Page 53 - slides.dvi
P. 53

⇒
                                                                                          •
                      •
                                                    •
                                                            •
                                                                                                   •
                                                                            –
               a
   Operating
                                                                                                               TLB
                                                            Hit
                                                                                    use
                                                    e.g.
               13%
   Systems
                                             100ns,
                                                                     space
                                                                                          Context
                      Increase
   —
                                                                            Today
                              effective
                                                            ratio
                                     assuming
                                                                                                   Updating
                                                                                                               Issues
                                                                                    wrong
                                                            is
                                             and
                      hit
   Paging
                                                    consider
                                             a
                                     one
                                                                            many
                                                                                                   TLB
                                                            the
                                                                                          switch
                                                                                    page
                                             hit
                      ratio
                              memory
                                                                     numbers)
                                                    TLB
                      to
                                                                                          may
                                                                            TLBs
                                                                     to
               improvement.
                                                                                                   tricky
                                                                                    table
                                             ratio
                                     memory
                                                                                                   if
                              access
                      98%
                                                    search
                                             of
                                                                                                   it
                                                            percentage
                                                                                                   is
                                                                                          requires
                                                                            support
                                                            of
                                                                     improve
                                                                                    entries.
                              time
                                                    time
                                             80%
                      gives
                              is
                                     reference
                                                                                                   full:
                                                    of
                                                                                          TLB
                                                            time
                              0.8
                                                            a
                                                                            process
                                                                                                   need
                              ×
                                                                                          flush
                                                    20ns,
                      effective
                                                                                                   to
                                     required
                                                            page
                                                                            tags
                              120
                                                                                          so
                                                                     performance.
                                     for
                              +
                      access
                                                                                          that
                                                            entry
                                                    memory
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                                                                                                   discard
                                     page
                                                            is
                              ×
                      time
                                                                                          next
                                                                            (sometimes
                      of
                              220
                                                    access
                                     table
                                                            found
                              =
                                                            in
                                                    time
                                                                                          process
                                                                                                   something.
                                                                            called
                      122ns
                                                    of
                                     lookup,
                      —
                                                            TLB
                              140ns.
                                     the
                                                                                          doesn’t
   49
                      only
                                                                            address
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