diff --git a/python/ray/internal/internal_api.py b/python/ray/internal/internal_api.py
index de5e89c75..43af66aba 100644
--- a/python/ray/internal/internal_api.py
+++ b/python/ray/internal/internal_api.py
@@ -112,6 +112,10 @@ def store_stats_summary(reply):
             round(
                 100 * reply.store_stats.object_store_bytes_used /
                 reply.store_stats.object_store_bytes_avail, 2)))
+    if reply.store_stats.object_store_bytes_fallback > 0:
+        store_summary += ("Plasma filesystem mmap usage: {} MiB\n".format(
+            int(reply.store_stats.object_store_bytes_fallback /
+                (1024 * 1024))))
     if reply.store_stats.spill_time_total_s > 0:
         store_summary += (
             "Spilled {} MiB, {} objects, avg write throughput {} MiB/s\n".
diff --git a/python/ray/tests/test_plasma_unlimited.py b/python/ray/tests/test_plasma_unlimited.py
index 4a719cc90..2b8500168 100644
--- a/python/ray/tests/test_plasma_unlimited.py
+++ b/python/ray/tests/test_plasma_unlimited.py
@@ -17,7 +17,7 @@ def _init_ray():
         _system_config={"plasma_unlimited": 1})
 
 
-def _check_spilled_mb(address, spilled=None, restored=None):
+def _check_spilled_mb(address, spilled=None, restored=None, fallback=None):
     def ok():
         s = memory_summary(address=address["redis_address"], stats_only=True)
         print(s)
@@ -33,6 +33,13 @@ def _check_spilled_mb(address, spilled=None, restored=None):
         else:
             if "Spilled" in s:
                 return False
+        if fallback:
+            if "Plasma filesystem mmap usage: {} MiB".format(
+                    fallback) not in s:
+                return False
+        else:
+            if "Plasma filesystem mmap usage:" in s:
+                return False
         return True
 
     wait_for_condition(ok, timeout=3, retry_interval_ms=1000)
@@ -50,7 +57,7 @@ def test_fallback_when_spilling_impossible_on_put():
         x2p = ray.get(x2)
         del x1p
         del x2p
-        _check_spilled_mb(address, spilled=None)
+        _check_spilled_mb(address, spilled=None, fallback=400)
     finally:
         ray.shutdown()
 
@@ -82,7 +89,7 @@ def test_fallback_when_spilling_impossible_on_get():
         _check_spilled_mb(address, spilled=800, restored=400)
         # x2 will be restored, triggering a fallback allocation.
         x2p = ray.get(x2)
-        _check_spilled_mb(address, spilled=800, restored=800)
+        _check_spilled_mb(address, spilled=800, restored=800, fallback=400)
         del x1p
         del x2p
     finally:
@@ -130,7 +137,7 @@ def test_task_unlimited():
 
         # round 1
         ray.get(consume.remote(refs))
-        _check_spilled_mb(address, spilled=500, restored=400)
+        _check_spilled_mb(address, spilled=500, restored=400, fallback=400)
 
         del x2p
         del sentinel
@@ -158,7 +165,7 @@ def test_task_unlimited_multiget_args():
             return os.getpid()
 
