From 8c739b1bdc8621c06ac8f8b7fef65ce21be976b7 Mon Sep 17 00:00:00 2001
From: Kiran <kpamnany@users.noreply.github.com>
Date: Wed, 31 May 2023 16:16:01 -0400
Subject: [PATCH] Add GC metric `last_full_sweep` (#50018)

Records the time that the last full sweep ran.
---
 base/timing.jl | 1 +
 src/gc.c       | 3 +++
 src/gc.h       | 1 +
 3 files changed, 5 insertions(+)

diff --git a/base/timing.jl b/base/timing.jl
index 04994914049a0..691db3cbbd260 100644
--- a/base/timing.jl
+++ b/base/timing.jl
@@ -25,6 +25,7 @@ struct GC_Num
     mark_time       ::Int64
     total_sweep_time  ::Int64
     total_mark_time   ::Int64
+    last_full_sweep ::Int64
 end
 
 gc_num() = ccall(:jl_gc_num, GC_Num, ())
diff --git a/src/gc.c b/src/gc.c
index 4983570054c55..0f30e8305b78c 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -3283,6 +3283,9 @@ static int _jl_gc_collect(jl_ptls_t ptls, jl_gc_collection_t collection)
     uint64_t sweep_time = gc_end_time - start_sweep_time;
     gc_num.total_sweep_time += sweep_time;
     gc_num.sweep_time = sweep_time;
+    if (sweep_full) {
+        gc_num.last_full_sweep = gc_end_time;
+    }
 
     // sweeping is over
     // 6. if it is a quick sweep, put back the remembered objects in queued state
diff --git a/src/gc.h b/src/gc.h
index 7d6aff3499eae..8436a653dc32b 100644
--- a/src/gc.h
+++ b/src/gc.h
@@ -82,6 +82,7 @@ typedef struct {
     uint64_t    mark_time;
     uint64_t    total_sweep_time;
     uint64_t    total_mark_time;
+    uint64_t    last_full_sweep;
 } jl_gc_num_t;
 
 enum {