diff --git a/README.md b/README.md
index c1d9c38e5416221d7ecccf76542cf1cebdce1880..9a15da95faea37ac2efa4e8994c0654105f82a9f 100644
--- a/README.md
+++ b/README.md
@@ -54,7 +54,7 @@ Then copy your resulting wheel and install it via pip on the target system.
 
 ## v0.5.3
 
-* added `disable_mmap` and `enable_mmap` into `VarlenSeries`
+* added `disable_mmap`, `enable_mmap` and `open_chunks_mmap_size` into `VarlenSeries`
 
 ## v0.5.2
 
diff --git a/setup.py b/setup.py
index 6382a8a8863613c4c8c357b68068eacf3b4e6972..1ed60fa7247870da07fbf1427cc64506f297b7b7 100644
--- a/setup.py
+++ b/setup.py
@@ -41,7 +41,7 @@ ext_modules = build([Multibuild('tempsdb', find_pyx('tempsdb'), **ext_kwargs), ]
                      **cythonize_kwargs)
 
 setup(name='tempsdb',
-      version='0.5.3a1',
+      version='0.5.3',
       packages=find_packages(include=['tempsdb', 'tempsdb.*']),
       install_requires=['satella>=2.14.24', 'ujson'],
       ext_modules=ext_modules,
diff --git a/tempsdb/database.pyx b/tempsdb/database.pyx
index 62c340c8fe8de673bf9e4f0fb7c963b2ae1d6ad3..c74171da66f25da501d5707e95a3179620e4c47d 100644
--- a/tempsdb/database.pyx
+++ b/tempsdb/database.pyx
@@ -230,6 +230,8 @@ cdef class Database:
         :return: new variable length series
         :raises AlreadyExists: series with given name already exists
         """
+        from .varlen import create_varlen_series
+
         cdef:
             VarlenSeries series
             str path = os.path.join(self.path, 'varlen', name)
diff --git a/tempsdb/varlen.pxd b/tempsdb/varlen.pxd
index ac2feb9d2ceebb0ee837dd92b9bd0f59ec7fc698..1b125279e8cebb0849c1506fc6bed0d00c5d96a7 100644
--- a/tempsdb/varlen.pxd
+++ b/tempsdb/varlen.pxd
@@ -20,6 +20,7 @@ cdef class VarlenSeries:
 
     cpdef int enable_mmap(self) except -1
     cpdef int disable_mmap(self) except -1
+    cpdef unsigned long open_chunks_mmap_size(self)
     cpdef int mark_synced_up_to(self, unsigned long long timestamp) except -1
     cpdef int close(self, bint force=*) except -1
     cpdef int delete(self) except -1
diff --git a/tempsdb/varlen.pyx b/tempsdb/varlen.pyx
index f381b956e4165dea5f4af7b52bb72207c19e4b27..046fccce5cb8fd677785f659e26766fc585f5c81 100644
--- a/tempsdb/varlen.pyx
+++ b/tempsdb/varlen.pyx
@@ -651,6 +651,17 @@ cdef class VarlenSeries:
         """
         return self.length_profile[-1 if index >= len(self.length_profile) else index]
 
+    cpdef unsigned long open_chunks_mmap_size(self):
+        """
+        :return: total area of memory taken by mmaps, in bytes
+        """
+        cdef:
+            unsigned long long total = 0
+            TimeSeries series
+        for series in self.series:
+            total += series.open_chunks_mmap_size()
+        return total
+
     cpdef int close(self, bint force=False) except -1:
         """
         Close this series.