Add support for using multiple connections

The -o max_conns=N option causes multiple SSH processes and response processing threads to
be created. This means that e.g. reading a large file no longer blocks all access to the
filesystem.

The connection is chosen by checking the per-connection statistics:

  1. Choose connection with least outstanding requests; if it's a tie,
  2. choose connection with least directory handles; if it's a tie,
  3. choose connection with least file handles; if it's a tie,
  4. choose connection which has already been established.

The implementation assumes that the max_conns values will be small; it
uses linear search.

Example benchmark:

With single connection:

$ sshfs -o max_conns=1,workaround=nobuflimit ebox: mnt
$ cat mnt/tmp/bigfile > /dev/null &
$ time find mnt > /dev/null

real	1m50.432s
user	0m0.133s
sys	0m0.467s

With multiple connections:

$ ~/in-progress/sshfs/build/sshfs -o max_conns=5,workaround=nobuflimit ebox: mnt
$ cat mnt/tmp/bigfile > /dev/null &
$ time find mnt > /dev/null

real	1m15.338s
user	0m0.142s
sys	0m0.491s

This feature was implemented to large extend by Timo Savola <timo.savola@iki.fi>. Thanks
to CEA.fr for sponsoring the remaining work to complete this feature and integrate it into
SSHFS!

1 files changed, 5 insertions, 1 deletions

diff --git a/test/test_sshfs.py b/test/test_sshfs.py
index 995ff00..d873a63 100755
--- a/test/test_sshfs.py
+++ b/test/test_sshfs.py
@@ -33,7 +33,8 @@ def name_generator(__ctr=[0]):
 @pytest.mark.parametrize("debug", (False, True))
 @pytest.mark.parametrize("cache_timeout", (0,1))
 @pytest.mark.parametrize("sync_rd", (True, False))
-def test_sshfs(tmpdir, debug, cache_timeout, sync_rd, capfd):
+@pytest.mark.parametrize("multiconn", (True,False))
+def test_sshfs(tmpdir, debug, cache_timeout, sync_rd, multiconn, capfd):
     
     # Avoid false positives from debug messages
     #if debug:
@@ -77,6 +78,9 @@ def test_sshfs(tmpdir, debug, cache_timeout, sync_rd, capfd):
     cmdline += [ '-o', 'entry_timeout=0',
                  '-o', 'attr_timeout=0' ]
 
+    if multiconn:
+        cmdline += [ '-o', 'max_conns=3',
+                     '-o', 'workaround=nobuflimit' ]
     
     new_env = dict(os.environ) # copy, don't modify