Heap snapshot

base/gcutils.jl

@@ -105,6 +105,23 @@ Control whether garbage collection is enabled using a boolean argument (`true` f
 """
 enable(on::Bool) = ccall(:jl_gc_enable, Int32, (Int32,), on) != 0
 
+"""
+    GC.take_heap_snapshot(io::IOStream)
+    GC.take_heap_snapshot(filepath::String)
+
+Write a snapshot of the heap, in the JSON format expected by the Chrome
+Devtools Heap Snapshot viewer (.heapsnapshot extension), to the given
+IO stream.
+"""
+function take_heap_snapshot(io)
+    ccall(:jl_gc_take_heap_snapshot, Cvoid, (Ptr{Cvoid},), (io::IOStream).handle::Ptr{Cvoid})
+end
+function take_heap_snapshot(filepath::String)
+    open(filepath, "w") do io
+        take_heap_snapshot(io)
+    end
+end
+
 """
     GC.enable_finalizers(on::Bool)
 

src/Makefile

@@ -45,8 +45,9 @@ RUNTIME_SRCS := \
 	jltypes gf typemap smallintset ast builtins module interpreter symbol \
 	dlload sys init task array dump staticdata toplevel jl_uv datatype \
 	simplevector runtime_intrinsics precompile \
-	threading partr stackwalk gc gc-debug gc-pages gc-stacks gc-alloc-profiler method \
-	jlapi signal-handling safepoint timing subtype \
+	threading partr stackwalk \
+  gc gc-debug gc-heap-snapshot gc-alloc-profiler gc-pages gc-stacks \
+  method jlapi signal-handling safepoint timing subtype \
 	crc32c APInt-C processor ircode opaque_closure codegen-stubs coverage
 SRCS := jloptions runtime_ccall rtutils
 ifeq ($(OS),WINNT)
@@ -289,7 +290,7 @@ $(BUILDDIR)/disasm.o $(BUILDDIR)/disasm.dbg.obj: $(SRCDIR)/debuginfo.h $(SRCDIR)
 $(BUILDDIR)/dump.o $(BUILDDIR)/dump.dbg.obj: $(addprefix $(SRCDIR)/,common_symbols1.inc common_symbols2.inc builtin_proto.h serialize.h)
 $(BUILDDIR)/gc-debug.o $(BUILDDIR)/gc-debug.dbg.obj: $(SRCDIR)/gc.h
 $(BUILDDIR)/gc-pages.o $(BUILDDIR)/gc-pages.dbg.obj: $(SRCDIR)/gc.h
-$(BUILDDIR)/gc.o $(BUILDDIR)/gc.dbg.obj: $(SRCDIR)/gc.h $(SRCDIR)/gc-alloc-profiler.h
+$(BUILDDIR)/gc.o $(BUILDDIR)/gc.dbg.obj: $(SRCDIR)/gc.h $(SRCDIR)/gc-heap-snapshot.h $(SRCDIR)/gc-alloc-profiler.h
 $(BUILDDIR)/init.o $(BUILDDIR)/init.dbg.obj: $(SRCDIR)/builtin_proto.h
 $(BUILDDIR)/interpreter.o $(BUILDDIR)/interpreter.dbg.obj: $(SRCDIR)/builtin_proto.h
 $(BUILDDIR)/jitlayers.o $(BUILDDIR)/jitlayers.dbg.obj: $(SRCDIR)/jitlayers.h $(SRCDIR)/codegen_shared.h

src/gc-debug.c

@@ -1205,10 +1205,10 @@ void gc_count_pool(void)
     jl_safe_printf("************************\n");
 }
 
-int gc_slot_to_fieldidx(void *obj, void *slot)
+int gc_slot_to_fieldidx(void *obj, void *slot) JL_NOTSAFEPOINT
 {
     jl_datatype_t *vt = (jl_datatype_t*)jl_typeof(obj);
-    int nf = (int)jl_datatype_nfields(vt);
+    int nf = (int)jl_datatype_nfields(vt); // what happens if you're inlined? lol
     for (int i = 0; i < nf; i++) {
         void *fieldaddr = (char*)obj + jl_field_offset(vt, i);
         if (fieldaddr >= slot) {
@@ -1218,7 +1218,7 @@ int gc_slot_to_fieldidx(void *obj, void *slot)
     return -1;
 }
 
-int gc_slot_to_arrayidx(void *obj, void *_slot)
+int gc_slot_to_arrayidx(void *obj, void *_slot) JL_NOTSAFEPOINT
 {
     char *slot = (char*)_slot;
     jl_datatype_t *vt = (jl_datatype_t*)jl_typeof(obj);