Matthew Miller píše v Po 16. 01. 2017 v 20:19 -0500:
On Mon, Jan 16, 2017 at 06:07:42PM -0600, Michael Catanzaro wrote:
>
http://www.hecticgeek.com/2016/12/fedora-25-review/
> It includes a couple recommendations:
> * We should restore systemd-readahead to speed boot time by ~30%
> for
> 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
anecdotes. If it turns out to be worthwhile, it'd be nice to work
with
Endless to get the feature back upstream in systemd - if I remember
right, one of the points at its removal was that the main developers
didn't have the spinning-disk hardware to benefit from it and that no
one who cared stepped up. If it turns out that there _are_ people who
care, upstream seems like the right home.
> * We should switch from CFQ to deadline I/O scheduler (which
> Ubuntu
> has been using for years) for subjective massive responsiveness
> improvements when the system is under load
Same point about benchmarks applies here, although it's a lot less
work
to experiment with and the consequences easily reversed. FWIW, RHEL 7
defaults to deadline on all devices except SATA disks, which default
to
CFQ. And on virtual disks, you get no IO scheduling at all, which
makes
sense and makes this irrelevant in those cases
I briefly spoke with Jiri Hladky, the manager of the FS perf team in
Red Hat, and he says that deadline is clearly better for SSD. Results
for rotating disks are mixed, but he'd still prefer deadline there,
too. He can provide more detailed info if we need it.
Jiri