linux-kernel - Re: [PATCH 1/2] kernel/smp: Make the SMP boot message common on all arches

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Message-ID: <20161016070406.GA4211@gmail.com>
Date:   Sun, 16 Oct 2016 09:04:06 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     akpm@...l.org, tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        x86@...nel.org, peterz@...radead.org, jgross@...e.com,
        mgorman@...hsingularity.net, richard@....at, len.brown@...el.com,
        bp@...e.de, boris.ostrovsky@...cle.com, tim.c.chen@...ux.intel.com,
        ak@...ux.intel.com, jolsa@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] kernel/smp: Make the SMP boot message common on all
 arches


* Michael Ellerman <mpe@...erman.id.au> wrote:

> Currently after bringing up secondary CPUs all arches print "Brought up
> %d CPUs". On x86 they also print the number of nodes that were brought
> online.
> 
> It would be nice to also print the number of nodes on other arches.
> Although we could override smp_announce() on the other ~10 NUMA aware
> arches, it seems simpler to just always print the number of nodes. On
> non-NUMA arches there is just always 1 node.
> 
> Having done that, smp_announce() is no longer weak, and seems small
> enough to just pull directly into smp_init().
> 
> Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
> ---
>  arch/x86/kernel/smpboot.c |  8 --------
>  kernel/smp.c              | 11 +++++------
>  2 files changed, 5 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index 42a93621f5b0..7eb8dfa56d34 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -821,14 +821,6 @@ wakeup_secondary_cpu_via_init(int phys_apicid, unsigned long start_eip)
>  	return (send_status | accept_status);
>  }
>  
> -void smp_announce(void)
> -{
> -	int num_nodes = num_online_nodes();
> -
> -	printk(KERN_INFO "x86: Booted up %d node%s, %d CPUs\n",
> -	       num_nodes, (num_nodes > 1 ? "s" : ""), num_online_cpus());
> -}
> -
>  /* reduce the number of lines printed when booting a large cpu count system */
>  static void announce_cpu(int cpu, int apicid)
>  {
> diff --git a/kernel/smp.c b/kernel/smp.c
> index bba3b201668d..6f5696d260c8 100644
> --- a/kernel/smp.c
> +++ b/kernel/smp.c
> @@ -543,15 +543,11 @@ void __init setup_nr_cpu_ids(void)
>  	nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1;
>  }
>  
> -void __weak smp_announce(void)
> -{
> -	printk(KERN_INFO "Brought up %d CPUs\n", num_online_cpus());
> -}
> -
>  /* Called by boot processor to activate the rest. */
>  void __init smp_init(void)
>  {
>  	unsigned int cpu;
> +	int num_nodes;
>  
>  	idle_threads_init();
>  	cpuhp_threads_init();
> @@ -564,8 +560,11 @@ void __init smp_init(void)
>  			cpu_up(cpu);
>  	}
>  
> +	num_nodes = num_online_nodes();
> +	pr_info("smp: Brought up %d node%s, %d CPUs\n",
> +		num_nodes, (num_nodes > 1 ? "s" : ""), num_online_cpus());

No objections - but pedantry requires me to mention that while we are evolving 
this code and changing the strings I think we should make the CPU announcement 
CPU%s smart as well: an SMP kernel on a single CPU bootup will result in 
num_online_cpus() == 1, right?

Thanks,

	Ingo