add function to get total live bytes (#33094)

Author: JeffBezanson

base/util.jl

@@ -60,6 +60,19 @@ end
 # total time spend in garbage collection, in nanoseconds
 gc_time_ns() = ccall(:jl_gc_total_hrtime, UInt64, ())
 
+"""
+    Base.gc_live_bytes()
+
+Return the total size (in bytes) of objects currently in memory.
+This is computed as the total size of live objects after
+the last garbage collection, plus the number of bytes allocated
+since then.
+"""
+function gc_live_bytes()
+    num = gc_num()
+    Int(ccall(:jl_gc_live_bytes, Int64, ())) + num.allocd + num.deferred_alloc
+end
+
 # print elapsed time, return expression value
 const _mem_units = ["byte", "KiB", "MiB", "GiB", "TiB", "PiB"]
 const _cnt_units = ["", " k", " M", " G", " T", " P"]

src/gc.c

@@ -2655,6 +2655,11 @@ void jl_gc_sync_total_bytes(void)
     jl_gc_get_total_bytes(&last_gc_total_bytes);
 }
 
+JL_DLLEXPORT int64_t jl_gc_live_bytes(void)
+{
+    return live_bytes;
+}
+
 static void jl_gc_premark(jl_ptls_t ptls2)
 {
     arraylist_t *remset = ptls2->heap.remset;