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

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Date:	Thu, 09 Feb 2012 08:52:45 -0500
From:	Prarit Bhargava <prarit@...hat.com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] Use NUMA node cpu mask in irq affinity



On 02/08/2012 06:51 PM, Yinghai Lu wrote:
> On Wed, Feb 8, 2012 at 12:48 PM, Prarit Bhargava <prarit@...hat.com> wrote:
>> 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));
>>        ret = chip->irq_set_affinity(&desc->irq_data, mask, false);
>>        switch (ret) {
>>        case IRQ_SET_MASK_OK:
>> --
> 
> How about all cpus on that node get offlined?

Good point.  I guess that also goes to tglx's comments wondering what happens if the mask ends up being zero.

I'll think about that and send out a new patch shortly.

P.
> 
> Yinghai
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