Re: dirty_writeback_centisecs didn't stop idle writes - Portable

This is a discussion on Re: dirty_writeback_centisecs didn't stop idle writes - Portable ; Say, even in the idlest of nights, the disk was still going kerchunk every 5 seconds. No it's not broke. Does this mean ext3 just writes zero bytes for the heck of it when there's nothing to write? How can ...

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Thread: Re: dirty_writeback_centisecs didn't stop idle writes

  1. Re: dirty_writeback_centisecs didn't stop idle writes

    Say, even in the idlest of nights, the disk was still going kerchunk
    every 5 seconds. No it's not broke. Does this mean ext3 just writes
    zero bytes for the heck of it when there's nothing to write? How can
    one snoop on what it really does or doesn't write each commit time?

    OK, I'll try mount -o commit=300 next time.

  2. Re: dirty_writeback_centisecs didn't stop idle writes

    On Fri, 18 Nov 2005 06:33:26 +0800, Dan Jacobson staggered into the
    Black Sun and said:

    When you post a reply to a message on Usenet, *don't* start a new
    thread. Just reply/followup to the last message in the already-existing
    thread. And include context when you post. Context restored:

    > Dances With Crows wrote:
    >>Dan Jacobson wrote:
    >>> I notice my IBM Thinkpad r50e though idle still makes a faint hard
    >>> disk ding-dong sound every 5 seconds

    >>By default, ext3 commits journal data every 5 seconds. Mount the
    >>filesystem with "commit=NN" where NN is the number of seconds you wish
    >>to elapse between commits. You'll probably have to edit your
    >>/etc/fstab for this to be permanent.


    > Say, even in the idlest of nights, the disk was still going kerchunk
    > every 5 seconds. Does this mean ext3 just writes zero bytes for the
    > heck of it when there's nothing to write?


    How do you know there was nothing to write? Remember that atimes will
    be getting updated if files on the ext3 filesystems are being accessed
    and you didn't mount the filesystems with noatime. Remember the system
    logger is always active and typically writes "--MARK--" once every 20
    minutes if nothing else happened.

    > How can one snoop on what it really does or doesn't write each commit
    > time?


    Possibly by building ext3 with JBD debugging enabled, then doing "echo
    'N' > /proc/sys/fs/jbd-debug" where N is between 1 and 5. If that
    doesn't help, by putting more printk()s in the relevant part of the ext3
    filesystem code. I think the place to start would be
    ext3_commit_super() , but I'm not a filesystem guru.

    --
    Matt G|There is no Darkness in Eternity/But only Light too dim for us to see
    Brainbench MVP for Linux Admin / mail: TRAP + SPAN don't belong
    http://www.brainbench.com / "He is a rhythmic movement of the
    -----------------------------/ penguins, is Tux." --MegaHAL

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