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

[John Ogness]

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 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