linux-kernel - Re: [PATCH 0/2] sched_ext: Add a core event and update scx schedulers

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Message-ID: <aedaba97-08a4-47bd-bb0d-7192dc2a91a5@igalia.com>
Date: Sat, 8 Feb 2025 12:17:26 +0900
From: Changwoo Min <changwoo@...lia.com>
To: Andrea Righi <arighi@...dia.com>, Tejun Heo <tj@...nel.org>
Cc: void@...ifault.com, kernel-dev@...lia.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] sched_ext: Add a core event and update scx schedulers

Hi Tejun and Andrea,

On 25. 2. 8. 06:45, Andrea Righi wrote:
> On Fri, Feb 07, 2025 at 11:38:31AM -1000, Tejun Heo wrote:
>> I'm not sure. BPF schedulers should be able to avoid getting the default
>> slice. Hopefully, with the added visibility, this should be easier now. I'm
>> not sure how much overriding the default value in ops helps in terms of
>> control. It's a very half-way measure. Instead, how about we add tracepoint
>> to scx_add_event() so that folks who want to get backtrace of specific
>> events can get them easily so that it's easier to debug where these counts
>> are coming from? Let's just make it easier to avoid these events.
> 
> Yeah, that's a valid point, the implicit SCX_SLICE_DFL should be seen as a
> countermeasure for unhandled situations. Instead of fixing the
> countermeasure itself we should try to prevent it, if it proves to be
> problematic. And I like the idea of having a way to backtrace specific
> events.

I agree that adding a tracepoint to scx_add_event() and 
__scx_add_event() is a defenitely useful extension to further 
investigate what's going on. I will take a look.

Regards,
Changwoo Min