adventures in booting

[Colin Walters]

On Thu, 2004-12-02 at 12:40 -0500, David Zeuthen wrote:

> I'm almost positive it requires kernel changes to do this the right way;
> one naive idea is to have a userspace daemon, capturing what blocks are
> read when (kernel tells this daemon using the kernel events layer). This
> would run in the first three minutes on each and every boot. When the
> system is idle (and only when running on AC power!) another daemon
> rearranges blocks on the disk. What blocks to rearrange could be the
> result of a computation involving several three-minute result sets.

Rearranging sounds complex and dangerous, since it requires deep
integration with the filesystem.  The online resizing took quite a long
time to appear and that is conceptually much simpler.  Why not do it on
the block device layer (without knowledge of the filesystem) and just
copy those blocks to a reserved area of the block device?  Disks are
big, duplicating say 100MB for this purpose wouldn't be bad.  We would
need to ensure that mkfs.ext3 would leave enough space for this though
(and probably whatever does the copying would have to make sure that the
filesystem wasn't in the way; perhaps an ext flag).