change compress level to 6 from default 9 to accelerate compress (#593)

Author: taipinghu

dpgen/dispatcher/SSHContext.py

@@ -280,7 +280,7 @@ def _put_files(self,
         os.chdir(self.local_root)
         if os.path.isfile(of) :
             os.remove(of)
-        with tarfile.open(of, "w:gz", dereference = dereference) as tar:
+        with tarfile.open(of, "w:gz", dereference = dereference, compresslevel=6) as tar:
             for ii in files :
                 tar.add(ii)
         os.chdir(cwd)