         ray.get([consume.remote(refs) for _ in range(1000)])
-        _check_spilled_mb(address, spilled=2000, restored=2000)
+        _check_spilled_mb(address, spilled=2000, restored=2000, fallback=2000)
         del x2p
     finally:
         ray.shutdown()
diff --git a/src/ray/object_manager/object_manager.cc b/src/ray/object_manager/object_manager.cc
index 17c8d2b2d..3013df04f 100644
--- a/src/ray/object_manager/object_manager.cc
+++ b/src/ray/object_manager/object_manager.cc
@@ -901,6 +901,7 @@ std::string ObjectManager::DebugString() const {
 void ObjectManager::RecordMetrics() const {
   stats::ObjectStoreAvailableMemory().Record(config_.object_store_memory - used_memory_);
   stats::ObjectStoreUsedMemory().Record(used_memory_);
+  stats::ObjectStoreFallbackMemory().Record(plasma::PlasmaAllocator::FallbackAllocated());
   stats::ObjectStoreLocalObjects().Record(local_objects_.size());
   stats::ObjectManagerPullRequests().Record(pull_manager_->NumActiveRequests());
 }
@@ -908,6 +909,7 @@ void ObjectManager::RecordMetrics() const {
 void ObjectManager::FillObjectStoreStats(rpc::GetNodeStatsReply *reply) const {
   auto stats = reply->mutable_store_stats();
   stats->set_object_store_bytes_used(used_memory_);
+  stats->set_object_store_bytes_fallback(plasma::PlasmaAllocator::FallbackAllocated());
   stats->set_object_store_bytes_avail(config_.object_store_memory);
   stats->set_num_local_objects(local_objects_.size());
   stats->set_consumed_bytes(plasma::plasma_store_runner->GetConsumedBytes());
diff --git a/src/ray/object_manager/plasma/dlmalloc.cc b/src/ray/object_manager/plasma/dlmalloc.cc
index 87fbcd5a4..e800c5f61 100644
--- a/src/ray/object_manager/plasma/dlmalloc.cc
+++ b/src/ray/object_manager/plasma/dlmalloc.cc
@@ -73,6 +73,11 @@ constexpr int GRANULARITY_MULTIPLIER = 2;
 // Combined with MAP_POPULATE, this can guarantee we never run into SIGBUS errors.
 static bool allocated_once = false;
 
+// Populated on the first allocation so we can track which allocations fall within
+// the initial region vs outside.
+static char *initial_region_ptr = nullptr;
+static size_t initial_region_size = 0;
+
 static void *pointer_advance(void *p, ptrdiff_t n) { return (unsigned char *)p + n; }
 
 static void *pointer_retreat(void *p, ptrdiff_t n) { return (unsigned char *)p - n; }
@@ -141,8 +146,12 @@ void create_and_mmap_buffer(int64_t size, void **pointer, int *fd) {
       RAY_LOG(ERROR)
           << "  (this probably means you have to increase /proc/sys/vm/nr_hugepages)";
     }
+  } else if (!allocated_once) {
+    initial_region_ptr = static_cast<char *>(*pointer);
+    initial_region_size = size;
   }
 }
+
 #endif
 
 void *fake_mmap(size_t size) {
@@ -211,6 +220,14 @@ int fake_munmap(void *addr, int64_t size) {
 
 void SetMallocGranularity(int value) { change_mparam(M_GRANULARITY, value); }
 
+// Returns whether the given pointer is outside the initially allocated region.
+bool IsOutsideInitialAllocation(void *p) {
+  if (initial_region_ptr == nullptr) {
+    return false;
+  }
+  return (p < initial_region_ptr) || (p >= (initial_region_ptr + initial_region_size));
+}
+
 const PlasmaStoreInfo *plasma_config;
 
 }  // namespace plasma
diff --git a/src/ray/object_manager/plasma/plasma_allocator.cc b/src/ray/object_manager/plasma/plasma_allocator.cc
index 6e5c373b0..1fe5bbeea 100644
--- a/src/ray/object_manager/plasma/plasma_allocator.cc
+++ b/src/ray/object_manager/plasma/plasma_allocator.cc
@@ -23,6 +23,8 @@
 
 namespace plasma {
 
+bool IsOutsideInitialAllocation(void *ptr);
+
 extern "C" {
 void *dlmemalign(size_t alignment, size_t bytes);
 void dlfree(void *mem);
@@ -35,6 +37,7 @@ const int M_MMAP_THRESHOLD = -3;
 
 int64_t PlasmaAllocator::footprint_limit_ = 0;
 int64_t PlasmaAllocator::allocated_ = 0;
+int64_t PlasmaAllocator::fallback_allocated_ = 0;
 
 void *PlasmaAllocator::Memalign(size_t alignment, size_t bytes) {
   if (!RayConfig::instance().plasma_unlimited()) {
@@ -54,7 +57,6 @@ void *PlasmaAllocator::Memalign(size_t alignment, size_t bytes) {
   return mem;
 }
 
