linux-kernel - Re: [PATCH 09/30] sched_ext: Implement BPF extensible scheduler class

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Message-ID: <20240807210431.GB80631@pauld.westford.csb>
Date: Wed, 7 Aug 2024 17:04:31 -0400
From: Phil Auld <pauld@...hat.com>
To: Tejun Heo <tj@...nel.org>
Cc: torvalds@...ux-foundation.org, mingo@...hat.com, peterz@...radead.org,
	juri.lelli@...hat.com, vincent.guittot@...aro.org,
	dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
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	daniel@...earbox.net, andrii@...nel.org, martin.lau@...nel.org,
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	joel@...lfernandes.org, linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org, kernel-team@...a.com
Subject: Re: [PATCH 09/30] sched_ext: Implement BPF extensible scheduler class

Hi Tejun,

On Wed, Aug 07, 2024 at 09:26:28AM -1000 Tejun Heo wrote:
> Hello, Phil.
> 
> On Wed, Aug 07, 2024 at 03:11:08PM -0400, Phil Auld wrote:
> > On Tue, Jun 18, 2024 at 11:17:24AM -1000 Tejun Heo wrote:
> > > Implement a new scheduler class sched_ext (SCX), which allows scheduling
> > > policies to be implemented as BPF programs to achieve the following:
> > > 
> > 
> > I looks like this is slated for v6.12 now?  That would be good. My initial
> > experimentation with scx has been positive.
> 
> Yeap and great to hear.
> 
> > I just picked one email, not completely randomly.
> > 
> > > - Both enable and disable paths are a bit complicated. The enable path
> > >   switches all tasks without blocking to avoid issues which can arise from
> > >   partially switched states (e.g. the switching task itself being starved).
> > >   The disable path can't trust the BPF scheduler at all, so it also has to
> > >   guarantee forward progress without blocking. See scx_ops_enable() and
> > >   scx_ops_disable_workfn().
> > 
> > I think, from a supportability point of view, there needs to be a pr_info, at least,
> > in each of these places, enable and disable, with the name of the scx scheduler. It
> > looks like there is at least a pr_error for when one gets ejected due to misbehavior.
> > But there needs to be a record of when such is loaded and unloaded.
> 
> Sure, that's not difficult. Will do so soon.

Thanks! That would be helpful.  I was going to offer a patch but wanted to ask first
in case there was history.

But if you are willing to do it that's even better :) 


Cheers,
Phil


> 
> Thanks.
> 
> -- 
> tejun
> 

--