.

wcfs/internal/mm.pyx

@@ -40,6 +40,12 @@ cpdef enum:
     MADV_SEQUENTIAL = mman.MADV_SEQUENTIAL
     MADV_WILLNEED   = mman.MADV_WILLNEED
     MADV_DONTNEED   = mman.MADV_DONTNEED
+    MADV_FREE       = mman.MADV_FREE
+    MADV_REMOVE     = mman.MADV_REMOVE
+
+    MS_ASYNC        = mman.MS_ASYNC
+    MS_SYNC         = mman.MS_SYNC
+    MS_INVALIDATE   = mman.MS_INVALIDATE
 
 # incore returns bytearray vector indicating whether page of mem is in core or not.
 #
@@ -78,7 +84,7 @@ def lock(const unsigned char[::1] mem not None, int flags):
     if err:
         PyErr_SetFromErrno(OSError)
 
-    return  # ok
+    return
 
 
 # unlock unlocks mem pages from being pinned in RAM.
@@ -90,7 +96,7 @@ def unlock(const unsigned char[::1] mem not None):
     if err:
         PyErr_SetFromErrno(OSError)
 
-    return  # ok
+    return
 
 
 from posix.types cimport off_t
@@ -114,7 +120,7 @@ def map_into_ro(unsigned char[::1] mem not None, int fd, off_t offset):
     if addr == mman.MAP_FAILED:
         PyErr_SetFromErrno(OSError)
 
-    return  # ok
+    return
 
 # unmap unmaps memory covered by mem.
 def unmap(const unsigned char[::1] mem not None):
@@ -125,7 +131,7 @@ def unmap(const unsigned char[::1] mem not None):
     if err:
         PyErr_SetFromErrno(OSError)
 
-    return  # ok
+    return
 
 
 # advise advises kernel about use of mem's memory.
@@ -139,4 +145,18 @@ def advise(const unsigned char[::1] mem not None, int advice):
     if err:
         PyErr_SetFromErrno(OSError)
 
-    return  # ok
+    return
+
+
+# sync asks the kernel to synchronize the file with a memory map.
+#
+# see msync(2) for details.
+def sync(const unsigned char[::1] mem not None, int flags):
+    cdef const void *addr = &mem[0]
+    cdef size_t      size = mem.shape[0]
+
+    cdef err = mman.msync(<void *>addr, size, flags)
+    if err:
+        PyErr_SetFromErrno(OSError)
+
+    return

wcfs/internal/wcfs_test.pyx

@@ -26,6 +26,7 @@ from libc.signal cimport SIGBUS
 from libc.stdlib cimport abort
 from libc.string cimport strlen
 from posix.unistd cimport write, sleep
+from posix.types cimport off_t
 
 from cpython.exc cimport PyErr_SetFromErrno
 from cpython.pystate cimport PyGILState_Ensure, PyGILState_Release, PyGILState_STATE
@@ -43,6 +44,18 @@ def read_nogil(const unsigned char[::1] mem not None) -> bytes:
     return bytes(bytearray([b]))
 
 
+cdef extern from "<fcntl.h>" nogil:
+    int posix_fadvise(int fd, off_t offset, off_t len, int advice);
+    enum: POSIX_FADV_DONTNEED
+
+# fadvise_dontneed teels the kernel that file<fd>[offset +len) is not needed.
+#
+# see fadvise(2) for details.
+def fadvise_dontneed(int fd, off_t offset, off_t len):
+    cdef int err = posix_fadvise(fd, offset, len, POSIX_FADV_DONTNEED)
+    if err:
+        PyErr_SetFromErrno(OSError)
+
 # ---- signal handling ----
 # XXX -> golang.signal ?
 

wcfs/wcfs_test.py

@@ -42,7 +42,7 @@ from zodbtools.util import ashex as h, fromhex
 from pytest import raises
 from six import reraise
 from .internal import mm
-from .internal.wcfs_test import read_nogil, install_sigbus_trap
+from .internal.wcfs_test import read_nogil, install_sigbus_trap, fadvise_dontneed
 
 # setup:
 # - create test database, compute zurl and mountpoint for wcfs
@@ -1553,11 +1553,17 @@ def test_wcfs_no_pin_twice():
     assert w.pinned == {2:at1}
 
     # drop file[blk] from cache, access again -> no pin message sent the second time
-    print('\n\n\n\n\nABCDEF\n\n\n')
+    #
+    # ( we need both madvise(DONTNEED) and fadvise(DONTNEED) - given only one of
+    #   those the kernel won't release the page from pagecache; madvise does
+    #   not work without munlock. )
+    mm.unlock(f._blk(2))
     mm.advise(f._blk(2), mm.MADV_DONTNEED)
+    fadvise_dontneed(f.f.fileno(), 2*blksize, 1*blksize)
     f.assertCache([0,0,0])
 
-    # XXX
+    f.assertBlk(2, 'c2', {wl: {}})
+    f.assertCache([0,0,1])
 
 
 # verify watching for 2 files over single watch link.