Re: kupdate & laptop's [patch for integration of mobile-update]
Zack Weinberg (zack@bitmover.com)
Sat, 14 Aug 1999 18:48:21 -0700
Richard Gooch wrote:
> Peter Englmaier writes:
> > I tried to deactivate everything, but even in single user mode and
> > no process or daemon running, I get disk I/O. Yes it stops after a
> > while, but a simple 'ls' triggers new activity even if all is in
> > cache already (ls finished and a second later the disk i/o happens).
> > Perhaps this is some timestamp business, and how can I hope to patch
> > every user land command to avoid it? With mobile-update you can
> > edit, compile, run programs without any disk i/o.
>
> There must be something wrong in your setup. I don't experience these
> problems. If a simple <ls> triggers a spin-up, then check to make sure
> you're mounting with the "noatime" flag. By default, a simple read of
> a file/directory will cause the inode access time to be updated, which
> in turn requires the disc to be written to.
Noatime helps but is not a panacea. Even with noatime set, an
opendir/readdir/closedir sequence will spin up the disk every time. I
have no idea why. I don't really mind ls spinning it up - if I'm
actually working on the machine, it's fine for the disk to be
running. I just want it off when the machine is idle, because it
generates a ridiculous amount of heat when it's spinning.
I'd like to see atime updates be recorded in memory but not flushed
back until the inode cache is shrunk, the fs is unmounted, or we need
to write back the inode for some other reason. Sort of like the
current handling of dtime in ext2. This should give the speed
improvement without losing the information.
zw
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