lkml.org 
[lkml]   [2004]   [Mar]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: 2.6.4-mm2
On Thu, Mar 18 2004, Andrew Morton wrote:
> > Comparing one pair of readprofile results, I find it curious that
> > dm_table_unplug_all and dm_table_any_congested show up near the top of a
> > 2.6.4-mm2 profile when they haven't shown up before in 2.6.3.
>
> 14015190 poll_idle 241641.2069
> 175162 generic_unplug_device 1317.0075
> 165480 __copy_from_user_ll 1272.9231
> 161151 __copy_to_user_ll 1342.9250
> 152106 schedule 85.0705
> 142395 DAC960_LP_InterruptHandler 761.4706
> 113677 dm_table_unplug_all 1386.3049
> 65420 __make_request 45.5571
> 64832 dm_table_any_congested 697.1183
> 37913 try_to_wake_up 32.2939
>
> That's broken. How many disks are involve in the DM stack?
>
> The relevant code was reworked subsequent to 2.6.4-mm2. Maybe we fixed
> this, but I cannot immediately explain what you're seeing here.

Ugh that looks really bad, I wonder how it could possibly ever be this
bad. Mark, please do do a run with 2.6.5-rc1-mm2, I'd very much like to
see the profile there. If things get this bad, I need to think some more
about how to best handle the 'when to invoke request_fn on unplug calls'
logic again.

Actually, please also do a run with 2.6.5-rc1-mm2 + inlined patch. For
non-stacked dm on dm it should work and could make a lot of difference
for you.

--- drivers/block/ll_rw_blk.c~ 2004-03-18 20:26:17.088531084 +0100
+++ drivers/block/ll_rw_blk.c 2004-03-18 20:26:44.773554953 +0100
@@ -1134,11 +1134,8 @@
if (test_bit(QUEUE_FLAG_STOPPED, &q->queue_flags))
return;

- /*
- * always call down, since we can race now with setting the plugged
- * bit outside of the queue lock
- */
- blk_remove_plug(q);
+ if (!blk_remove_plug(q))
+ return;

/*
* was plugged, fire request_fn if queue has stuff to do
--
Jens Axboe

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

\
 
 \ /
  Last update: 2005-03-22 14:01    [from the cache]
©2003-2011 Jasper Spaans