[mod.os] The High Cost of Opens in the UNIX Environment

carla@cs.duke.edu (Carla Ellis) (04/24/87)

       The High Cost of Opens in the UNIX Environment


                         Rick Floyd
                Computer Science Department
                The University of Rochester
                 Rochester, New York  14627

                   Carla Schlatter Ellis
               Department of Computer Science
                      Duke University
                Durham, North Carolina 27706




                          ABSTRACT


     Hierarchical  name  spaces   modelled   upon   the
     directory  structure  of  the UNIX file system are
     rapidly    becoming    a     defacto     standard.
     Understanding  and improving the behavior of these
     hierarchically structured file systems has,  until
     recently,  been  hampered by a lack of information
     on the ways in which they are used.

          The purpose of this paper is to  examine  the
     overhead of name resolution in accessing files and
     the  potential  effectiveness  of  caching   whole
     directory   nodes   using   information   we  have
     collected on file and directory reference patterns
     in a UNIX environment.

          We prove the  conjecture  that  the  cost  of
     opening  a file is very significant, identify some
     of    the    causes,    and    demonstrate    that
     implementations  using  directory  caching  can be
     highly successful.