Messages in this thread | | | Date | Mon, 23 May 2011 10:22:02 +0200 (CEST) | From | Jesper Juhl <> | Subject | Re: [rfc] Ignore Fsync Calls in Laptop_Mode |
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On Fri, 20 May 2011, D. Jansen wrote:
> On Fri, May 20, 2011 at 5:28 PM, <Valdis.Kletnieks@vt.edu> wrote: > > On Thu, 19 May 2011 15:34:46 +0200, Dennis Jansen said: > > > >> Testing: > >> I've been using this workaround on my netbook for over six months now. > >> It works as expected for me with all software in a Ubuntu 9.10 > >> environment and saves me at least 0.5 Watt or roughly 10 % battery > >> time - without destroying my hard disk. I have seen no negative side > >> effects. > > > > How much destructive testing did you do? In the 6 months, how many times did > > the system crash (or had the battery pulled out, or whatever) while large > > amounts of data were still pending after apps thought they were fsync'ed? How > > much crash testing was done against apps that use fsync for ordering or > > correctness reasons? > > I don't see the point in verifying the obvious. Of course applications > that rely on fsync will lose data. > The real problem comes with ordering correctness, which could actually > _destroy previous data_ as well. > In my scenario (office applications, browsing) I have not hit such a problem. > > Does anyone know a Linux app that actually does rely on ordering > correctness? Is that one which is used on a laptop? In laptop mode? > (-> when on battery?) Because so far the discussion seems to be > running in circles around Alan's mailer daemon. I would just shut that > down on enabling laptop mode. Problem solved. But I don't run that on > my laptop, anyway, esp. in laptop mode. I wonder who would, too. >
PostgreSQL's Write Ahead Log (WAL) would be one such example as far as I can see ( http://www.westnet.com/~gsmith/content/postgresql/TuningPGWAL.htm ). And yes, people run that on laptops while on battery (I know that for a fact since I do that myself).
-- Jesper Juhl <jj@chaosbits.net> http://www.chaosbits.net/ Don't top-post http://www.catb.org/jargon/html/T/top-post.html Plain text mails only, please.
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