finish_task_switch high in profiles in 2.6.7

[Yusuf Goolamabbas]

Hi, I have a fairly busy mailserver which also has a simple iptables
ruleset (blocking some IP's) running 2.6.7 with the deadline i/o
scheduler. vmstat was reporting that system time was around 80%. I did
the following

readprofile -r ; sleep 240 ; readprofile -n -m /boot/System.map-`uname
-r` | sort -rn -k 1,1 | head -22

 48036 total                                      0.2274
  9684 finish_task_switch                        80.0331
  6992 default_idle                             158.9091
  6335 __wake_up                                 87.9861
  5671 remove_wait_queue                         76.6351
  4150 add_wait_queue                            59.2857
  2459 sysenter_past_esp                         21.7611
  1304 find_get_page                             21.0323
  1160 __mod_timer                                4.1281
   938 do_gettimeofday                            5.0430
   756 del_timer_sync                             2.4787
   753 del_timer                                  7.1714
   599 handle_IRQ_event                           5.9900
   570 do_page_fault                              0.4612
   485 __do_softirq                               2.8529
   476 do_sigaction                               0.9136
   469 do_getitimer                               1.7055
   464 do_setitimer                               0.9768
   392 get_offset_tsc                            17.0435
   340 current_kernel_time                        4.9275
   293 in_group_p                                 2.4417
   272 eligible_child                             1.4093

On a 2.6.5 box with a similar workload, the profile is as follows

131202 total                                      0.3704
 42080 fget                                     667.9365
 12868 schedule                                   8.1084
 11231 default_idle                             255.2500
  9157 fput                                     436.0476
  6642 remove_wait_queue                         89.7568
  6076 __wake_up                                 93.4769
  5056 page_remove_rmap                          13.4111
  4144 add_wait_queue                            59.2000
  2255 fget_light                                17.4806
  2176 sysenter_past_esp                         19.2566
  1271 kfree                                     11.6606
  1148 kmem_cache_alloc                          14.9091
   934 __kmalloc                                  6.6714
   890 __mod_timer                                3.1673
   768 del_timer_sync                             2.9538
   717 buffered_rmqueue                           1.5621
   715 kmem_cache_free                            8.2184
   613 free_hot_cold_page                         2.4618
   612 del_timer                                  5.8286
   588 __find_get_block                           3.0466
   588 do_page_fault                              0.4757

I am trying to determine where the system time is going and don't have
much zen to begin with. Any assistance would be appreciated ?

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/