From cd11059f105cf17aa4e99a195f0eb410e78abf5c Mon Sep 17 00:00:00 2001
From: Albert Mingkun Yang <ayang@openjdk.org>
Date: Thu, 1 Feb 2024 11:00:09 +0000
Subject: [PATCH] 8325053: Serial: Move Generation::save_used_region to
 TenuredGeneration

Reviewed-by: stefank, ehelin
---
 src/hotspot/share/gc/serial/genMarkSweep.cpp      | 7 +++----
 src/hotspot/share/gc/serial/generation.hpp        | 6 ------
 src/hotspot/share/gc/serial/serialHeap.cpp        | 5 -----
 src/hotspot/share/gc/serial/serialHeap.hpp        | 3 ---
 src/hotspot/share/gc/serial/tenuredGeneration.hpp | 6 ++++--
 5 files changed, 7 insertions(+), 20 deletions(-)

diff --git a/src/hotspot/share/gc/serial/genMarkSweep.cpp b/src/hotspot/share/gc/serial/genMarkSweep.cpp
index 28ba4615f73..41bd49edaf6 100644
--- a/src/hotspot/share/gc/serial/genMarkSweep.cpp
+++ b/src/hotspot/share/gc/serial/genMarkSweep.cpp
@@ -441,10 +441,9 @@ void GenMarkSweep::invoke_at_safepoint(bool clear_all_softrefs) {
   // Increment the invocation count
   _total_invocations++;
 
-  // Capture used regions for each generation that will be
-  // subject to collection, so that card table adjustments can
-  // be made intelligently (see clear / invalidate further below).
-  gch->save_used_regions();
+  // Capture used regions for old-gen to reestablish old-to-young invariant
+  // after full-gc.
+  gch->old_gen()->save_used_region();
 
   allocate_stacks();
 
diff --git a/src/hotspot/share/gc/serial/generation.hpp b/src/hotspot/share/gc/serial/generation.hpp
index 265b1e1ea40..5af6e5dea89 100644
--- a/src/hotspot/share/gc/serial/generation.hpp
+++ b/src/hotspot/share/gc/serial/generation.hpp
@@ -58,9 +58,6 @@ class GCStats;
 class Generation: public CHeapObj<mtGC> {
   friend class VMStructs;
  private:
-  MemRegion _prev_used_region; // for collectors that want to "remember" a value for
-                               // used region at some specific point during collection.
-
   GCMemoryManager* _gc_manager;
 
  protected:
@@ -120,9 +117,6 @@ class Generation: public CHeapObj<mtGC> {
   // generation.
   virtual MemRegion used_region() const { return _reserved; }
 
-  MemRegion prev_used_region() const { return _prev_used_region; }
-  virtual void  save_used_region()   { _prev_used_region = used_region(); }
-
   /* Returns "TRUE" iff "p" points into the reserved area of the generation. */
   bool is_in_reserved(const void* p) const {
     return _reserved.contains(p);
diff --git a/src/hotspot/share/gc/serial/serialHeap.cpp b/src/hotspot/share/gc/serial/serialHeap.cpp
index a781c950aa9..4d1ad497b85 100644
--- a/src/hotspot/share/gc/serial/serialHeap.cpp
+++ b/src/hotspot/share/gc/serial/serialHeap.cpp
@@ -294,11 +294,6 @@ size_t SerialHeap::used() const {
   return _young_gen->used() + _old_gen->used();
 }
 
-void SerialHeap::save_used_regions() {
-  _old_gen->save_used_region();
-  _young_gen->save_used_region();
-}
-
 size_t SerialHeap::max_capacity() const {
   return _young_gen->max_capacity() + _old_gen->max_capacity();
 }
diff --git a/src/hotspot/share/gc/serial/serialHeap.hpp b/src/hotspot/share/gc/serial/serialHeap.hpp
index d809ca1454b..c9a2d5ca81a 100644
--- a/src/hotspot/share/gc/serial/serialHeap.hpp
+++ b/src/hotspot/share/gc/serial/serialHeap.hpp
@@ -162,9 +162,6 @@ public:
   size_t capacity() const override;
   size_t used() const override;
 
-  // Save the "used_region" for both generations.
-  void save_used_regions();
-
   size_t max_capacity() const override;
 
   HeapWord* mem_allocate(size_t size, bool*  gc_overhead_limit_was_exceeded) override;
diff --git a/src/hotspot/share/gc/serial/tenuredGeneration.hpp b/src/hotspot/share/gc/serial/tenuredGeneration.hpp
index 329e531c1f3..6ae34a4e674 100644
--- a/src/hotspot/share/gc/serial/tenuredGeneration.hpp
+++ b/src/hotspot/share/gc/serial/tenuredGeneration.hpp
@@ -45,7 +45,7 @@ class TenuredGeneration: public Generation {
   // Abstractly, this is a subtype that gets access to protected fields.
   friend class VM_PopulateDumpSharedSpace;
 
- protected:
+  MemRegion _prev_used_region;
 
   // This is shared with other generations.
   CardTableRS* _rs;
@@ -70,7 +70,6 @@ class TenuredGeneration: public Generation {
   GenerationCounters* _gen_counters;
   CSpaceCounters*     _space_counters;
 
-
   // Attempt to expand the generation by "bytes".  Expand by at a
   // minimum "expand_bytes".  Return true if some amount (not
   // necessarily the full "bytes") was done.
@@ -95,6 +94,9 @@ class TenuredGeneration: public Generation {
   size_t free() const;
   MemRegion used_region() const;
 
+  MemRegion prev_used_region() const { return _prev_used_region; }
+  void save_used_region()   { _prev_used_region = used_region(); }
+
   void space_iterate(SpaceClosure* blk, bool usedOnly = false);
 
   void younger_refs_iterate(OopIterateClosure* blk);