diff --git a/remotefilelog/fileserverclient.py b/remotefilelog/fileserverclient.py
--- a/remotefilelog/fileserverclient.py
+++ b/remotefilelog/fileserverclient.py
@@ -9,6 +9,7 @@
 
 import hashlib, os, time, io, struct
 import itertools
+import subprocess
 
 from mercurial.i18n import _
 from mercurial.node import hex, bin, nullid
@@ -117,16 +118,56 @@
     gets and sets by communicating with an external process that has the
     cache-specific implementation.
     """
-    def __init__(self):
+    def __init__(self, repo):
+        self.repo = repo
         self.pipeo = self.pipei = self.pipee = None
         self.subprocess = None
         self.connected = False
+        # default Linux pipe buffer size for kernels >=2.6.11
+        self.pipei_bufsize = 65536 if os.name != 'nt' else 4096
+
+    def _defaultconnect(self, cachecommand):
+        self.pipei, self.pipeo, self.pipee, self.subprocess = \
+            util.popen4(cachecommand)
+
+    def _windowsconnect(self, cachecommand):
+        import msvcrt
+        from _subprocess import CreatePipe
+        # By default, Windows has a pipe buffer size of 4K. This is the
+        # reason why we saw deadlocks in _getfiles on Windows but not on POSIX
+        # To circumvent this, we ask the system to create a pipe with
+        # a large enough buffer.
+        # Unfortunately, we can't do it cleanly with subprocess.Popen API:
+        # it's bufsize argument is related to the in-process (setvbuf) buffer,
+        # not the OS pipe buffer itself.
+        # This method converts between three types of file specifiers:
+        # - native Windows HANDLEs, returned by CreatePipe
+        # - C Runtime file descriptors, obtained by open_osfhandle
+        # - Python file-like objects, obtained by os.fdopen
+        handles = CreatePipe(None, self.pipei_bufsize)
+        # subprocess.py cannot take real HANDLEs, needs fds
+        rfd, wfd = [msvcrt.open_osfhandle(h, 0) for h in handles]
+        self.subprocess = subprocess.Popen(cachecommand, newlines=False,
+                                           close_fds=False, env=None,
+                                           stdin=rfd,  # manual pipe
+                                           stdout=subprocess.PIPE,
+                                           stderr=subprocess.PIPE)
+        self.pipeo = self.subprocess.stdout
+        self.pipee = self.subprocess.stderr
+        # turn file descriptor into a file-like object
+        # bufsize=-1 means "use default C Runtime buffer for an open fd"
+        self.pipei = os.fdopen(wfd, 'wb', bufsize=-1)
 
     def connect(self, cachecommand):
         if self.pipeo:
             raise error.Abort(_("cache connection already open"))
-        self.pipei, self.pipeo, self.pipee, self.subprocess = \
-            util.popen4(cachecommand)
+        custompipei = self.repo.ui.configbool('remotefilelog',
+                                              'windows.custompipei', True)
+        if os.name == 'nt' and custompipei:
+            # to ensure we have pipe buffer of the same size as on Linux
+            self._windowsconnect(cachecommand)
+        else:
+            self._defaultconnect(cachecommand)
         self.connected = True
 
     def close(self):
@@ -266,7 +307,7 @@
 
         self.debugoutput = ui.configbool("remotefilelog", "debug")
 
-        self.remotecache = cacheconnection()
+        self.remotecache = cacheconnection(repo)
         self.connpool = connectionpool.connectionpool(repo)
 
     def setstore(self, datastore, historystore, writedata, writehistory):
diff --git a/tests/test-check-config-hg.t b/tests/test-check-config-hg.t
--- a/tests/test-check-config-hg.t
+++ b/tests/test-check-config-hg.t
@@ -70,6 +70,7 @@
   undocumented: remotefilelog.shallowtrees (bool)
   undocumented: remotefilelog.validatecache (str) ['on']
   undocumented: remotefilelog.validatecachelog (str)
+  undocumented: remotefilelog.windows.custompipei (bool) [True]
   undocumented: simplecache.cachedir (str)
   undocumented: simplecache.caches (list) [['local']]
   undocumented: simplecache.evictionpercent (int) [50]