linux-kernel - Re: [PATCH 5/8] x86/apic: Try to spread IRQ vectors to different priority levels

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Date:	Thu, 07 Jun 2012 15:26:03 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	Alexander Gordeev <agordeev@...hat.com>
Cc:	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	x86@...nel.org, Yinghai Lu <yinghai@...nel.org>
Subject: Re: [PATCH 5/8] x86/apic: Try to spread IRQ vectors to different
 priority levels

On Thu, 2012-06-07 at 15:15 +0200, Alexander Gordeev wrote:
> When assigning a new vector it is primarially done by adding 8 to the
> previously given out vector number. Hence, two consequently allocated
> vector numbers would likely fall into the same priority level. Try to
> spread vector numbers to different priority levels better by changing
> the step from 8 to 16.
> 

Acked-by: Suresh Siddha <suresh.b.siddha@...el.com>

> Signed-off-by: Alexander Gordeev <agordeev@...hat.com>
> ---
>  arch/x86/kernel/apic/io_apic.c |    7 +++----
>  1 files changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
> index 74c5697..05af3d3 100644
> --- a/arch/x86/kernel/apic/io_apic.c
> +++ b/arch/x86/kernel/apic/io_apic.c
> @@ -1112,7 +1112,7 @@ __assign_irq_vector(int irq, struct irq_cfg *cfg, const struct cpumask *mask)
>  	 * 0x80, because int 0x80 is hm, kind of importantish. ;)
>  	 */
>  	static int current_vector = FIRST_EXTERNAL_VECTOR + VECTOR_OFFSET_START;
> -	static int current_offset = VECTOR_OFFSET_START % 8;
> +	static int current_offset = VECTOR_OFFSET_START % 16;
>  	unsigned int old_vector;
>  	int cpu, err;
>  	cpumask_var_t tmp_mask;
> @@ -1148,10 +1148,9 @@ __assign_irq_vector(int irq, struct irq_cfg *cfg, const struct cpumask *mask)
>  		vector = current_vector;
>  		offset = current_offset;
>  next:
> -		vector += 8;
> +		vector += 16;
>  		if (vector >= first_system_vector) {
> -			/* If out of vectors on large boxen, must share them. */
> -			offset = (offset + 1) % 8;
> +			offset = (offset + 1) % 16;
>  			vector = FIRST_EXTERNAL_VECTOR + offset;
>  		}
>  		if (unlikely(current_vector == vector))
> -- 
> 1.7.7.6
> 


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