linux-kernel - Re: [PATCH] Use NUMA node cpu mask in irq affinity

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Message-ID: <alpine.LFD.2.02.1202091132590.2794@ionos>
Date:	Thu, 9 Feb 2012 11:36:39 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Prarit Bhargava <prarit@...hat.com>
cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Use NUMA node cpu mask in irq affinity

On Wed, 8 Feb 2012, Prarit Bhargava wrote:

Could you please CC the relevant maintainers ?

> The irq affinity files (/proc/irq/.../smp_affinity) contain a mask that is used
> to "pin" an irq to a set of cpus.  On boot this set is currently all cpus.
> This can be incorrect as ACPI SRAT may tell us that a specific device or
> bus is attached to a particular node and it's cpus.
> 
> When setting up the irq affinity we should take into account the NUMA node
> cpu mask by and'ing it into the irq's affinity mask.
> 
> Signed-off-by: Prarit Bhargava <prarit@...hat.com>
> Acked-by: Neil Horman <nhorman@...driver.com>
> ---
>  kernel/irq/manage.c |    2 ++
>  1 files changed, 2 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
> index a9a9dbe..2fb3469 100644
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -301,6 +301,8 @@ setup_affinity(unsigned int irq, struct irq_desc *desc, struct cpumask *mask)
>  	}
>  
>  	cpumask_and(mask, cpu_online_mask, set);
> +	if (desc->irq_data.node != -1)
> +		cpumask_and(mask, mask, cpumask_of_node(desc->irq_data.node));

What prevents mask from becoming empty if mask does not intersect with
the node mask?

Thanks,

	tglx
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