From 6f43328c953e50be924d16b41e35255f694d8794 Mon Sep 17 00:00:00 2001
Date: Mon, 6 Apr 2020 18:13:30 +0000
Subject: [PATCH] leaf optimize in ParallelScanvageGC

Summary: <leaf gc optimization>: <1. add _is_gc_leaf field in klass, if none of klass field is reference,then this klass's oop is leaf, set this at classfile parser.2. ParallelScanvage copy before push_depth if oop is leaf.3. leaf oop don't push_contents.>
LLT: <jtreg>
Bug url: <N/A>
---
 src/hotspot/share/classfile/classFileParser.cpp          |  7 ++++++-
 .../share/gc/parallel/psPromotionManager.inline.hpp      | 16 ++++++++++++----
 src/hotspot/share/oops/klass.cpp                         |  2 ++
 src/hotspot/share/oops/klass.hpp                         |  5 +++++
 4 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/src/hotspot/share/classfile/classFileParser.cpp b/src/hotspot/share/classfile/classFileParser.cpp
index bf8ac6f3b..99f99309d 100644
--- a/src/hotspot/share/classfile/classFileParser.cpp
+++ b/src/hotspot/share/classfile/classFileParser.cpp
@@ -4363,7 +4363,7 @@ void ClassFileParser::layout_fields(ConstantPool* cp,
   info->has_nonstatic_fields = has_nonstatic_fields;
 }
 
-static void fill_oop_maps(const InstanceKlass* k,
+static void fill_oop_maps(InstanceKlass* k,
                           unsigned int nonstatic_oop_map_count,
                           const int* nonstatic_oop_offsets,
                           const unsigned int* nonstatic_oop_counts) {
@@ -4373,6 +4373,11 @@ static void fill_oop_maps(const InstanceKlass* k,
   OopMapBlock* this_oop_map = k->start_of_nonstatic_oop_maps();
   const InstanceKlass* const super = k->superklass();
   const unsigned int super_count = super ? super->nonstatic_oop_map_count() : 0;
+
+  const bool super_is_gc_leaf = super ? super->oop_is_gc_leaf() : true;
+  bool this_is_gc_leaf = super_is_gc_leaf && (nonstatic_oop_map_count == 0);
+  k->set_oop_is_gc_leaf(this_is_gc_leaf);
+
   if (super_count > 0) {
     // Copy maps from superklass
     OopMapBlock* super_oop_map = super->start_of_nonstatic_oop_maps();
diff --git a/src/hotspot/share/gc/parallel/psPromotionManager.inline.hpp b/src/hotspot/share/gc/parallel/psPromotionManager.inline.hpp
index 1ef900783..07f736cf2 100644
--- a/src/hotspot/share/gc/parallel/psPromotionManager.inline.hpp
+++ b/src/hotspot/share/gc/parallel/psPromotionManager.inline.hpp
@@ -59,7 +59,12 @@ inline void PSPromotionManager::claim_or_forward_internal_depth(T* p) {
       }
       RawAccess<IS_NOT_NULL>::oop_store(p, o);
     } else {
-      push_depth(p);
+      //leaf object copy in advanced, reduce cost of push and pop
+      if (!o->klass()->oop_is_gc_leaf()) {
+        push_depth(p);
+      } else {
+        copy_and_push_safe_barrier<T, false>(p);
+      }
     }
   }
 }
@@ -214,7 +219,7 @@ inline oop PSPromotionManager::copy_to_survivor_space(oop o) {
 
     // Now we have to CAS in the header.
     // Make copy visible to threads reading the forwardee.
-    if (o->cas_forward_to(new_obj, test_mark, memory_order_release)) {
+    if (o->cas_forward_to(new_obj, test_mark, o->klass()->oop_is_gc_leaf()? memory_order_relaxed : memory_order_release)) {
       // We won any races, we "own" this object.
       assert(new_obj == o->forwardee(), "Sanity");
 
@@ -238,8 +243,11 @@ inline oop PSPromotionManager::copy_to_survivor_space(oop o) {
         push_depth(masked_o);
         TASKQUEUE_STATS_ONLY(++_arrays_chunked; ++_masked_pushes);
       } else {
-        // we'll just push its contents
-        push_contents(new_obj);
+        //leaf object don't have contents, never need push_contents
+        if (!o->klass()->oop_is_gc_leaf()) {
+          // we'll just push its contents
+          push_contents(new_obj);
+        }
       }
     }  else {
       // We lost, someone else "owns" this object
diff --git a/src/hotspot/share/oops/klass.cpp b/src/hotspot/share/oops/klass.cpp
index 01c5ed5bd..180ba8f41 100644
--- a/src/hotspot/share/oops/klass.cpp
+++ b/src/hotspot/share/oops/klass.cpp
@@ -202,6 +202,8 @@ Klass::Klass(KlassID id) : _id(id),
   CDS_JAVA_HEAP_ONLY(_archived_mirror = 0;)
   _primary_supers[0] = this;
   set_super_check_offset(in_bytes(primary_supers_offset()));
+
+  set_oop_is_gc_leaf(false);
 }
 
 jint Klass::array_layout_helper(BasicType etype) {
diff --git a/src/hotspot/share/oops/klass.hpp b/src/hotspot/share/oops/klass.hpp
index b77a19deb..a624586aa 100644
--- a/src/hotspot/share/oops/klass.hpp
+++ b/src/hotspot/share/oops/klass.hpp
@@ -165,6 +165,8 @@ class Klass : public Metadata {
   // vtable length
   int _vtable_len;
 
+  bool _is_gc_leaf;
+
 private:
   // This is an index into FileMapHeader::_shared_path_table[], to
   // associate this class with the JAR file where it's loaded from during
@@ -603,6 +605,9 @@ protected:
                                                     is_typeArray_klass_slow()); }
   #undef assert_same_query
 
+  void set_oop_is_gc_leaf(bool is_gc_leaf)        { _is_gc_leaf = is_gc_leaf; }
+  inline bool oop_is_gc_leaf()              const { return _is_gc_leaf; }
+
   // Access flags
   AccessFlags access_flags() const         { return _access_flags;  }
   void set_access_flags(AccessFlags flags) { _access_flags = flags; }
-- 
1.8.3.1