[laptop-mode] Tweak laptop-mode for SSD-disk

[Bart Samwel]

Hi rancor,

rancor wrote:
> I'm using Xubuntu 8.04 and it's default installation of laptop-mode on a Acer Aspire One that has a 8Gb ssd-disk.
> 
> I'm trying to figure out all possible ways of minor the wear of the ssd and because the disk is smal the wear increase and it's theirfor important to write as less as possible to the disk.
> 
> I think it may be intersting to change the default configuration.
> 
> I just started on this track. I have figured this out at this time.
> 
> CONTROL_NOATIME=0 -> 1
> Reference: http://kerneltrap.org/node/14148

Yes, you should use CONTROL_NOATIME=1. The default configuration is to 
use relatime, but to reduce the number of writes even more you should 
consider setting USE_RELATIME=0, which means that the "noatime" option 
is used instead. A small number of programs (most notably mutt) have 
problems with this option, but I haven't seen much problems with it myself.

> I'm thinking of the *_HD_IDLE_TIMEOUT_SECOUNDS, *_HD_WRITECACHE and how the pdflush writes from memory to disk to make it only write after the dirty_exprire-timouts.

The idle timeout and write cache settings shouldn't help you much with 
an SSD. Writecache is a setting for normal HDs which allows the drive to 
reorder writes so that performance is improved, it does not cause any 
reduction in writes and it is not useful for SSDs. The idle timeout is 
also for HDs, to spin them down. I doubt if that has any effect at all. 
No, better stick with the CONTROL_NOATIME=1 and the normal behaviour 
(write all pending changes every 10 minutes). That will get you the 
least number of writes.

Cheers,
Bart