xfsaild centisecs /proc wakeup control?

xfsaild centisecs /proc wakeup control?

[Linda A. Walsh]

I was looking at powertop again recently, and noticed xfsbufd and xfsaild at the top
of the wakeup list. 
xfsbufd can be tuned with /proc/sys/fs/xfs/xfsbufd_centisecs along with 3 other
time-related tunables.  However, I don't see one for xfsaild.  Is that an oversight?

Re: xfsaild centisecs /proc wakeup control?

[Eric Sandeen]

Linda A. Walsh wrote:
> I was looking at powertop again recently, and noticed xfsbufd and xfsaild at the top
> of the wakeup list. 
> xfsbufd can be tuned with /proc/sys/fs/xfs/xfsbufd_centisecs along with 3 other
> time-related tunables.  However, I don't see one for xfsaild.  Is that an oversight?


On what kernel?

As far as the wakeups go, I thought this was fixed; see for example:
TAKE 977545 - xfsaild causing too many wakeups

on 2.6.27-rc8 with xfs mounted, and powertop 1.9, I don't see xfs up
very high at all:

Top causes for wakeups:
  29.4% ( 15.0)       <interrupt> : pata_sil680
   9.4% (  4.8)       <interrupt> : eth0
   7.8% (  4.0)            iscsid : __mod_timer (process_timeout)

...

   2.0% (  1.0)           xfsbufd : __mod_timer (process_timeout)
   2.0% (  1.0)           xfsaild : __mod_timer (process_timeout)


-Eric

Re: xfsaild centisecs /proc wakeup control?

[Dave Chinner]

On Wed, Oct 08, 2008 at 12:44:41PM -0700, Linda A. Walsh wrote:
> I was looking at powertop again recently, and noticed xfsbufd and
> xfsaild at the top of the wakeup list. xfsbufd can be tuned with
> /proc/sys/fs/xfs/xfsbufd_centisecs along with 3 other time-related
> tunables.  However, I don't see one for xfsaild.  Is that an
> oversight?

No. The xfsaild is currently operating with watchdog functionality
to catch AIL push stalls due to a know problem that this new patch:

http://oss.sgi.com/archives/xfs/2008-10/msg00119.html

fixes.

After this has been included for a while (say a release), I
plan to remove the watchdog feature of the xfsaild so the
once-per-second-per-XFS-filesystem wakeup will go away then.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

Re: xfsaild centisecs /proc wakeup control?

[Linda Walsh]

Eric Sandeen wrote:
> On what kernel?
2.6.26.0 (haven't rebooted to 2.6.26.5 yet)
> As far as the wakeups go, I thought this was fixed; see for example:
> TAKE 977545 - xfsaild causing too many wakeups
---
   It may  be fixed in a newer kernel...(referring to David's later comment)..

Just looked at it with powertop 1.10:


Wakeups-from-idle per second :  7.1     interval: 10.0s

Top causes for wakeups:
  42.9% (  6.0)           xfsaild : schedule_timeout (process_timeout)
  14.3% (  2.0)     <kernel core> : clocksource_register (clocksource_watchdog)
   8.6% (  1.2)           xfsbufd : schedule_timeout (process_timeout)
   7.1% (  1.0)                ip : tg3_open (tg3_timer)