Re: [Jfs-discussion] Laptop mode

[Dave K. <sh...@au...>]

On Fri, 2004-04-30 at 15:35, Bart Samwel wrote:
> On Fri, 2004-04-30 at 22:25, Dave Kleikamp wrote:
> > All I meant by that is that if a thread were actively writing to jfs (or
> > creating, renaming, deleting files, etc.) that that activity may cause
> > older data & metadata to be written.  This is such an obvious statement,
> > I really didn't need to say it.
> 
> Yeah, but I still don't quite get it. :) Are you referring to the
> situation where there are too many pending changes and some older ones
> need to be flushed, because of a journal size limit or something like
> that?

Yes, it would take something creating a new transaction to initiate this
kind of I/O.

>  Or are we talking about when something is actually physically
> forcing some changes to disk (using something like fsync()), which might
> force older changes to disk because of ordering restrictions?

and Yes.  A synchronous operation like fsync would force all of the
dirty pages of the journal to be flushed.  The completion of the I/O to
the journal may initiate some other I/O as well, since inode and block
maps are updated after the transactions are committed to the journal.

> JFS seems to be behaving very well with Laptop Mode: I got over two
> minutes of silence until I gave up. Any of those other filesystems
> (ext3, ReiserFS, XFS) would have already given up after a couple of
> seconds. So, until I hear otherwise I'll assume laptop mode and JFS work
> just fine.

Great.  Thanks for the quick response.

Shaggy
-- 
David Kleikamp
IBM Linux Technology Center