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Date: Tue, 31 May 2011 15:47:15 +0200 From: "D. Jansen" <d.g.jansen@...glemail.com> To: "Ted Ts'o" <tytso@....edu>, "D. Jansen" <d.g.jansen@...glemail.com>, david@...g.hm, Oliver Neukum <oneukum@...e.de>, akpm@...ux-foundation.org, linux-kernel@...r.kernel.org, Dave Chinner <david@...morbit.com>, njs@...ox.com, bart@...wel.tk Subject: Re: [rfc] Ignore Fsync Calls in Laptop_Mode On Tue, May 31, 2011 at 4:03 AM, Ted Ts'o <tytso@....edu> wrote: > On Mon, May 30, 2011 at 11:24:03PM +0200, D. Jansen wrote: >> > do you really have so many fsync's going on that the disk spins up so much >> > that you would gain 10-20% battery life? >> >> Yes. Every autosave in LibreOffice triggers one. And I want autosave, >> but I want them in memory, not on disk. > > What on *heck* good does an autosave to memory do? Are you afraid > your X server is going to go poof, or OpenOffice is going to crash on > you? Unfortunately, yes. This happens to me regularly, e.g. roughly every 10th resume. It's a poulsbo system. ;) Another reason is a Java extension that makes it crash happy. (Please don't tell me now that the real fix is to fix poulsbo...) >I can't remember the last time this has happened to me. It's > typically a system crash or a power loss that causes me to lose an > OpenOffice session. Well, good for you! Power loss didn't ever occur to me on the other hand, at least not on my netbook. >> > and what makes you think the extra spin-ups from fsyncs will cause your hard >> > drive to fail significantly earlier? (if you have a hard drive with a >> > limited number of spin-up cycles, you probably don't want to use laptop mode >> > at all) >> >> Experience, see above. Also, this is well described behavior. All hard >> disks are only designed to last a certain number of head loads and >> unloads. Spinning up and down even less. > > Modern laptop drives are designed for 600,000 to a million head loads > and unloads. Open Office by default autosaves once every 15 minutes. > So if you leave your system running (on battery?!?) 24x7, with open > office open all that time, even with HDD which is only rated for 600k > load cycles, that's 4.5 years. Yeah, exactly what I had thought -- enabling laptop mode for the first time. After the hard disk started to show more read errors and almost crashed so I had to exchange it, I reconsidered. I wish specifications would be more in conformity with reality... Good thing I watch my smart log and caught it in time to avoid data loss. Though I do have a solid backup routine to avoid serious issues. > And of course, normally such a system > is powered all the time, and the hard drive shouldn't be spinning down > if you're on the AC mains. Well, I use my netbook on the go mostly. I guess we just have different habits. > > The real fix is that applications need to be fixed to be less > write-happy. Firefox example, used to request a transactional update > to a sqllite database on every web click. Laptop mode isn't the right > place to fix this, since if you try to stop the writes from hitting > the disk, you'll still end up burning memory that can't be released > until the data is written to disk. (...) That is another fix that everybody can benefit from. And another reason to provide barrier support for user space. (We have a new trojan horse!) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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