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From: Tejun Heo <tj@kernel.org>
To: Andrea Righi <arighi@nvidia.com>
Cc: David Vernet <void@manifault.com>,
	Changwoo Min <changwoo@igalia.com>,
	bpf@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCHSET sched_ext/for-6.15] sched_ext: Enhance built-in idle selection with preferred CPUs
Date: Thu, 6 Mar 2025 08:34:15 -1000	[thread overview]
Message-ID: <Z8nqpyEQmmff9E8X@slm.duckdns.org> (raw)
In-Reply-To: <20250306182544.128649-1-arighi@nvidia.com>

Hello,

On Thu, Mar 06, 2025 at 07:18:03PM +0100, Andrea Righi wrote:
> To implement this, introduce a new helper kfunc scx_bpf_select_cpu_pref()
> that allows to specify a cpumask of preferred CPUs:
> 
> s32 scx_bpf_select_cpu_pref(struct task_struct *p,
> 			    const struct cpumask *preferred_cpus,
> 			    s32 prev_cpu, u64 wake_flags, u64 flags);
> 
> Moreover, introduce the new idle flag %SCX_PICK_IDLE_IN_PREF that can be
> used to enforce selection strictly within the preferred domain.

Would something like scx_bpf_select_cpu_and() work which is only allowed
pick in the intersection (ie. always SCX_PICK_IDLE_IN_PREF). I'm not sure
how much more beneficial a built-in two-level mechanism is especially given
that it wouldn't be too uncommon to need multi-level pick - e.g. within l3
then within numa node and so on.

Thanks.

-- 
tejun

  parent reply	other threads:[~2025-03-06 18:34 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-03-06 18:18 [PATCHSET sched_ext/for-6.15] sched_ext: Enhance built-in idle selection with preferred CPUs Andrea Righi
2025-03-06 18:18 ` [PATCH 1/4] sched_ext: idle: Honor idle flags in the built-in idle selection policy Andrea Righi
2025-03-06 18:18 ` [PATCH 2/4] sched_ext: idle: Introduce the concept of preferred CPUs Andrea Righi
2025-03-06 18:18 ` [PATCH 3/4] sched_ext: idle: Introduce scx_bpf_select_cpu_pref() Andrea Righi
2025-03-07  3:15   ` Changwoo Min
2025-03-07  6:35     ` Andrea Righi
2025-03-06 18:18 ` [PATCH 4/4] selftests/sched_ext: Add test for scx_bpf_select_cpu_pref() Andrea Righi
2025-03-06 18:34 ` Tejun Heo [this message]
2025-03-06 18:54   ` [PATCHSET sched_ext/for-6.15] sched_ext: Enhance built-in idle selection with preferred CPUs Andrea Righi
2025-03-06 18:58     ` Tejun Heo
2025-03-06 19:02       ` Andrea Righi
2025-03-07  3:14 ` Changwoo Min

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