diff --git a/compiler-rt/lib/tsan/rtl/tsan_clock.h b/compiler-rt/lib/tsan/rtl/tsan_clock.h
--- a/compiler-rt/lib/tsan/rtl/tsan_clock.h
+++ b/compiler-rt/lib/tsan/rtl/tsan_clock.h
@@ -17,7 +17,7 @@
 
 namespace __tsan {
 
-typedef DenseSlabAlloc<ClockBlock, 1<<16, 1<<10> ClockAlloc;
+typedef DenseSlabAlloc<ClockBlock, 1 << 22, 1 << 10> ClockAlloc;
 typedef DenseSlabAllocCache ClockCache;
 
 // The clock that lives in sync variables (mutexes, atomics, etc).
diff --git a/compiler-rt/lib/tsan/rtl/tsan_dense_alloc.h b/compiler-rt/lib/tsan/rtl/tsan_dense_alloc.h
--- a/compiler-rt/lib/tsan/rtl/tsan_dense_alloc.h
+++ b/compiler-rt/lib/tsan/rtl/tsan_dense_alloc.h
@@ -29,28 +29,40 @@
   typedef u32 IndexT;
   uptr pos;
   IndexT cache[kSize];
-  template<typename T, uptr kL1Size, uptr kL2Size> friend class DenseSlabAlloc;
+  template <typename, uptr, uptr, u64>
+  friend class DenseSlabAlloc;
 };
 
-template<typename T, uptr kL1Size, uptr kL2Size>
+template <typename T, uptr kL1Size, uptr kL2Size, u64 kReserved = 0>
 class DenseSlabAlloc {
  public:
   typedef DenseSlabAllocCache Cache;
   typedef typename Cache::IndexT IndexT;
 
-  explicit DenseSlabAlloc(const char *name) {
-    // Check that kL1Size and kL2Size are sane.
-    CHECK_EQ(kL1Size & (kL1Size - 1), 0);
-    CHECK_EQ(kL2Size & (kL2Size - 1), 0);
-    CHECK_GE(1ull << (sizeof(IndexT) * 8), kL1Size * kL2Size);
-    // Check that it makes sense to use the dense alloc.
-    CHECK_GE(sizeof(T), sizeof(IndexT));
-    internal_memset(map_, 0, sizeof(map_));
+  static_assert((kL1Size & (kL1Size - 1)) == 0,
+                "kL1Size must be a power-of-two");
+  static_assert((kL2Size & (kL2Size - 1)) == 0,
+                "kL2Size must be a power-of-two");
+  static_assert((kL1Size * kL2Size) <= (1ull << (sizeof(IndexT) * 8)),
+                "kL1Size/kL2Size are too large");
+  static_assert(((kL1Size * kL2Size - 1) & kReserved) == 0,
+                "reserved bits don't fit");
+  static_assert(sizeof(T) > sizeof(IndexT),
+                "it doesn't make sense to use dense alloc");
+
+  explicit DenseSlabAlloc(LinkerInitialized, const char *name) {
     freelist_ = 0;
     fillpos_ = 0;
     name_ = name;
   }
 
+  explicit DenseSlabAlloc(const char *name)
+      : DenseSlabAlloc(LINKER_INITIALIZED, name) {
+    // It can be very large.
+    // Don't page it in for linker initialized objects.
+    internal_memset(map_, 0, sizeof(map_));
+  }
+
   ~DenseSlabAlloc() {
     for (uptr i = 0; i < kL1Size; i++) {
       if (map_[i] != 0)
diff --git a/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp b/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp
--- a/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_rtl.cpp
@@ -114,17 +114,17 @@
 #endif
 
