[laptop-mode] Enabling Laptop Mode Activate Pdflush Every 3-4 Seconds

[Casey McGinty]

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On Wed, May 27, 2009 at 1:33 AM, Bart Samwel <bart at samwel.tk> wrote:

>
> The thing is, laptop mode works as follows:
>
> - Detect disk activity -> activate!
> - Wait until disk activity stops for 2 seconds
> - Sync and deactivate!
>
> I'm getting the impression that this is caused by some kind of
> after-the-sync-finishes disk activity by the md drivers. Because then it
> works like this:
>
> - Detect disk activity -> activate!
> - Wait until disk activity stops for 2 seconds
> - Sync and deactivate
> - ...something in md is still writing to disk after the sync has returned
> - Detect disk activity -> activate!
>
> However, this is hard to detect without logging of sync boundaries and
> laptop mode activation / deactivation, and that's not in the kernel. :-/
> Do you compile your own kernels or do you run a stock kernel?
>
>
Thanks Bart,

The kernel is Stock from Ubuntu 9.04.

The interesting point is that there is zero disk activity when laptop mode
is *disable*. Even to the point that the RAID array will spindown after 5 or
10 minutes. When laptop mode is enabled (and this is the only change) the
drive lights are constantly flashing every few seconds. I have a separate
indicator lights on the 4 drives in my RAID array, and ALL the lights become
active.

How do you explain this? Even if there is are 100's of processes writing to
my other volumes, the large RAID array is usually idle as they are not part
of the standard Linux FS path.

Can you recommend any more tests that might test out the scenario above. For
example, is there a way to change the 2 second delay, to something longer?
Has anyone else verified that laptop-mode works with the RAID sub-system?

Thanks
Casey

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<br><br><div class=3D"gmail_quote">On Wed, May 27, 2009 at 1:33 AM, Bart Sa=
mwel <span dir=3D"ltr">&lt;<a href=3D"mailto:bart at samwel.tk">bart at samwel.tk=
</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_quote" style=3D"border=
-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-lef=
t: 1ex;">
<div class=3D"im">
<br>
</div>The thing is, laptop mode works as follows:<br>
<br>
- Detect disk activity -&gt; activate!<br>
- Wait until disk activity stops for 2 seconds<br>
- Sync and deactivate!<br>
<br>
I&#39;m getting the impression that this is caused by some kind of<br>
after-the-sync-finishes disk activity by the md drivers. Because then it<br=
>
works like this:<br>
<br>
- Detect disk activity -&gt; activate!<br>
- Wait until disk activity stops for 2 seconds<br>
- Sync and deactivate<br>
- ...something in md is still writing to disk after the sync has returned<b=
r>
- Detect disk activity -&gt; activate!<br>
<br>
However, this is hard to detect without logging of sync boundaries and<br>
laptop mode activation / deactivation, and that&#39;s not in the kernel. :-=
/<br>
Do you compile your own kernels or do you run a stock kernel?<br>
<br></blockquote></div><br>Thanks Bart,<br><br>The kernel is Stock from Ubu=
ntu 9.04.<br><br>The interesting point is that there is zero disk activity =
when laptop mode is *disable*. Even to the point that the RAID array will s=
pindown after 5 or 10 minutes. When laptop mode is enabled (and this is the=
 only change) the drive lights are constantly flashing every few seconds. I=
 have a separate indicator lights on the 4 drives in my RAID array, and ALL=
 the lights become active.<br>
<br>How do you explain this? Even if there is are 100&#39;s of processes wr=
iting to my other volumes, the large RAID array is usually idle as they are=
 not part of the standard Linux FS path.<br><br>Can you recommend any more =
tests that might test out the scenario above. For example, is there a way t=
o change the 2 second delay, to something longer? Has anyone else verified =
that laptop-mode works with the RAID sub-system?<br>
<br>Thanks<br>Casey<br>

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