BTRFS in laptop-mode

BTRFS in laptop-mode

[Adam Ryczkowski]

Welcome,

What are perspectives on BTRFS complying with laptop-mode and stop 
writing to disk every 30 sec?

The thread was asked several years before 
(http://mailman.samwel.tk/pipermail/laptop-mode/2012-February/000520.html), 
but time went by and maybe the situation became a little more on the 
bright side...? With kernel 3.8.11 I can still see with lm-profiler a 
lot of "btrfs-transacti" and ""btrfs-submit-1" events, roughly once 
every 30 sec.

Is there any tunable switch, that can delay such writes to, say, 15 
minutes, or better yet: until the disk started spinning anyway?

-- 

Adam Ryczkowski
+48505919892 <callto:+48505919892>
Skype:sisteczko <skype:sisteczko>

Re: BTRFS in laptop-mode

[David Sterba]

On Tue, May 14, 2013 at 10:32:43AM +0200, Adam Ryczkowski wrote:
> What are perspectives on BTRFS complying with laptop-mode and stop writing
> to disk every 30 sec?

> Is there any tunable switch, that can delay such writes to, say, 15 minutes,
> or better yet: until the disk started spinning anyway?

30 seconds is the regular transaction commit interval. Tweaking the
value is easy (via a mount option to make it clearly visible):

http://lxr.free-electrons.com/source/fs/btrfs/disk-io.c#L1691

but has implications about data safety in case of a long delay in
combination with a crash.


david