Initial attempt to fix resource usage

Reference counting is now done manually, but it seems that things can
still go wrong at least during testing

doc/source/changes.rst

@@ -2,6 +2,12 @@
 Changelog
 #########
 
+**********
+v0.8.6
+**********
+- Fixed issue with resources never being freed as mmaps were never closed.
+- Client counting is now done manually, instead of relying on pyton's reference count
+
 **********
 v0.8.5
 **********

smmap/mman.py

@@ -8,7 +8,6 @@
     buffer,
 )
 
-from weakref import ref
 import sys
 from functools import reduce
 
@@ -55,8 +54,7 @@ def _destroy(self):
             # Actual client count, which doesn't include the reference kept by the manager, nor ours
             # as we are about to be deleted
             try:
-                num_clients = self._rlist.client_count() - 2
-                if num_clients == 0 and len(self._rlist) == 0:
+                if len(self._rlist) == 0:
                     # Free all resources associated with the mapped file
                     self._manager._fdict.pop(self._rlist.path_or_fd())
                 # END remove regions list from manager
@@ -78,7 +76,7 @@ def _copy_from(self, rhs):
         self._size = rhs._size
 
         if self._region is not None:
-            self._region.increment_usage_count()
+            self._region.increment_client_count()
         # END handle regions
 
     def __copy__(self):
@@ -126,20 +124,22 @@ def use_region(self, offset=0, size=0, flags=0):
 
         if need_region:
             self._region = man._obtain_region(self._rlist, offset, size, flags, False)
+            self._region.increment_client_count()
         # END need region handling
 
-        self._region.increment_usage_count()
         self._ofs = offset - self._region._b
         self._size = min(size, self._region.ofs_end() - offset)
 
         return self
 
     def unuse_region(self):
-        """Unuse the ucrrent region. Does nothing if we have no current region
+        """Unuse the current region. Does nothing if we have no current region
 
         **Note:** the cursor unuses the region automatically upon destruction. It is recommended
         to un-use the region once you are done reading from it in persistent cursors as it
         helps to free up resource more quickly"""
+        if self._region is not None:
+            self._region.increment_client_count(-1)
         self._region = None
         # note: should reset ofs and size, but we spare that for performance. Its not
         # allowed to query information if we are not valid !
@@ -184,12 +184,10 @@ def size(self):
         """:return: amount of bytes we point to"""
         return self._size
 
-    def region_ref(self):
-        """:return: weak ref to our mapped region.
+    def region(self):
+        """:return: our mapped region, or None if nothing is mapped yet
         :raise AssertionError: if we have no current region. This is only useful for debugging"""
-        if self._region is None:
-            raise AssertionError("region not set")
-        return ref(self._region)
+        return self._region
 
     def includes_ofs(self, ofs):
         """:return: True if the given absolute offset is contained in the cursors
@@ -311,8 +309,8 @@ def _collect_lru_region(self, size):
             lru_list = None
             for regions in self._fdict.values():
                 for region in regions:
-                    # check client count - consider that we keep one reference ourselves !
-                    if (region.client_count() - 2 == 0 and
+                    # check client count - if it's 1, it's just us
+                    if (region.client_count() == 1 and
                             (lru_region is None or region._uc < lru_region._uc)):
                         lru_region = region
                         lru_list = regions
@@ -326,6 +324,7 @@ def _collect_lru_region(self, size):
 
             num_found += 1
             del(lru_list[lru_list.index(lru_region)])
+            lru_region.increment_client_count(-1)
             self._memory_size -= lru_region.size()
             self._handle_count -= 1
         # END while there is more memory to free
@@ -449,7 +448,7 @@ def force_map_handle_removal_win(self, base_path):
         for path, rlist in self._fdict.items():
             if path.startswith(base_path):
                 for region in rlist:
-                    region._mf.close()
+                    region.release()
                     num_closed += 1
             # END path matches
         # END for each path

smmap/test/test_mman.py

@@ -119,29 +119,29 @@ def test_memman_operation(self):
                 # window size is 0 for static managers, hence size will be 0. We take that into consideration
                 size = man.window_size() // 2
                 assert c.use_region(base_offset, size).is_valid()
-                rr = c.region_ref()
-                assert rr().client_count() == 2  # the manager and the cursor and us
+                rr = c.region()
+                assert rr.client_count() == 2  # the manager and the cursor and us
 
                 assert man.num_open_files() == 1
                 assert man.num_file_handles() == 1
-                assert man.mapped_memory_size() == rr().size()
+                assert man.mapped_memory_size() == rr.size()
 
