Re: 2.6.5-rc3-mm4

Andrew Morton
2004-04-02T19:56:13Z

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().