8220594: ZGC: Remove superfluous ZPage::is_active()

Reviewed-by: stefank, eosterlund

src/hotspot/share/gc/z/zPage.cpp

@@ -25,13 +25,11 @@
 #include "gc/z/zPage.inline.hpp"
 #include "gc/z/zPhysicalMemory.inline.hpp"
 #include "gc/z/zVirtualMemory.inline.hpp"
-#include "runtime/orderAccess.hpp"
 #include "utilities/align.hpp"
 #include "utilities/debug.hpp"
 
 ZPage::ZPage(uint8_t type, ZVirtualMemory vmem, ZPhysicalMemory pmem) :
     _type(type),
-    _active(0),
     _numa_id((uint8_t)-1),
     _seqnum(0),
     _virtual(vmem),
@@ -47,30 +45,20 @@ ZPage::ZPage(uint8_t type, ZVirtualMemory vmem, ZPhysicalMemory pmem) :
 }
 
 ZPage::~ZPage() {
-  assert(!is_active(), "Should not be active");
-  assert(_physical.is_null(), "Should be detached");
+  assert(_physical.is_null(), "Should be null");
 }
 
 void ZPage::reset() {
-  assert(!is_active(), "Should not be active");
-
   _seqnum = ZGlobalSeqNum;
   _top = start();
   _livemap.reset();
-
-  // Make sure we don't make the page active before
-  // the reset of the above fields are visible.
-  OrderAccess::storestore();
-
-  _active = 1;
 }
 
 void ZPage::print_on(outputStream* out) const {
-  out->print_cr(" %-6s  " PTR_FORMAT " " PTR_FORMAT " " PTR_FORMAT " %s%s%s",
+  out->print_cr(" %-6s  " PTR_FORMAT " " PTR_FORMAT " " PTR_FORMAT " %s%s",
                 type_to_string(), start(), top(), end(),
                 is_allocating()  ? " Allocating"  : "",
-                is_relocatable() ? " Relocatable" : "",
-                !is_active()     ? " Inactive"    : "");
+                is_relocatable() ? " Relocatable" : "");
 }
 
 void ZPage::print() const {

src/hotspot/share/gc/z/zPage.hpp

@@ -37,7 +37,6 @@ class ZPage : public CHeapObj<mtGC> {
 private:
   // Always hot
   const uint8_t        _type;             // Page type
-  volatile uint8_t     _active;           // Active flag
   uint8_t              _numa_id;          // NUMA node affinity
   uint32_t             _seqnum;           // Allocation sequence number
   const ZVirtualMemory _virtual;          // Virtual start/end address
@@ -80,9 +79,6 @@ public:
   uintptr_t block_start(uintptr_t addr) const;
   bool block_is_obj(uintptr_t addr) const;
 
-  bool is_active() const;
-  void set_inactive();
-
   bool is_allocating() const;
   bool is_relocatable() const;
 

src/hotspot/share/gc/z/zPage.inline.hpp

@@ -149,20 +149,12 @@ inline bool ZPage::block_is_obj(uintptr_t addr) const {
   return ZAddress::offset(addr) < top();
 }
 
-inline bool ZPage::is_active() const {
-  return OrderAccess::load_acquire(&_active) != 0;
-}
-
-inline void ZPage::set_inactive() {
-  OrderAccess::release_store(&_active, (uint8_t)0);
-}
-
 inline bool ZPage::is_allocating() const {
-  return is_active() && _seqnum == ZGlobalSeqNum;
+  return _seqnum == ZGlobalSeqNum;
 }
 
 inline bool ZPage::is_relocatable() const {
-  return is_active() && _seqnum < ZGlobalSeqNum;
+  return _seqnum < ZGlobalSeqNum;
 }
 
 inline bool ZPage::is_mapped() const {

src/hotspot/share/gc/z/zPageAllocator.cpp

@@ -470,9 +470,6 @@ void ZPageAllocator::free_page(ZPage* page, bool reclaimed) {
   // Update used statistics
   decrease_used(page->size(), reclaimed);
 
-  // Make page inactive
-  page->set_inactive();
-
   // Cache page
   _cache.free_page(page);
 

src/hotspot/share/gc/z/zPageCache.cpp

@@ -118,8 +118,6 @@ ZPage* ZPageCache::alloc_page(uint8_t type, size_t size) {
 }
 
 void ZPageCache::free_page(ZPage* page) {
-  assert(!page->is_active(), "Invalid page state");
-
   const uint8_t type = page->type();
   if (type == ZPageTypeSmall) {
     _small.get(page->numa_id()).insert_first(page);

test/hotspot/gtest/gc/z/test_zForwarding.cpp

@@ -174,7 +174,6 @@ public:
 
     // Teardown page
     page.physical_memory().clear();
-    page.set_inactive();
   }
 
   // Run the given function with a few different input values.