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Re: saving battery by syncing less

> Hoi one and all,
> I just recently got a Dell Latitude LS, which makes me subscribe to this list.
> I am running potato on it, and Kernel 2.2.16. :-)))
I don't believe I'd seen a reply to this, so here goes.  We've had considerable
threads on this.  I did a decent attempt at summarizing the suggestions a bit 

> Situation:
>    The Battery-Savings-Howto mentions something about starting bdflush/update
>    with a less frequent rate. My laptop apparently does some HD activity
>    everytime I sync it. (I can her it scratch) As the kupdate does syncing
>    regularly, this make my HD never spin down to save battery power.
>    With older kernels (2.0.xx) update did this jobs as a separate program
>    where one could supply it with command line params telling it to do it
>    not so often. With newer kernels, this is no longer the case, as kupdate
>    is directly built into the kernel.
You are correct, bdflush and updated used to both be external applications.
For 2.0.x versions with them, the debian package 'mobile-update' replaces
them with kinder versions.

> Question:
>    How can I tell the kernel to sync less frequently?
>    I did not find any clue neither in the kernel documentation nor in
>    the docu of the old update program. I could not even find anything
>    called update or bdflush in the kernel sources, that would give me
>    a clue.
I have determined through experimentation that 'noflushd' seems to be the
most part of a correct answer here.  My tests have it working well on kernels
2.2.12 through 2.2.16 (a 2.2.16 custom kernel, I have to note)

It however will only let you spin down for about 20 minutes if you do not
also adjust /etc/init.d/sysklogd to add the "-m 0" switch to syslog.  The
darn thing insists on adding a (normally 20 minute) timemark to the log.
I suppose you can also abuse this to insist on a sync by increasing it 
mightily, say, to 60 minutes, or 2/3 of your expectable battery life, or
some other value that suits your fancy.

I also significantly reduced the default things that log at all, on my
personal stuff. That's options in /etc/syslog.conf - some things I moved to
only logging on /dev/tty12, others, I use -filename to tell them they don't
*have* to sync these.   

btw, if anybody has particular comments about the kind of logged data that 
are more trouble to generate than their disk space is worth (other than time 
marks) I'd like to hear 'em :)  My personal preferences: cron logs are mostly
useless if you're not an open server and you've got nice crunchy ipchains.
kernel log is kind of nice to sync, it's not very noisy and if it is, there
might actually -be- a big problem. Well, unless you compile a deliberately
noisy kernel anyway... my thoughts are still out on maillogs.

> Cheers, Etienne


-* Heather Stern * star@ many places *-

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