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    SubjectRe: [rfc] Ignore Fsync Calls in Laptop_Mode
    On Fri, May 20, 2011 at 06:40:49PM +0200, 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.

    how about making fsync block until the harddisk spins up ?
    this would also enable you to detect these apps you wouldnt be using in
    laptop mode anyways ?


    --
    torben Hohn
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