diff --git a/tcmalloc/huge_page_filler.h b/tcmalloc/huge_page_filler.h
index 18576f258..1ff6812ef 100644
--- a/tcmalloc/huge_page_filler.h
+++ b/tcmalloc/huge_page_filler.h
@@ -887,7 +887,8 @@ class HugePageFiller {
 
   // Utility function to handle a non-hugepage backed `page_tracker` and
   // mark its unmapped pages appropriately.
-  Length HandleUnbackedHugePage(PageTracker* page_tracker, PageBitmap unbacked)
+  Length HandleUnbackedHugePage(PageTracker* page_tracker,
+                                const PageBitmap& unbacked)
       ABSL_EXCLUSIVE_LOCKS_REQUIRED(pageheap_lock);
 
  private:
@@ -1935,7 +1936,7 @@ inline void HugePageFiller<TrackerType>::OnCollapseSuccess(TrackerType* pt) {
 
 template <class TrackerType>
 inline Length HugePageFiller<TrackerType>::HandleUnbackedHugePage(
-    PageTracker* tracker, PageBitmap unbacked) {
+    PageTracker* tracker, const PageBitmap& unbacked) {
   RemoveFromFillerList(tracker);
   Length unmapped_length = tracker->MarkSubreleased(unbacked);
   subrelease_stats_.total_pages_subreleased += unmapped_length;
diff --git a/tcmalloc/huge_page_filler_fuzz.cc b/tcmalloc/huge_page_filler_fuzz.cc
index df25e8e0a..e6f46102b 100644
--- a/tcmalloc/huge_page_filler_fuzz.cc
+++ b/tcmalloc/huge_page_filler_fuzz.cc
@@ -746,7 +746,7 @@ void TreatTrackers::Perform(State& state) const {
   }
   for (PageTracker* pt : state.trackers) {
     HugePage hp = pt->location();
-    PageBitmap rel = pt->released_by_page();
+    const PageBitmap& rel = pt->released_by_page();
     for (size_t i = 0; i < kPagesPerHugePage.raw_num(); ++i) {
       PageId p = hp.first_page() + Length(i);
       if (rel.GetBit(i)) {
diff --git a/tcmalloc/huge_page_tracker.h b/tcmalloc/huge_page_tracker.h
index 85370c12f..f432bc218 100644
--- a/tcmalloc/huge_page_tracker.h
+++ b/tcmalloc/huge_page_tracker.h
@@ -209,14 +209,16 @@ class PageTracker : public TList<PageTracker>::Elem {
   Length ReleaseFree(MemoryModifyFunction& unback)
       ABSL_EXCLUSIVE_LOCKS_REQUIRED(pageheap_lock);
 
-  Length MarkSubreleased(PageBitmap unbacked)
+  Length MarkSubreleased(const PageBitmap& unbacked)
       ABSL_EXCLUSIVE_LOCKS_REQUIRED(pageheap_lock);
 
-  [[nodiscard]] PageBitmap released_by_page() const {
+  [[nodiscard]] const PageBitmap& released_by_page() const
+      ABSL_EXCLUSIVE_LOCKS_REQUIRED(pageheap_lock) {
     return released_by_page_;
   }
 
-  [[nodiscard]] PageBitmap allocated_pages_bitmap() const {
+  [[nodiscard]] const PageBitmap& allocated_pages_bitmap() const
+      ABSL_EXCLUSIVE_LOCKS_REQUIRED(pageheap_lock) {
     return free_.bits();
   }
 
@@ -326,9 +328,9 @@ class PageTracker : public TList<PageTracker>::Elem {
     size_t n_used_stale;
   };
 
-  HardwarePageResidencyInfo CountInfoInHugePage(PageBitmap unbacked,
-                                                PageBitmap swapped,
-                                                PageBitmap stale) const;
+  HardwarePageResidencyInfo CountInfoInHugePage(const PageBitmap& unbacked,
+                                                const PageBitmap& swapped,
+                                                const PageBitmap& stale) const;
 
  private:
   HugePage location_;
@@ -427,7 +429,8 @@ inline void PageTracker::SetAnonVmaName(MemoryTagFunction& set_anon_vma_name,
 }
 
 inline PageTracker::HardwarePageResidencyInfo PageTracker::CountInfoInHugePage(
-    PageBitmap unbacked, PageBitmap swapped, PageBitmap stale) const {
+    const PageBitmap& unbacked, const PageBitmap& swapped,
+    const PageBitmap& stale) const {
   // TODO(b/424551232): Add support for the scenario when native page size is
   // larger than TCMalloc page size.
   const size_t kHardwarePagesInHugePage = kHugePageSize / GetPageSize();
@@ -436,7 +439,7 @@ inline PageTracker::HardwarePageResidencyInfo PageTracker::CountInfoInHugePage(
   }
   TC_ASSERT_LE(kHardwarePagesInHugePage, kMaxResidencyBits);
 
-  const PageBitmap free = free_.bits();
+  const PageBitmap& free = free_.bits();
 
   TC_ASSERT_EQ(kHardwarePagesInHugePage % kPagesPerHugePage.raw_num(), 0);
   const int shift = kHardwarePagesInHugePage / kPagesPerHugePage.raw_num();
@@ -521,8 +524,8 @@ inline Length PageTracker::ReleaseFree(MemoryModifyFunction& unback) {
   return Length(count);
 }
 
-inline Length PageTracker::MarkSubreleased(PageBitmap unbacked) {
-  PageBitmap free = free_.bits();
+inline Length PageTracker::MarkSubreleased(const PageBitmap& unbacked) {
+  const PageBitmap& free = free_.bits();
 
   // TODO(b/525422238): The residency bitmap was captured outside of the
   // lock. So, in a rare case, it's possible that the page was allocated,
diff --git a/tcmalloc/internal/range_tracker.h b/tcmalloc/internal/range_tracker.h
index 9144e5384..c7f4be154 100644
--- a/tcmalloc/internal/range_tracker.h
+++ b/tcmalloc/internal/range_tracker.h
@@ -169,7 +169,7 @@ class RangeTracker {
 
   void Clear();
 
-  Bitmap<N> bits() const;
+  const Bitmap<N>& bits() const;
 
  private:
   Bitmap<N> bits_;
@@ -319,7 +319,7 @@ inline void RangeTracker<N>::Unmark(size_t index, size_t n) {
 }
 
 template <size_t N>
-inline Bitmap<N> RangeTracker<N>::bits() const {
+inline const Bitmap<N>& RangeTracker<N>::bits() const {
   return bits_;
 }