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From: Peter Zijlstra <peterz@infradead.org>
To: Lauro Ramos Venancio <lvenanci@redhat.com>
Cc: linux-kernel@vger.kernel.org, lwang@redhat.com, riel@redhat.com,
	Mike Galbraith <efault@gmx.de>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@kernel.org>
Subject: Re: [RFC 2/3] sched/topology: fix sched groups on NUMA machines with mesh topology
Date: Fri, 14 Apr 2017 18:58:57 +0200
Message-ID: <20170414165857.7n75lxk4usfsbjaq@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20170414113813.vktcpsrsuu2st2fm@hirez.programming.kicks-ass.net>

On Fri, Apr 14, 2017 at 01:38:13PM +0200, Peter Zijlstra wrote:
> On Thu, Apr 13, 2017 at 10:56:08AM -0300, Lauro Ramos Venancio wrote:
> > This patch constructs the sched groups from each CPU perspective. So, on
> > a 4 nodes machine with ring topology, while nodes 0 and 2 keep the same
> > groups as before [(3, 0, 1)(1, 2, 3)], nodes 1 and 3 have new groups
> > [(0, 1, 2)(2, 3, 0)]. This allows moving tasks between any node 2-hops
> > apart.
> 
> Ah,.. so after drawing pictures I see what went wrong; duh :-(
> 
> An equivalent patch would be (if for_each_cpu_wrap() were exposed):
> 
> @@ -521,11 +588,11 @@ build_overlap_sched_groups(struct sched_domain *sd, int cpu)
>  	struct cpumask *covered = sched_domains_tmpmask;
>  	struct sd_data *sdd = sd->private;
>  	struct sched_domain *sibling;
> -	int i;
> +	int i, wrap;
>  
>  	cpumask_clear(covered);
>  
> -	for_each_cpu(i, span) {
> +	for_each_cpu_wrap(i, span, cpu, wrap) {
>  		struct cpumask *sg_span;
>  
>  		if (cpumask_test_cpu(i, covered))
> 
> 
> We need to start iterating at @cpu, not start at 0 every time.
> 
> 

OK, please have a look here:

https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/log/?h=sched/core

  parent reply index

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-13 13:56 [RFC 0/3] " Lauro Ramos Venancio
2017-04-13 13:56 ` [RFC 1/3] sched/topology: Refactor function build_overlap_sched_groups() Lauro Ramos Venancio
2017-04-13 14:50   ` Rik van Riel
2017-05-15  9:02   ` [tip:sched/core] " tip-bot for Lauro Ramos Venancio
2017-04-13 13:56 ` [RFC 2/3] sched/topology: fix sched groups on NUMA machines with mesh topology Lauro Ramos Venancio
2017-04-13 15:16   ` Rik van Riel
2017-04-13 15:48   ` Peter Zijlstra
2017-04-13 20:21     ` Lauro Venancio
2017-04-13 21:06       ` Lauro Venancio
2017-04-13 23:38         ` Rik van Riel
2017-04-14 10:48           ` Peter Zijlstra
2017-04-14 11:38   ` Peter Zijlstra
2017-04-14 12:20     ` Peter Zijlstra
2017-05-15  9:03       ` [tip:sched/core] sched/fair, cpumask: Export for_each_cpu_wrap() tip-bot for Peter Zijlstra
2017-05-17 10:53         ` hackbench vs select_idle_sibling; was: " Peter Zijlstra
2017-05-17 12:46           ` Matt Fleming
2017-05-17 14:49           ` Chris Mason
2017-05-19 15:00           ` Matt Fleming
2017-06-05 13:00             ` Matt Fleming
2017-06-06  9:21               ` Peter Zijlstra
2017-06-09 17:52                 ` Chris Mason
2017-06-08  9:22           ` [tip:sched/core] sched/core: Implement new approach to scale select_idle_cpu() tip-bot for Peter Zijlstra
2017-04-14 16:58     ` Peter Zijlstra [this message]
2017-04-17 14:40       ` [RFC 2/3] sched/topology: fix sched groups on NUMA machines with mesh topology Lauro Venancio
2017-04-13 13:56 ` [RFC 3/3] sched/topology: Different sched groups must not have the same balance cpu Lauro Ramos Venancio
2017-04-13 15:27   ` Rik van Riel
2017-04-14 16:49   ` Peter Zijlstra
2017-04-17 15:34     ` Lauro Venancio
2017-04-18 12:32       ` Peter Zijlstra

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