Subject: Re: Who's accessing my disk?
To: Ken Hornstein <email@example.com>
From: Jukka Marin <firstname.lastname@example.org>
Date: 02/08/1999 11:31:03
On Mon, Feb 08, 1999 at 03:08:20AM -0500, Ken Hornstein wrote:
> >Yes, I know what update is and why it does what it does. What I didn't know
> >was why anything was "flushed to disk" when no data were being written to any
> >file. The answer is that sync() updates the disk superblock timestamps
> >even when no buffers are actually flushed to disk. So, as far as I
> >understand, using async mount is currently the only way to keep the disk
> Dambit, that's _not_ the behavior I saw when I was working on this.
Maybe I'm doing something wrong, then? I'm running the 990131 snapshot.
Here's my fstab:
/dev/wd0a / ffs rw,noatime,nodevmtime 1 1
/dev/wd0b none swap sw 0 0
/dev/wd0e /usr ffs rw,noatime 1 2
/dev/wd0f /var ffs rw,noatime 1 2
/dev/wd0b /tmp mfs rw,nosuid,-N,-s=65536
/dev/wd0g /home ffs rw 1 2
/dev/wd0h /dos msdos rw,noauto 1 2
/kern /kern kernfs rw
And then I manually run "atactl wd0 setidle 5" and the disk stops after
a while - but it starts again within 30 seconds, stops, starts, stops..
I have kdm running, but nobody has logged on. I don't think there would
be any processes writing to disk all the time.
> The superblock timestamp only got updated when something else got
> updated. From my memory (and a quick glance at the code), yes,
> that's right ... the superblock only gets written back when
> fs->fs_fmod is non-zero.
Then what is it? :-)
> What I did to debug this was to print out the inode number of every
> file that gets updated. You can put this code in /sys/ufs/ffs/ffs_vfsops.c
> in ffs_sync(). Of course, this will make your kernel log file grow
> :-) When you get the inode number (the appropriate filesystem will
> probably be useful as well) then you can use find (-inum) to find
> the right file, and that should get you going in the right direction.
Hmm.. I'll try killing xdm and see if that helps.. a bit annoying because
top doesn't work and ps seems to print garbage as well.. ;)
> You can also use -async, but that's mainly a big help when doing
> directory updates.
I don't like -async on my laptop (afraid of messing up the disk and
making the system unusable when I'm far away from the backups..