xfsaild causing 30+ wakeups/s on an idle system since 2.6.25-rcX

["Török Edwin" <edwintorok@gmail.com>]

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Hi,

xfsaild is causing many wakeups, a quick investigation shows
xfsaild_push is always
returning 30 msecs timeout value.

This is on an idle system, running only gnome, and gnome-terminal.

I suggest changing the timeout logic in xfsaild to be more power
consumption friendly.

See below my original report to the powerTOP mailing list.

Best regards,
--Edwin

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From: Arjan van de Ven <arjan@linux.intel.com>
To: "Török Edwin" <edwintorok@gmail.com>
Cc: power@bughost.org
Subject: Re: new offender in 2.6.25-git: xfsaild
Date: Sun, 17 Feb 2008 08:09:06 -0800
Message-ID: <47B85C22.3070504@linux.intel.com>

Török Edwin wrote:
> Török Edwin wrote:
>> Hi,
>>
>> On latest -git of 2.6.25 I am getting lots of wakeups from xfsaild.
>>   23.5% ( 33.3)           xfsaild : schedule_timeout (process_timeout)
>>   
> 
> [Should I Cc: xfs mailing list / lkml on this?]
> 
> The problem seems to be with the timeout logic in xfsaild_push, which
> can return 3 timeout values (msecs): 1000, 10, 20, 30.
> I inserted a marker and attached a probe function, schedule_timeout
> always got called with 9 jiffies (which is 30 msecs, I have HZ=300).
> 
> Changing xfs_trans_ail.c:270 from "tout += 20" to "tout = 1000", made
> xfsaild only do 1 wakeup/s instead of 33!
> 
> For some reason xfs_aild always thinks it has work (I/O) to do, and
> never chooses the 1000 msec sleep value.
> 

sounds like an XFS bug... worth reporting to the xfs/lkml folks for sure.