Il giorno 10 set 2019, alle ore 18:08, Tejun Heo [off-list ref] ha scritto:

Hello, Michal.

On Tue, Sep 10, 2019 at 02:55:14PM +0200, Michal Koutný wrote:

quoted

This adds the generic io.weight attribute. How will this compose with
the weight from IO schedulers? (AFAIK, only BFQ allows proportional
control as of now. +CC Paolo.)

The two being enabled at the same time doesn't make sense, so we can
just switch over to bfq when bfq is selected as the iosched.  I asked
what Paolo wanted to do in terms of interface a couple times now but
didn't get an answer and he posted a patch which makes the two
controllers conflict, so....  Paolo, so it looks like you want to
rename all bfq files to drop the bfq prefix, right?

Yep, mainly because ... this is the solution you voted and you
yourself proposed [1] :)

[1] https://patchwork.kernel.org/patch/10988261/

 I can implement
the switching if so.

That would be perfect.

Thanks,
Paolo

quoted

I see this attributes are effectively per-cgroup per-device. Apparently,
one device should have only one weight across hierarchy. Would it make
sense to have io.bfq.weight and io.cost.weight with disjunctive devices?

It never makes sense to have both enabled, so I don't think that
interface makes sense.

quoted

quoted

+		.name = "cost.qos",
+		.flags = CFTYPE_ONLY_ON_ROOT,
[...]
+		.name = "cost.model",
+		.flags = CFTYPE_ONLY_ON_ROOT,

I'm concerned that these aren't true cgroup attributes. The root cgroup
would act as container for global configuration options. Wouldn't these
values better fit as (configurable) attributes of the respective
devices?

Initially, I put them under block device sysfs but it was too clumsy
with different config file formats and all.  I think it's better to
have global controller configs at the root cgroup.

quoted

Secondly, how is CFTYPE_ONLY_ON_ROOT supposed to be presented in cgroup
namespaces?

Not at all.  These are system-wide configs.  cgroup namespaces
shouldn't have anything which aren't in non-root cgroups.

Thanks.

-- 
tejun