Re: [PATCH v2] blk-cgroup: always display debug stats in io.stat

[Tejun Heo <tj@kernel.org>]

Hello, Breno.

On Wed, Mar 04, 2026 at 01:56:43AM -0800, Breno Leitao wrote:
> > Given that they haven't changed for a long time, maybe it's okay to expose
> > them by default, but why? This is something which can be toggled on easily
> > at any time.
> 
> My goal is to ship a kernel that exposes these detailed io stats by
> default, without requiring any runtime configuration. The stats should
> simply be available out of the box.

This is a pretty trivial patch to carry, right? Or just do it as a part of
boot system config?

> > What's the benefit of exposing these extra numbers which
> > probably don't mean much for most people?
> 
> My original plan was to introduce a Kconfig option for this. In v1 (about a
> month ago), Michal suggested removing the toggle entirely and always exposing
> the stats, which seemed reasonable to me and received no objections, so I
> went ahead with that approach.
> 
> To be clear: is your position that we should not support building a kernel
> that always exposes the detailed stats in io.stat?

As a debug option maybe but I'd prefer if vendors (including us) that want
to permanently enable these debug stats carried the patch in their trees.

I think that these are a bit too tied to the specifics of the current
implementation and it's not very difficult to imagine at least some of the
keys changing or getting dropped in the future, so I'm reluctant to export
them by default.

Thanks.

-- 
tejun