linux-kernel - Re: [PATCH 4/4] lib/cpumask: don't mention for_each_numa_hop_mask in cpumask_local

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Message-ID: <dbfd06ab-26f3-7b32-6025-2c55e223c576@intel.com>
Date:   Mon, 25 Sep 2023 15:47:57 -0700
From:   Jacob Keller <jacob.e.keller@...el.com>
To:     Yury Norov <yury.norov@...il.com>, <linux-kernel@...r.kernel.org>,
        <netdev@...r.kernel.org>, <linux-rdma@...r.kernel.org>
CC:     Tariq Toukan <ttoukan.linux@...il.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Maher Sanalla <msanalla@...dia.com>,
        Ingo Molnar <mingo@...nel.org>, Mel Gorman <mgorman@...e.de>,
        Saeed Mahameed <saeedm@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...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>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Pawel Chmielewski <pawel.chmielewski@...el.com>,
        Yury Norov <ynorov@...dia.com>
Subject: Re: [PATCH 4/4] lib/cpumask: don't mention for_each_numa_hop_mask in
 cpumask_local_spread()"



On 9/24/2023 7:05 PM, Yury Norov wrote:
> Now that for_each_numa_hop_mask() is reverted, also revert reference to
> it in the comment to cpumask_local_spread().
> 
> This partially reverts commit 2ac4980c57f5 ("lib/cpumask: update comment
> for cpumask_local_spread()")
> 
> Signed-off-by: Yury Norov <yury.norov@...il.com>
> Signed-off-by: Yury Norov <ynorov@...dia.com>
> ---

Interesting to see both sign-offs here. Not sure what that implies here
since both represent you :)

Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>

>  lib/cpumask.c | 21 ---------------------
>  1 file changed, 21 deletions(-)
> 
> diff --git a/lib/cpumask.c b/lib/cpumask.c
> index a7fd02b5ae26..d341fb71a8a9 100644
> --- a/lib/cpumask.c
> +++ b/lib/cpumask.c
> @@ -117,27 +117,6 @@ void __init free_bootmem_cpumask_var(cpumask_var_t mask)
>   *
>   * Returns online CPU according to a numa aware policy; local cpus are returned
>   * first, followed by non-local ones, then it wraps around.
> - *
> - * For those who wants to enumerate all CPUs based on their NUMA distances,
> - * i.e. call this function in a loop, like:
> - *
> - * for (i = 0; i < num_online_cpus(); i++) {
> - *	cpu = cpumask_local_spread(i, node);
> - *	do_something(cpu);
> - * }
> - *
> - * There's a better alternative based on for_each()-like iterators:
> - *
> - *	for_each_numa_hop_mask(mask, node) {
> - *		for_each_cpu_andnot(cpu, mask, prev)
> - *			do_something(cpu);
> - *		prev = mask;
> - *	}
> - *
> - * It's simpler and more verbose than above. Complexity of iterator-based
> - * enumeration is O(sched_domains_numa_levels * nr_cpu_ids), while
> - * cpumask_local_spread() when called for each cpu is
> - * O(sched_domains_numa_levels * nr_cpu_ids * log(nr_cpu_ids)).
>   */
>  unsigned int cpumask_local_spread(unsigned int i, int node)
>  {