linux-kernel - Re: [PATCH 2/5] genirq: Allow the affinity of a percpu interrupt to be set/retrieved

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Message-ID: <573DBBFA.8020903@arm.com>
Date:	Thu, 19 May 2016 14:13:30 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	Jason Cooper <jason@...edaemon.net>,
	Will Deacon <will.deacon@....com>,
	Mark Rutland <mark.rutland@....com>,
	Rob Herring <robh+dt@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 2/5] genirq: Allow the affinity of a percpu interrupt to
 be set/retrieved

Hi Geert,

On 19/05/16 12:08, Geert Uytterhoeven wrote:
> Hi Marc,
> 
> On Mon, Apr 11, 2016 at 10:57 AM, Marc Zyngier <marc.zyngier@....com> wrote:
>> In order to prepare the genirq layer for the concept of partitionned
>> percpu interrupts, let's allow an affinity to be associated with
>> such an interrupt. We introduce:
>>
>> - irq_set_percpu_devid_partition: flag an interrupt as a percpu-devid
>>   interrupt, and associate it with an affinity
>> - irq_get_percpu_devid_partition: allow the affinity of that interrupt
>>   to be retrieved.
>>
>> This will allow a driver to discover which CPUs the per-cpu interrupt
>> can actually fire on.
>>
>> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> 
>> --- a/include/linux/irqdesc.h
>> +++ b/include/linux/irqdesc.h
>> @@ -66,6 +66,7 @@ struct irq_desc {
>>         int                     threads_handled_last;
>>         raw_spinlock_t          lock;
>>         struct cpumask          *percpu_enabled;
>> +       const struct cpumask    *percpu_affinity;
> 
> Adding this field showed up on my bloat-o-meter radar...

By how much?

> Does it make sense to move it (and percpu_enabled) inside the "#ifdef
> CONFIG_SMP" below, and rework the code to not need it on UP?
> 
>>  #ifdef CONFIG_SMP
>>         const struct cpumask    *affinity_hint;
>>         struct irq_affinity_notify *affinity_notify;

I wonder if we couldn't actually unify affinity_hint and
percpu_affinity. I'll have a look.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...