linux-kernel - Re: [PATCH v2 3/8] sched/topology: add for_each_numa

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Message-ID: <ZEi3dLvlg/35DUrM@yury-ThinkPad>
Date:   Tue, 25 Apr 2023 22:32:36 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     Valentin Schneider <vschneid@...hat.com>
Cc:     Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        Saeed Mahameed <saeedm@...dia.com>,
        Pawel Chmielewski <pawel.chmielewski@...el.com>,
        Leon Romanovsky <leon@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        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>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Tariq Toukan <tariqt@...dia.com>,
        Gal Pressman <gal@...dia.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Barry Song <baohua@...nel.org>
Subject: Re: [PATCH v2 3/8] sched/topology: add for_each_numa_cpu() macro

On Tue, Apr 25, 2023 at 10:54:48AM +0100, Valentin Schneider wrote:
> On 19/04/23 22:19, Yury Norov wrote:
> > +/**
> > + * for_each_numa_cpu - iterate over cpus in increasing order taking into account
> > + *		       NUMA distances from a given node.
> > + * @cpu: the (optionally unsigned) integer iterator
> > + * @hop: the iterator variable, must be initialized to a desired minimal hop.
> > + * @node: the NUMA node to start the search from.
> > + * @mask: the cpumask pointer
> > + *
> > + * Requires rcu_lock to be held.
> > + */
> > +#define for_each_numa_cpu(cpu, hop, node, mask)					\
> > +	for ((cpu) = 0, (hop) = 0;						\
> > +		(cpu) = sched_numa_find_next_cpu((mask), (cpu), (node), &(hop)),\
> > +		(cpu) < nr_cpu_ids;						\
> > +		(cpu)++)
> > +
> 
> I think we can keep sched_numa_find_next_cpu() as-is, but could we make
> that macro use cpu_possible_mask by default? We can always add a variant
> if/when we need to feed in a different mask.

As mentioned in discussion to the driver's patch, all that numa things
imply only online CPUs, so cpu_possible_mask may mislead to some extent. 

Anyways, can you elaborate what you exactly want? Like this?

 #define for_each_numa_online_cpu(cpu, hop, node)       \
        for_each_numa_cpu(cpu, hop, node, cpu_online_mask)