[heap] Remove page_start_ from SlotSet

Do not store page_start_ in SlotSet anymore, when needed this address
can be calculated cheaply and be passed in from the caller.

Bug: v8:9454
Change-Id: I4cdb010e4126680d8df500e40ae3d0bc884cf501
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1838731Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#64103}

src/heap/remembered-set.h

@@ -36,7 +36,8 @@ class RememberedSetOperations {
     if (slots != nullptr) {
       size_t pages = (chunk->size() + Page::kPageSize - 1) / Page::kPageSize;
       for (size_t page = 0; page < pages; page++) {
-        slots[page].Iterate(callback, mode);
+        slots[page].Iterate(chunk->address() + page * Page::kPageSize, callback,
+                            mode);
       }
     }
   }

src/heap/slot-set.h

@@ -22,8 +22,7 @@ namespace internal {
 enum SlotCallbackResult { KEEP_SLOT, REMOVE_SLOT };
 
 // Data structure for maintaining a set of slots in a standard (non-large)
-// page. The base address of the page must be set with SetPageStart before any
-// operation.
+// page.
 // The data structure assumes that the slots are pointer size aligned and
 // splits the valid slot offset range into kBuckets buckets.
 // Each bucket is a bitmap with a bit corresponding to a single slot offset.
@@ -50,8 +49,6 @@ class SlotSet : public Malloced {
     FreeToBeFreedBuckets();
   }
 
-  void SetPageStart(Address page_start) { page_start_ = page_start; }
-
   // The slot offset specifies a slot at address page_start_ + slot_offset.
   // AccessMode defines whether there can be concurrent access on the buckets
   // or not.
@@ -190,7 +187,7 @@ class SlotSet : public Malloced {
   //    else return REMOVE_SLOT;
   // });
   template <typename Callback>
-  int Iterate(Callback callback, EmptyBucketMode mode) {
+  int Iterate(Address page_start, Callback callback, EmptyBucketMode mode) {
     int new_count = 0;
     for (int bucket_index = 0; bucket_index < kBuckets; bucket_index++) {
       Bucket bucket = LoadBucket(&buckets_[bucket_index]);
@@ -206,7 +203,7 @@ class SlotSet : public Malloced {
               int bit_offset = base::bits::CountTrailingZeros(cell);
               uint32_t bit_mask = 1u << bit_offset;
               uint32_t slot = (cell_offset + bit_offset) << kTaggedSizeLog2;
-              if (callback(MaybeObjectSlot(page_start_ + slot)) == KEEP_SLOT) {
+              if (callback(MaybeObjectSlot(page_start + slot)) == KEEP_SLOT) {
                 ++in_bucket_count;
               } else {
                 mask |= bit_mask;
@@ -382,7 +379,6 @@ class SlotSet : public Malloced {
   }
 
   Bucket buckets_[kBuckets];
-  Address page_start_;
   base::Mutex to_be_freed_buckets_mutex_;
   std::stack<uint32_t*> to_be_freed_buckets_;
 };

src/heap/spaces.cc

@@ -1430,11 +1430,7 @@ void MemoryChunk::ReleaseAllAllocatedMemory() {
 static SlotSet* AllocateAndInitializeSlotSet(size_t size, Address page_start) {
   size_t pages = (size + Page::kPageSize - 1) / Page::kPageSize;
   DCHECK_LT(0, pages);
-  SlotSet* slot_set = new SlotSet[pages];
-  for (size_t i = 0; i < pages; i++) {
-    slot_set[i].SetPageStart(page_start + i * Page::kPageSize);
-  }
-  return slot_set;
+  return new SlotSet[pages];
 }
 
 template V8_EXPORT_PRIVATE SlotSet* MemoryChunk::AllocateSlotSet<OLD_TO_NEW>();

test/unittests/heap/slot-set-unittest.cc

@@ -16,7 +16,6 @@ namespace internal {
 
 TEST(SlotSet, InsertAndLookup1) {
   SlotSet set;
-  set.SetPageStart(0);
   for (int i = 0; i < Page::kPageSize; i += kTaggedSize) {
     EXPECT_FALSE(set.Lookup(i));
   }
@@ -30,7 +29,6 @@ TEST(SlotSet, InsertAndLookup1) {
 
 TEST(SlotSet, InsertAndLookup2) {
   SlotSet set;
-  set.SetPageStart(0);
   for (int i = 0; i < Page::kPageSize; i += kTaggedSize) {
     if (i % 7 == 0) {
       set.Insert<AccessMode::ATOMIC>(i);
@@ -47,7 +45,6 @@ TEST(SlotSet, InsertAndLookup2) {
 
 TEST(SlotSet, Iterate) {
   SlotSet set;
-  set.SetPageStart(0);
   for (int i = 0; i < Page::kPageSize; i += kTaggedSize) {
     if (i % 7 == 0) {
       set.Insert<AccessMode::ATOMIC>(i);
@@ -55,6 +52,7 @@ TEST(SlotSet, Iterate) {
   }
 
   set.Iterate(
+      kNullAddress,
       [](MaybeObjectSlot slot) {
         if (slot.address() % 3 == 0) {
           return KEEP_SLOT;
@@ -75,7 +73,6 @@ TEST(SlotSet, Iterate) {
 
 TEST(SlotSet, Remove) {
   SlotSet set;
-  set.SetPageStart(0);
   for (int i = 0; i < Page::kPageSize; i += kTaggedSize) {
     if (i % 7 == 0) {
       set.Insert<AccessMode::ATOMIC>(i);
@@ -99,7 +96,6 @@ TEST(SlotSet, Remove) {
 
 void CheckRemoveRangeOn(uint32_t start, uint32_t end) {
   SlotSet set;
-  set.SetPageStart(0);
   uint32_t first = start == 0 ? 0 : start - kTaggedSize;
   uint32_t last = end == Page::kPageSize ? end - kTaggedSize : end;
   for (const auto mode :
@@ -137,7 +133,6 @@ TEST(SlotSet, RemoveRange) {
     }
   }
   SlotSet set;
-  set.SetPageStart(0);
   for (const auto mode :
        {SlotSet::FREE_EMPTY_BUCKETS, SlotSet::KEEP_EMPTY_BUCKETS}) {
     set.Insert<AccessMode::ATOMIC>(Page::kPageSize / 2);