linux-kernel - Re: [PATCH] sched_ext: Provide a sysfs enable

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Message-ID: <20240923160007.GA313849@pauld.westford.csb>
Date: Mon, 23 Sep 2024 12:00:07 -0400
From: Phil Auld <pauld@...hat.com>
To: Tejun Heo <tj@...nel.org>
Cc: andrea.righi@...ux.dev, David Vernet <void@...ifault.com>,
	Giovanni Gherdovich <giovanni.gherdovich@...e.com>,
	Kleber Sacilotto de Souza <kleber.souza@...onical.com>,
	Marcelo Henrique Cerri <marcelo.cerri@...onical.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched_ext: Provide a sysfs enable_seq counter

On Mon, Sep 23, 2024 at 05:32:15AM -1000 Tejun Heo wrote:
> Hello,
> 
> On Mon, Sep 23, 2024 at 12:45:48PM +0200, Phil Auld wrote:
> ...
> > It's not a per scheduler counter, though. It's global. We want to know
> 
> Yeah, the sequence is global but we can report the sequence at which a given
> scheduler is loaded on each scheduler. That way, e.g., you can tell whether
> a particular scheduler instance is the same one you looked at the last time
> too.
> 
> > that a (any) scx scheduler has been loaded at some time in the past. It's
> > really only interesting when 0 or > 0. The actual non-zero number and which
> > scheduler(s) don't matter that much.
> 
> Not necessarily. e.g. You can also detect scheduler failing or being updated
> for other reasons.

Sure, but the primary purpose is practically boolean. 

> 
> > And it needs to persist when the scheduler is unloaded (I didn't look but
> > I uspect the per scheduler attrs come and go?).
> 
> Yes, the load sequence number should stay persistent across all schedulers,
> but each scheduler should report the sequence number at which *it* was
> loaded. Note that this doesn't really change anything now. If you only care
> whether any SCX scheduler has ever been loaded, you'd always look under
> root.
>

In my testing root is not there is nothing is loaded. 

Cheers,
Phil


> Thanks.
> 
> -- 
> tejun
> 

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