On Mon, 2017-01-16 at 20:19 -0500, Matthew Miller wrote:
On Mon, Jan 16, 2017 at 06:07:42PM -0600, Michael Catanzaro wrote:
> It includes a couple recommendations:
> * We should restore systemd-readahead to speed boot time by ~30%
> users without SSDs. Endless has a downstream patch for this. Or we
> could use Ubuntu's readahead utility.
Has Endless done benchmarks? I'd hate to renable it based mainly on
I don't know. I think their benchmarks would not be super relevant to
us anyway, since they are targeting extremely low-end hardware; I would
be unsurprised if readahead is far more important for Endless than it
is for Fedora.
But this reviewer has taken measurements (the basis for that 30%
number). They're at the bottom of his Fedora 25 review. They are not
super scientific, because they are comparing Fedora to Ubuntu, but this
same reviewer also reviewed Fedora 22 a while back with and without
readahead. His boot took 38 seconds without readahead and 28 seconds
with readahead. It is an anecdote, since it's only tested on one single
computer, but the difference is quite major:
Same point about benchmarks applies here, although it's a lot
to experiment with and the consequences easily reversed. FWIW, RHEL 7
defaults to deadline on all devices except SATA disks, which default
CFQ. And on virtual disks, you get no IO scheduling at all, which
sense and makes this irrelevant in those cases.
Very interesting that our behavior is different from RHEL!