linux-kernel - Re: [PATCH 5/6] sched_ext: idle: Per-node idle cpumasks

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Message-ID: <Z6r_NZui9GibrQHY@gpd3>
Date: Tue, 11 Feb 2025 08:41:41 +0100
From: Andrea Righi <arighi@...dia.com>
To: Yury Norov <yury.norov@...il.com>
Cc: Tejun Heo <tj@...nel.org>, David Vernet <void@...ifault.com>,
	Changwoo Min <changwoo@...lia.com>, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>, Ian May <ianm@...dia.com>,
	bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/6] sched_ext: idle: Per-node idle cpumasks

On Tue, Feb 11, 2025 at 08:32:51AM +0100, Andrea Righi wrote:
> On Mon, Feb 10, 2025 at 11:57:42AM -0500, Yury Norov wrote:
> ...
> > > > +/*
> > > > + * Find the best idle CPU in the system, relative to @node.
> > > > + */
> > > > +s32 scx_pick_idle_cpu(const struct cpumask *cpus_allowed, int node, u64 flags)
> > > > +{
> > > > +	nodemask_t unvisited = NODE_MASK_ALL;
> > 
> > This should be a NODEMASK_ALLOC(). We don't want to eat up too much of the
> > stack, right?
> 
> Ok, and if I want to initialize unvisited to all online nodes, is there a
> better than doing:
> 
>   nodemask_clear(*unvisited);
>   nodemask_or(*unvisited, *unvisited, node_states[N_ONLINE]);
> 
> We don't have nodemask_copy() right?

Sorry, and with that I mean nodes_clear() / nodes_or() / nodes_copy().

-Andrea