)size) - 1, size - 1};
+    size_t i = 0;
+    for (auto it = values_.begin(); it != values_.end(); ++it, ++i) {
+      for (size_t j = 0; j < 4; ++j) {
+        if (indices[j] == i) {
+          percentiles[j] = *it;
+        }
+      }
+      sum += *it;
+    }
+  }
+  return PSTRING() << "P50 : " << percentiles[0] << " P95 : " << percentiles[1] << " P99 : " << percentiles[2]
+                   << " P100 : " << percentiles[3] << " COUNT : " << size << " SUM : " << sum;
+}
+
+void PercentileStats::clear() {
+  values_.clear();
+}
+
+}  // namespace ton::validator