Re: should readahead allow generic paths?

[Eric Sandeen <sandeen redhat com>]

Tony Nelson wrote:

> In any case, readahead does not improve boot time, and unless you can show
> how to make readahead improve boot time, there is unlikely to be any work
> done on making it keep reading all the files after updates.  It doesn't
> make booting any slower if readahead can't find its files, or any faster if
> it can.

Well, actually I don't quite agree (see also my "boot-time / readahead
investigations" thread)

with stock readahead (0:59):
http://sandeen.net/fedora_boot/bootchart-stockreadahead-noselinux.png
http://sandeen.net/fedora_boot/seekwatcher-stockreadahead-noselinux.png

without readahead (0:49):
http://sandeen.net/fedora_boot/bootchart-noreadahead-noselinux.png
http://sandeen.net/fedora_boot/seekwatcher-noreadahead-noselinux.png

with tweaked readahead (updated/sorted lists, run earlier) (0:44):
http://sandeen.net/fedora_boot/bootchart-fixedreadahead-noselinux.png
http://sandeen.net/fedora_boot/seekwatcher-fixedreadahead-noselinux.png

so, it's a small win for me.  The approach still feels a bit inelegant
to me, but it does seem to save a bit if it's done properly.  But from
above, if it's done wrong, it hurts a lot more than it helps.

Tossing a default list out there and hoping for the best probably won't
work, at any rate.

-Eric