From 4c824edbe46ed29678a5f5c63b1fc95036b98042 Mon Sep 17 00:00:00 2001
From: Roland Conybeare <rconybeare@gmail.com>
Date: Sun, 24 Aug 2025 17:03:04 -0400
Subject: [PATCH] xo-imgui: ex2: + average efficiency + plot

---
 include/xo/alloc/GcStatistics.hpp | 44 +++++++++++++++++++++++--------
 src/alloc/GC.cpp                  | 13 ++++++++-
 2 files changed, 45 insertions(+), 12 deletions(-)

diff --git a/include/xo/alloc/GcStatistics.hpp b/include/xo/alloc/GcStatistics.hpp
index c0058b5f..b591bf22 100644
--- a/include/xo/alloc/GcStatistics.hpp
+++ b/include/xo/alloc/GcStatistics.hpp
@@ -163,17 +163,23 @@ namespace xo {
                                               std::size_t garbage0_z,
                                               std::size_t garbage1_z,
                                               std::size_t garbageN_z,
-                                              nanos dt) : gc_seq_{gc_seq},
-                                                          upto_{upto},
-                                                          new_alloc_z_{new_alloc_z},
-                                                          survive_z_{survive_z},
-                                                          promote_z_{promote_z},
-                                                          persist_z_{persist_z},
-                                                          effort_z_{effort_z},
-                                                          garbage0_z_{garbage0_z},
-                                                          garbage1_z_{garbage1_z},
-                                                          garbageN_z_{garbageN_z},
-                                                          dt_{dt} {}
+                                              nanos dt,
+                                              std::size_t sum_effort_z,
+                                              std::size_t sum_garbage_z)
+            : gc_seq_{gc_seq},
+              upto_{upto},
+              new_alloc_z_{new_alloc_z},
+              survive_z_{survive_z},
+              promote_z_{promote_z},
+              persist_z_{persist_z},
+              effort_z_{effort_z},
+              garbage0_z_{garbage0_z},
+              garbage1_z_{garbage1_z},
+              garbageN_z_{garbageN_z},
+              dt_{dt},
+              sum_effort_z_{sum_effort_z},
+              sum_garbage_z_{sum_garbage_z}
+                {}
             constexpr GcStatisticsHistoryItem(const GcStatisticsHistoryItem &) = default;
 
             std::size_t garbage_z() const { return garbage0_z_ + garbage1_z_ + garbageN_z_; }
@@ -184,6 +190,11 @@ namespace xo {
                 return gz / static_cast<float>(effort_z_ + gz);
             }
 
+            /** lifetime byte-weighted average collection efficiency.  Always in [0.0, 1.0] **/
+            float average_efficiency() const {
+                return sum_garbage_z_ / static_cast<float>(sum_effort_z_ + sum_garbage_z_);
+            }
+
             /** collection rate, in bytes/sec **/
             float collection_rate() const;
 
@@ -199,6 +210,10 @@ namespace xo {
                 garbage1_z_ = x.garbage1_z_;
                 garbageN_z_ = x.garbageN_z_;
                 this->dt_.scale_ = x.dt_.scale_;
+
+                sum_effort_z_ = x.sum_effort_z_;
+                sum_garbage_z_ = x.sum_garbage_z_;
+
                 return *this;
             }
 
@@ -229,6 +244,13 @@ namespace xo {
             std::size_t garbageN_z_ = 0;
             /** elapsed time for this GC (see @ref GC::execute_gc) **/
             nanos dt_;
+
+            // ----- cumulative statistics -----
+
+            /** sum (in bytes) copied by collections since inception **/
+            std::size_t sum_effort_z_ = 0;
+            /** sum (in bytes) of garbage collected since inception **/
+            std::size_t sum_garbage_z_ = 0;
         };
 
         inline std::ostream & operator<< (std::ostream & os, const GcStatisticsHistoryItem & x) {
diff --git a/src/alloc/GC.cpp b/src/alloc/GC.cpp
index 200ac218..1b5481cb 100644
--- a/src/alloc/GC.cpp
+++ b/src/alloc/GC.cpp
@@ -1119,6 +1119,15 @@ namespace xo {
                 // still want to update tenured stats for current alloc size
                 this->gc_statistics_.update_snapshot(generation::tenured, T_after_gc);
             }
+
+            std::size_t sum_effort_z = effort_z;
+            std::size_t sum_garbage_z = garbage0_z + garbage1_z + garbageN_z;
+
+            if (gc_history_.size() > 0) {
+                sum_effort_z += gc_history_.back().sum_effort_z_;
+                sum_garbage_z += gc_history_.back().sum_garbage_z_;
+            }
+
             GcStatisticsHistoryItem item(gc_statistics_.n_gc(),
                                          upto,
                                          new_alloc_z,
@@ -1129,7 +1138,9 @@ namespace xo {
                                          garbage0_z,
                                          garbage1_z,
                                          garbageN_z,
-                                         dt);
+                                         dt,
+                                         sum_effort_z,
+                                         sum_garbage_z);
 
             log && log(xtag("gcseq_after_gc", gc_statistics_.n_gc()),
                        xtag("item", item));