From 726ef0e9142236d2c04f941d35178ab183e0d713 Mon Sep 17 00:00:00 2001
From: Diogo Netto <61364108+d-netto@users.noreply.github.com>
Date: Wed, 6 Dec 2023 09:57:44 -0300
Subject: [PATCH] functionality to expose page utilization at the julia level
 (#113)

---
 base/timing.jl | 7 +++++++
 src/gc.c       | 8 ++------
 src/gc.h       | 3 ---
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/base/timing.jl b/base/timing.jl
index aeca790bce7e9..4b14161aa89d2 100644
--- a/base/timing.jl
+++ b/base/timing.jl
@@ -98,6 +98,13 @@ function gc_live_bytes()
     Int(ccall(:jl_gc_live_bytes, Int64, ())) + num.allocd + num.deferred_alloc
 end
 
+# must be kept in sync with the value from `src/julia_threads.h``
+const JL_GC_N_MAX_POOLS = 51
+function gc_page_utilization_data()
+    page_utilization_raw = cglobal(:jl_gc_page_utilization_stats, Float64)
+    return Base.unsafe_wrap(Array, page_utilization_raw, JL_GC_N_MAX_POOLS, own=false)
+end
+
 """
     Base.jit_total_bytes()
 
diff --git a/src/gc.c b/src/gc.c
index 4003e61accf6a..832e06adfded1 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -1391,21 +1391,19 @@ int jl_gc_classify_pools(size_t sz, int *osize)
 // sweep phase
 
 gc_fragmentation_stat_t gc_page_fragmentation_stats[JL_GC_N_POOLS];
+JL_DLLEXPORT double jl_gc_page_utilization_stats[JL_GC_N_MAX_POOLS];
 
 extern gc_fragmentation_stat_t gc_page_fragmentation_stats[JL_GC_N_POOLS];
 
 STATIC_INLINE void gc_update_page_fragmentation_data(jl_gc_pagemeta_t *pg) JL_NOTSAFEPOINT
 {
-#ifdef GC_MEASURE_PAGE_FRAGMENTATION
     gc_fragmentation_stat_t *stats = &gc_page_fragmentation_stats[pg->pool_n];
     jl_atomic_fetch_add(&stats->n_freed_objs, pg->nfree);
     jl_atomic_fetch_add(&stats->n_pages_allocd, 1);
-#endif
 }
 
 STATIC_INLINE void gc_dump_page_utilization_data(void) JL_NOTSAFEPOINT
 {
-#ifdef GC_MEASURE_PAGE_FRAGMENTATION
     for (int i = 0; i < JL_GC_N_POOLS; i++) {
         gc_fragmentation_stat_t *stats = &gc_page_fragmentation_stats[i];
         double utilization = 1.0;
@@ -1414,12 +1412,10 @@ STATIC_INLINE void gc_dump_page_utilization_data(void) JL_NOTSAFEPOINT
         if (n_pages_allocd != 0) {
             utilization -= ((double)n_freed_objs * (double)jl_gc_sizeclasses[i]) / (double)n_pages_allocd / (double)GC_PAGE_SZ;
         }
-        jl_safe_printf("Size class %d: %.2f%% utilization\n", jl_gc_sizeclasses[i], utilization * 100.0);
+        jl_gc_page_utilization_stats[i] = utilization;
         jl_atomic_store_relaxed(&stats->n_freed_objs, 0);
         jl_atomic_store_relaxed(&stats->n_pages_allocd, 0);
     }
-    jl_safe_printf("-----------------------------------------\n");
-#endif
 }
 
 int64_t buffered_pages = 0;
diff --git a/src/gc.h b/src/gc.h
index e22cfe4c13e90..a6ad9f41dabf0 100644
--- a/src/gc.h
+++ b/src/gc.h
@@ -223,9 +223,6 @@ STATIC_INLINE jl_gc_pagemeta_t *pop_lf_back(jl_gc_page_stack_t *pool) JL_NOTSAFE
     }
 }
 
-// data structures for tracking fragmentation in the pool allocator
-// #define GC_MEASURE_PAGE_FRAGMENTATION
-
 typedef struct {
     _Atomic(size_t) n_freed_objs;
     _Atomic(size_t) n_pages_allocd;