diff --git a/tests/test-remotefilelog-datapack.py b/tests/test-remotefilelog-datapack.py
--- a/tests/test-remotefilelog-datapack.py
+++ b/tests/test-remotefilelog-datapack.py
@@ -4,7 +4,6 @@
 import hashlib
 import os
 import random
-import resource
 import shutil
 import stat
 import struct
@@ -39,6 +38,7 @@
 class datapacktestsbase(object):
     def __init__(self, datapackreader, paramsavailable):
         self.datapackreader = datapackreader
+        self.iscdatapack = not paramsavailable
         self.paramsavailable = paramsavailable
 
     def setUp(self):
@@ -276,6 +276,12 @@
     def testPacksCache(self):
         """Test that we remember the most recent packs while fetching the delta
         chain."""
+        # This test will require many file descriptors. Python's mmap objects
+        # will keep an internal fd to support mmap.resize, which could exhaust
+        # the fd limit. Therefore we only run the test with the native code
+        # path, which does not keep fd open for mmaps.
+        if not self.iscdatapack:
+            raise unittest.SkipTest('ignored for Python code path')
 
         packdir = self.makeTempDir()
         deltachains = []
@@ -300,29 +306,20 @@
             self.createPack(chain, packdir)
             deltachains.append(chain)
 
-        try:
-            store = datapackstore(mercurial.ui.ui(), packdir)
+        store = datapackstore(mercurial.ui.ui(), packdir, self.iscdatapack)
 
-            random.shuffle(deltachains)
-            for randomchain in deltachains:
-                revision = random.choice(randomchain)
-                chain = store.getdeltachain(revision[0], revision[1])
+        random.shuffle(deltachains)
+        for randomchain in deltachains:
+            revision = random.choice(randomchain)
+            chain = store.getdeltachain(revision[0], revision[1])
 
-                mostrecentpack = next(iter(store.packs), None)
-                self.assertEquals(
-                    mostrecentpack.getdeltachain(revision[0], revision[1]),
-                    chain
-                )
+            mostrecentpack = next(iter(store.packs), None)
+            self.assertEquals(
+                mostrecentpack.getdeltachain(revision[0], revision[1]),
+                chain
+            )
 
-                self.assertEquals(randomchain.index(revision) + 1, len(chain))
-        except Exception as ex:
-            print('Exception: %r' % ex)
-            # Print out RLIMIT_NOFILE
-            print('RLIMIT_NOFILE: %r'
-                  % (resource.getrlimit(resource.RLIMIT_NOFILE),))
-            # Print debug information about what files are opened by the
-            # current process.
-            os.system('lsof -p %s' % os.getpid())
+            self.assertEquals(randomchain.index(revision) + 1, len(chain))
 
     # perf test off by default since it's slow
     def _testIndexPerf(self):