Re: [PATCH v4 1/1] Documentation: real-time: Add kernel configuration guide

[Sebastian Andrzej Siewior]

On 2026-07-21 17:58:00 [+0206], John Ogness wrote:
> On 2026-07-21, Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote:
> > On 2026-07-21 10:48:06 [-0400], Steven Rostedt wrote:
> >> On Tue, 21 Jul 2026 16:36:06 +0200
> >> Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote:
> >> 
> >>>> Unfortunately, debugfs is needed to configure the fair deadline server:
> >>>> 
> >>>>     /sys/kernel/debug/sched/fair_server/cpu*/runtime  
> >>> 
> >>> So drop the reference to it. It is not "bad" to have it enabled. It is
> >> 
> >> I believe that some distros feel that it is bad to enable because there's
> >> no real auditing of its interface. Although, it is now only accessible by
> >> root.
> >
> > Yeah. Either way, there shouldn't be anything real-time specific that
> > requires the user have it enabled or disabled.
> 
> The fair deadline server is certainly real-time specific. It is the
> new/additional RT throttling mechanism. Generally speaking, RT systems
> will want to disable it or at least reduce the 50ms default.
>
> This document is not about runtime settings, but if debugfs is not
> enabled, the user will have no way to configure the fair deadline server
> at runtime.

I would suggest to delegate it to the proper section. Also, maybe we get
a proper interface outside of debugfs.

> I am OK if it is completely dropped from this document. But if there are
> distros that think it is bad, it might be worth mentioning that this
> config is important (if not critical) for real-time systems.
> 
> John

Sebastian