From 0a19c8b043a07a435f33a4d7b3c0bf904f354fe1 Mon Sep 17 00:00:00 2001
From: Roland Conybeare <rconybeare@gmail.com>
Date: Sat, 23 Aug 2025 13:09:59 -0400
Subject: [PATCH] xo-alloc: track GC efficiency

---
 include/xo/alloc/GcStatistics.hpp | 11 +++++++++++
 src/alloc/GcStatistics.cpp        | 17 +++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/include/xo/alloc/GcStatistics.hpp b/include/xo/alloc/GcStatistics.hpp
index d0f54084..c0058b5f 100644
--- a/include/xo/alloc/GcStatistics.hpp
+++ b/include/xo/alloc/GcStatistics.hpp
@@ -176,6 +176,17 @@ namespace xo {
                                                           dt_{dt} {}
             constexpr GcStatisticsHistoryItem(const GcStatisticsHistoryItem &) = default;
 
+            std::size_t garbage_z() const { return garbage0_z_ + garbage1_z_ + garbageN_z_; }
+
+            float efficiency() const {
+                std::size_t gz = this->garbage_z();
+
+                return gz / static_cast<float>(effort_z_ + gz);
+            }
+
+            /** collection rate, in bytes/sec **/
+            float collection_rate() const;
+
             GcStatisticsHistoryItem & operator=(const GcStatisticsHistoryItem & x) {
                 gc_seq_ = x.gc_seq_;
                 upto_ = x.upto_;
diff --git a/src/alloc/GcStatistics.cpp b/src/alloc/GcStatistics.cpp
index 72624403..deb30685 100644
--- a/src/alloc/GcStatistics.cpp
+++ b/src/alloc/GcStatistics.cpp
@@ -103,6 +103,23 @@ namespace xo {
                << ">";
         }
 
+        float
+        GcStatisticsHistoryItem::collection_rate() const {
+            using namespace xo::qty::qty;
+
+            float gz = this->garbage_z();
+
+            auto dt_nanos = this->dt_.with_repr<float>();
+            auto dt_sec = dt_nanos.rescale_ext<xo::qty::u::second>();
+            auto rate = gz / dt_sec;
+            float retval = rate.scale();
+
+            //scope log(XO_DEBUG(true));
+            //log && log(xtag("gz", gz), xtag("dt_sec", dt_sec), xtag("rate", rate), xtag("rate/sec", retval));
+
+            return retval;
+        }
+
         void
         GcStatisticsHistoryItem::display(std::ostream & os) const
         {