 Context::Context()
-  : initialized()
-  , report_mtx(MutexTypeReport, StatMtxReport)
-  , nreported()
-  , nmissed_expected()
-  , thread_registry(new(thread_registry_placeholder) ThreadRegistry(
-      CreateThreadContext, kMaxTid, kThreadQuarantineSize, kMaxTidReuse))
-  , racy_mtx(MutexTypeRacy, StatMtxRacy)
-  , racy_stacks()
-  , racy_addresses()
-  , fired_suppressions_mtx(MutexTypeFired, StatMtxFired)
-  , clock_alloc("clock allocator") {
+    : initialized(),
+      report_mtx(MutexTypeReport, StatMtxReport),
+      nreported(),
+      nmissed_expected(),
+      thread_registry(new (thread_registry_placeholder) ThreadRegistry(
+          CreateThreadContext, kMaxTid, kThreadQuarantineSize, kMaxTidReuse)),
+      racy_mtx(MutexTypeRacy, StatMtxRacy),
+      racy_stacks(),
+      racy_addresses(),
+      fired_suppressions_mtx(MutexTypeFired, StatMtxFired),
+      clock_alloc(LINKER_INITIALIZED, "clock allocator") {
   fired_suppressions.reserve(8);
 }
 
diff --git a/compiler-rt/lib/tsan/rtl/tsan_sync.h b/compiler-rt/lib/tsan/rtl/tsan_sync.h
--- a/compiler-rt/lib/tsan/rtl/tsan_sync.h
+++ b/compiler-rt/lib/tsan/rtl/tsan_sync.h
@@ -130,8 +130,8 @@
   static const u32 kFlagMask  = 3u << 30;
   static const u32 kFlagBlock = 1u << 30;
   static const u32 kFlagSync  = 2u << 30;
-  typedef DenseSlabAlloc<MBlock, 1<<16, 1<<12> BlockAlloc;
-  typedef DenseSlabAlloc<SyncVar, 1<<16, 1<<10> SyncAlloc;
+  typedef DenseSlabAlloc<MBlock, 1 << 18, 1 << 12, kFlagMask> BlockAlloc;
+  typedef DenseSlabAlloc<SyncVar, 1 << 20, 1 << 10, kFlagMask> SyncAlloc;
   BlockAlloc block_alloc_;
   SyncAlloc sync_alloc_;
   atomic_uint64_t uid_gen_;
diff --git a/compiler-rt/lib/tsan/rtl/tsan_sync.cpp b/compiler-rt/lib/tsan/rtl/tsan_sync.cpp
--- a/compiler-rt/lib/tsan/rtl/tsan_sync.cpp
+++ b/compiler-rt/lib/tsan/rtl/tsan_sync.cpp
@@ -53,8 +53,8 @@
 }
 
 MetaMap::MetaMap()
-    : block_alloc_("heap block allocator")
-    , sync_alloc_("sync allocator") {
+    : block_alloc_(LINKER_INITIALIZED, "heap block allocator"),
+      sync_alloc_(LINKER_INITIALIZED, "sync allocator") {
   atomic_store(&uid_gen_, 0, memory_order_relaxed);
 }
 
diff --git a/compiler-rt/lib/tsan/tests/unit/CMakeLists.txt b/compiler-rt/lib/tsan/tests/unit/CMakeLists.txt
--- a/compiler-rt/lib/tsan/tests/unit/CMakeLists.txt
+++ b/compiler-rt/lib/tsan/tests/unit/CMakeLists.txt
@@ -1,5 +1,6 @@
 set(TSAN_UNIT_TEST_SOURCES
   tsan_clock_test.cpp
+  tsan_dense_alloc_test.cpp
   tsan_flags_test.cpp
   tsan_mman_test.cpp
   tsan_mutex_test.cpp
diff --git a/compiler-rt/lib/tsan/tests/unit/tsan_dense_alloc_test.cpp b/compiler-rt/lib/tsan/tests/unit/tsan_dense_alloc_test.cpp
--- a/compiler-rt/lib/tsan/tests/unit/tsan_dense_alloc_test.cpp
+++ b/compiler-rt/lib/tsan/tests/unit/tsan_dense_alloc_test.cpp
@@ -26,7 +26,7 @@
   typedef Alloc::IndexT IndexT;
   const int N = 1000;
 
-  Alloc alloc;
+  Alloc alloc("test");
   Cache cache;
   alloc.InitCache(&cache);