linux-kernel - Re: [PATCHSET v6] sched: Implement BPF extensible scheduler class

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Message-ID: <20240503085232.GC30852@noisy.programming.kicks-ass.net>
Date: Fri, 3 May 2024 10:52:32 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Tejun Heo <tj@...nel.org>
Cc: torvalds@...ux-foundation.org, mingo@...hat.com, juri.lelli@...hat.com,
	vincent.guittot@...aro.org, dietmar.eggemann@....com,
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Subject: Re: [PATCHSET v6] sched: Implement BPF extensible scheduler class

On Thu, May 02, 2024 at 09:20:15AM -1000, Tejun Heo wrote:
> Hello, Peter.
> 
> On Thu, May 02, 2024 at 10:48:00AM +0200, Peter Zijlstra wrote:
> > Can you please put your efforts and the touted Google collaboration in
> > fixing the existing cgroup mess?
> 
> I suppose you're referring to Rik's flattened hierarchy patchset.
> 
>   https://lore.kernel.org/all/20190822021740.15554-1-riel@surriel.com
> 
> Rik spent a lot of time and energy on it and IIRC one of the reasons why it
> didn't get pushed further was the lack of any enthusiasm or support from the
> upstream community.
> 
> We can resurrect the discussion on that patchset but how is that connected
> to sched_ext? 

I'm absolutely not taking any of this until at the very least the cgroup
situation that's been created is solved. And even then, I fundamentally
believe the approach to be detrimental to the scheduler eco-system.
Witness the metric ton of toy schedulers written for it, that's all
effort not put into improving the existing code.

You guys Google/Facebook got us the cgroup thing, Google did a lot of
the work for cpu-cgroup, and now you Facebook say you can't live with it
because it's too expensive. Yes Rik did put a lot of effort into it, but
Google shot it down. What am I to do?

You Google/Facebook are touting collaboration, collaborate on fixing it.
Instead of re-posting this over and over. After all, your main
motivation for starting this was the cpu-cgroup overhead.

>From where I'm sitting, you created a problem (cpu-cgroup) and now
you're creating an even bigger problem as a work-around. Very much not
appreciated.