Re: 2.6.5-rc3-mm4

[Andrew Morton <akpm@osdl.org>]

markw@osdl.org wrote:
>
> I reran DBT-2 to with ext2 and ext3 (in case you were still interested)
>  on my 4-way Xeon system with 60+ drives:
>  	http://developer.osdl.org/markw/fs/dbt2_project_results.html
> 
>  Aside from the from the drop you're already aware of since 2.6.3, it
>  looks like DBT-2 takes another smaller hit after 2.6.5-rc3-mm2.  Here's
>  a brief summary from the link above:

The profile is interesting:

3671973 poll_idle                                63309.8793
 77750 __copy_from_user_ll                      637.2951
 64788 generic_unplug_device                    487.1278
 62968 DAC960_LP_InterruptHandler               336.7273
 53908 finish_task_switch                       361.7987
 52947 __copy_to_user_ll                        441.2250
 29419 dm_table_unplug_all                      439.0896
 25947 __make_request                            17.9938
 18564 dm_table_any_congested                   199.6129
 13785 update_queue                             104.4318
 13498 try_to_wake_up                            20.3590
 12736 __wake_up                                114.7387
 12560 kmem_cache_alloc                         163.1169
 12221 .text.lock.sched                          40.7367

- There's a ton of idle time there.

- The CPU scheduler is hurting.  Nick and Ingo are patching up a storm to
  fix a similar problem which Jeremy Higdon is observing at 200,000
  IOs/sec.  This will get better.

- That 60-disk LVM array is costing us in the new unplug and congestion
  code.  Jens, didn't you have a tune-up for that in the works?

- I'm surprised that you didn't see big gains from ext3-fsync-speedup,
  even though it appears that the test uses fdatasync().