-// TODO(ekl) we should track these allocations separately from the overall footprint.
 void *PlasmaAllocator::DiskMemalignUnlimited(size_t alignment, size_t bytes) {
   // Forces allocation as a separate file.
   RAY_CHECK(dlmallopt(M_MMAP_THRESHOLD, 0));
@@ -64,13 +66,18 @@ void *PlasmaAllocator::DiskMemalignUnlimited(size_t alignment, size_t bytes) {
   if (!mem) {
     return nullptr;
   }
+  RAY_CHECK(IsOutsideInitialAllocation(mem));
   allocated_ += bytes;
+  fallback_allocated_ += bytes;
   return mem;
 }
 
 void PlasmaAllocator::Free(void *mem, size_t bytes) {
   dlfree(mem);
   allocated_ -= bytes;
+  if (RayConfig::instance().plasma_unlimited() && IsOutsideInitialAllocation(mem)) {
+    fallback_allocated_ -= bytes;
+  }
 }
 
 void PlasmaAllocator::SetFootprintLimit(size_t bytes) {
@@ -81,4 +88,6 @@ int64_t PlasmaAllocator::GetFootprintLimit() { return footprint_limit_; }
 
 int64_t PlasmaAllocator::Allocated() { return allocated_; }
 
+int64_t PlasmaAllocator::FallbackAllocated() { return fallback_allocated_; }
+
 }  // namespace plasma
diff --git a/src/ray/object_manager/plasma/plasma_allocator.h b/src/ray/object_manager/plasma/plasma_allocator.h
index eb589814c..fb5adebec 100644
--- a/src/ray/object_manager/plasma/plasma_allocator.h
+++ b/src/ray/object_manager/plasma/plasma_allocator.h
@@ -58,8 +58,13 @@ class PlasmaAllocator {
   /// \return Number of bytes allocated by Plasma so far.
   static int64_t Allocated();
 
+  /// Get the number of bytes fallback allocated by Plasma so far.
+  /// \return Number of bytes fallback allocated by Plasma so far.
+  static int64_t FallbackAllocated();
+
  private:
   static int64_t allocated_;
+  static int64_t fallback_allocated_;
   static int64_t footprint_limit_;
 };
 
diff --git a/src/ray/protobuf/node_manager.proto b/src/ray/protobuf/node_manager.proto
index 87fb09a83..f9d95c5de 100644
--- a/src/ray/protobuf/node_manager.proto
+++ b/src/ray/protobuf/node_manager.proto
@@ -137,10 +137,12 @@ message ObjectStoreStats {
   int64 object_store_bytes_used = 7;
   // The max capacity of the object store.
   int64 object_store_bytes_avail = 8;
+  // The number of bytes allocated from the filesystem (fallback allocs).
+  int64 object_store_bytes_fallback = 9;
   // The number of local objects total.
-  int64 num_local_objects = 9;
+  int64 num_local_objects = 10;
   // The number of plasma object bytes that are consumed by core workers.
-  int64 consumed_bytes = 10;
+  int64 consumed_bytes = 11;
 }
 
 message GetNodeStatsReply {
diff --git a/src/ray/raylet/node_manager.cc b/src/ray/raylet/node_manager.cc
index 11c2cb9f0..e503c6cf6 100644
--- a/src/ray/raylet/node_manager.cc
+++ b/src/ray/raylet/node_manager.cc
@@ -2208,6 +2208,9 @@ rpc::ObjectStoreStats AccumulateStoreStats(
                                             cur_store.object_store_bytes_used());
     store_stats.set_object_store_bytes_avail(store_stats.object_store_bytes_avail() +
                                              cur_store.object_store_bytes_avail());
+    store_stats.set_object_store_bytes_fallback(
+        store_stats.object_store_bytes_fallback() +
+        cur_store.object_store_bytes_fallback());
     store_stats.set_num_local_objects(store_stats.num_local_objects() +
                                       cur_store.num_local_objects());
     store_stats.set_consumed_bytes(store_stats.consumed_bytes() +
diff --git a/src/ray/stats/metric_defs.h b/src/ray/stats/metric_defs.h
index 7b968cbc4..28904bf88 100644
--- a/src/ray/stats/metric_defs.h
+++ b/src/ray/stats/metric_defs.h
@@ -59,6 +59,10 @@ static Gauge ObjectStoreUsedMemory(
     "object_store_used_memory",
     "Amount of memory currently occupied in the object store.", "bytes");
 
+static Gauge ObjectStoreFallbackMemory(
+    "object_store_fallback_memory",
+    "Amount of memory in fallback allocations in the filesystem.", "bytes");
+
 static Gauge ObjectStoreLocalObjects("object_store_num_local_objects",
                                      "Number of objects currently in the object store.",
                                      "objects");