Performance of -mm2 and -mm4

["Martin J. Bligh" <mbligh@aracnet.com>]

Kernbench: (make -j vmlinux, maximal tasks)
                              Elapsed      System        User         CPU
                  2.6.8.1       43.90       87.76      572.94     1505.67
              2.6.8.1-mm1       44.26       87.71      574.73     1496.33
              2.6.8.1-mm2       44.27       90.27      574.84     1502.33
              2.6.8.1-mm4       45.87       97.60      595.23     1510.00

mm2 seems to take slightly (but consistently) more systime than mm1, and
mm4 is significantly worse still ;-(

diffprofile from mm1 to mm2:

      5469  32170.6% find_get_page
       785    13.0% __d_lookup
       476     0.4% total
       128    21.9% generic_file_open
        93    22.5% __alloc_pages
        62    26.1% file_ra_state_init
        58     0.0% put_page
        54     9.9% dput
...
       -51    -2.8% finish_task_switch
       -55    -4.3% __wake_up
       -67    -6.6% file_move
      -128    -1.7% __copy_to_user_ll
      -156    -1.1% do_anonymous_page
     -2189    -4.7% default_idle
     -3632  -100.0% find_trylock_page

and -mm1 to -mm4

      5841  34358.8% find_get_page
      5394     4.0% total
      1459    24.2% __d_lookup
       740     9.2% __copy_from_user_ll
       718     9.5% __copy_to_user_ll
       304    24.0% __wake_up
       253    20.2% free_hot_cold_page
       248    19.8% atomic_dec_and_lock
       229    42.2% dput
       228    13.7% path_lookup
       226    43.0% Letext
       202    34.6% generic_file_open
       197    23.6% pte_alloc_one
       194    77.0% pgd_ctor
       180    22.6% kmem_cache_free
       173     6.5% zap_pte_range
       170     9.2% buffered_rmqueue
       146    16.1% in_group_p
       123    22.3% __fput
...
       -56   -23.5% file_ra_state_init
       -72   -31.7% page_add_anon_rmap
      -104    -5.6% finish_task_switch
      -124    -0.9% do_anonymous_page
     -3633  -100.0% find_trylock_page
     -4636   -10.0% default_idle

The -mm4 looks more like sched stuff to me (copy_to/from_user, etc),
but the -mm2 stuff looks like something else. Buggered if I know what.
-mm3 didn't compile cleanly, so I didn't bother, but I prob can if you
like.

m.