readahead_early.

[Dave Jones]

On Mon, Oct 08, 2007 at 03:08:17PM +0200, Karel Zak wrote:
 > On Fri, Oct 05, 2007 at 04:02:21PM -0400, Dave Jones wrote:
 > > Right now we're running readahead early way too late.
 > > At a time when we've just sat doing no IO at all for 10
 > > seconds whilst (amongst other things) we waited for a
 > > DHCP lease.   We're also running it at a time when
 > > we're competing for disk bandwidth with other processes.
 > > The result is that disabling the service completely shows
 > > no change in boot time at all.
 > > http://www.codemonkey.org.uk/junk/bootchart-before.png
 > > 
 > > Moving the readahead_early service to start really early
 > > wins back 4 seconds of boot up time.
 > > http://www.codemonkey.org.uk/junk/bootchart-after.png
 > 
 >  Please, define "really early".

I moved it to S01
 
 >  results (readahead on/off):
 > 
 >  http://people.redhat.com/kzak/readahead/f7-on.png
 >  http://people.redhat.com/kzak/readahead/f7-off.png
 > 
 >  .. so nothing useful :-(
 > 
 > > Any reason not to change this for F8 ?
 > 
 >  I don't believe that readahead is able to really improve Fedora boot
 >  time.
 
So over the weekend I reinstalled that test box with test3, and
made the same change to readahead.  This time it didn't make
any difference at all, so I'm inclined to believe you.

Eric Sandeen noted that it actually *slows down* his boot too,
so perhaps switching it off is the best plan.

	Dave

-- 
http://www.codemonkey.org.uk