                 # assert c.size() == size        # the cursor may overallocate in its static version
                 assert c.ofs_begin() == base_offset
-                assert rr().ofs_begin() == 0        # it was aligned and expanded
+                assert rr.ofs_begin() == 0        # it was aligned and expanded
                 if man.window_size():
                     # but isn't larger than the max window (aligned)
-                    assert rr().size() == align_to_mmap(man.window_size(), True)
+                    assert rr.size() == align_to_mmap(man.window_size(), True)
                 else:
-                    assert rr().size() == fc.size
+                    assert rr.size() == fc.size
                 # END ignore static managers which dont use windows and are aligned to file boundaries
 
                 assert c.buffer()[:] == data[base_offset:base_offset + (size or c.size())]
 
                 # obtain second window, which spans the first part of the file - it is a still the same window
                 nsize = (size or fc.size) - 10
                 assert c.use_region(0, nsize).is_valid()
-                assert c.region_ref()() == rr()
+                assert c.region() == rr
                 assert man.num_file_handles() == 1
                 assert c.size() == nsize
                 assert c.ofs_begin() == 0
@@ -154,15 +154,15 @@ def test_memman_operation(self):
                 if man.window_size():
                     assert man.num_file_handles() == 2
                     assert c.size() < size
-                    assert c.region_ref()() is not rr()  # old region is still available, but has not curser ref anymore
-                    assert rr().client_count() == 1  # only held by manager
+                    assert c.region() is not rr  # old region is still available, but has not curser ref anymore
+                    assert rr.client_count() == 1  # only held by manager
                 else:
                     assert c.size() < fc.size
                 # END ignore static managers which only have one handle per file
-                rr = c.region_ref()
-                assert rr().client_count() == 2  # manager + cursor
-                assert rr().ofs_begin() < c.ofs_begin()  # it should have extended itself to the left
-                assert rr().ofs_end() <= fc.size  # it cannot be larger than the file
+                rr = c.region()
+                assert rr.client_count() == 2  # manager + cursor
+                assert rr.ofs_begin() < c.ofs_begin()  # it should have extended itself to the left
+                assert rr.ofs_end() <= fc.size  # it cannot be larger than the file
                 assert c.buffer()[:] == data[base_offset:base_offset + (size or c.size())]
 
                 # unising a region makes the cursor invalid

smmap/test/test_util.py

@@ -88,12 +88,7 @@ def test_region(self):
         # auto-refcount
         assert rfull.client_count() == 1
         rfull2 = rfull
-        assert rfull.client_count() == 2
-
-        # usage
-        assert rfull.usage_count() == 0
-        rfull.increment_usage_count()
-        assert rfull.usage_count() == 1
+        assert rfull.client_count() == 1, "no auto-counting"
 
         # window constructor
         w = MapWindow.from_region(rfull)
@@ -106,8 +101,6 @@ def test_region_list(self):
         for item in (fc.path, fd):
             ml = MapRegionList(item)
 
-            assert ml.client_count() == 1
-
             assert len(ml) == 0
             assert ml.path_or_fd() == item
             assert ml.file_size() == fc.size

smmap/util.py

@@ -177,6 +177,8 @@ def __init__(self, path_or_fd, ofs, size, flags=0):
                 os.close(fd)
             # END only close it if we opened it
         # END close file handle
+        # We assume the first one to use us keeps us around
+        self.increment_client_count()
 
     def _read_into_memory(self, fd, offset, size):
         """:return: string data as read from the given file descriptor, offset and size """
@@ -222,17 +224,25 @@ def includes_ofs(self, ofs):
 
     def client_count(self):
         """:return: number of clients currently using this region"""
-        from sys import getrefcount
-        # -1: self on stack, -1 self in this method, -1 self in getrefcount
-        return getrefcount(self) - 3
-
-    def usage_count(self):
-        """:return: amount of usages so far"""
         return self._uc
 
-    def increment_usage_count(self):
-        """Adjust the usage count by the given positive or negative offset"""
-        self._uc += 1
+    def increment_client_count(self, ofs = 1):
+        """Adjust the usage count by the given positive or negative offset.
+        If usage count equals 0, we will auto-release our resources
+        :return: True if we released resources, False otherwise. In the latter case, we can still be used"""
+        self._uc += ofs
+        assert self._uc > -1, "Increments must match decrements, usage counter negative: %i" % self._uc
+
+        if self.client_count() == 0:
+            self.release()
+            return True
+        else:
+            return False
+        # end handle release
+
+    def release(self):
+        """Release all resources this instance might hold. Must only be called if there usage_count() is zero"""
+        self._mf.close()
 
     # re-define all methods which need offset adjustments in compatibility mode
     if _need_compat_layer:
@@ -268,11 +278,6 @@ def __init__(self, path_or_fd):
         self._path_or_fd = path_or_fd
         self._file_size = None
 
-    def client_count(self):
-        """:return: amount of clients which hold a reference to this instance"""
-        from sys import getrefcount
-        return getrefcount(self) - 3
-
     def path_or_fd(self):
         """:return: path or file descriptor we are attached to"""
         return self._path_or_fd