linux-kernel - Re: [PATCH v2] sched/isolation: Prefer housekeeping cpu in local node

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Date:   Fri, 21 Jun 2019 08:58:42 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Wanpeng Li <kernellwp@...il.com>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Frederic Weisbecker <frederic@...nel.org>
Subject: Re: [PATCH v2] sched/isolation: Prefer housekeeping cpu in local node

On Fri, Jun 21, 2019 at 09:35:11AM +0800, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@...cent.com>
> 
> In real product setup, there will be houseeking cpus in each nodes, it 
> is prefer to do housekeeping from local node, fallback to global online 
> cpumask if failed to find houseeking cpu from local node.
> 
> Cc: Ingo Molnar <mingo@...hat.com> 
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Frederic Weisbecker <frederic@...nel.org>
> Signed-off-by: Wanpeng Li <wanpengli@...cent.com>

Looks good; did it actually work? :-)

> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index 63184cf..3d3fb04 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -1726,6 +1726,20 @@ void sched_domains_numa_masks_clear(unsigned int cpu)
>  
>  #endif /* CONFIG_NUMA */


Please double check this function; I wrote it in a hurry :-) Also maybe
add a wee comment on top like:

/*
 * sched_numa_file_closest() - given the NUMA topology, find the cpu
 *                             closest to @cpu from @cpumask.
 * cpumask: cpumask to find a cpu from
 * cpu: cpu to be close to
 *
 * returns: cpu, or >= nr_cpu_ids when nothing found (or !NUMA).
 */

> +int sched_numa_find_closest(const struct cpumask *cpus, int cpu)
> +{
> +#ifdef CONFIG_NUMA
> +	int i, j = cpu_to_node(cpu);
> +
> +	for (i = 0; i < sched_domains_numa_levels; i++) {
> +		cpu = cpumask_any_and(cpus, sched_domains_numa_masks[i][j]);
> +		if (cpu < nr_cpu_ids)
> +			return cpu;
> +	}
> +#endif
> +	return nr_cpu_ids;
> +}