linux-kernel - Re: [PATCH] x86: use nr_cpus in max_nr

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Message-ID: <496B8C9A.5000905@sgi.com>
Date:	Mon, 12 Jan 2009 10:31:54 -0800
From:	Mike Travis <travis@....com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	Ingo Molnar <mingo@...e.hu>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: use nr_cpus in max_nr_irqs()

Yinghai Lu wrote:
> Impact: get more small nr_irqs
> 
> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> 
> ---
>  arch/x86/include/asm/apicdef.h     |    7 +------
>  arch/x86/include/asm/irq_vectors.h |    4 ++--
>  2 files changed, 3 insertions(+), 8 deletions(-)
> 
> Index: linux-2.6/arch/x86/include/asm/irq_vectors.h
> ===================================================================
> --- linux-2.6.orig/arch/x86/include/asm/irq_vectors.h
> +++ linux-2.6/arch/x86/include/asm/irq_vectors.h
> @@ -122,8 +122,8 @@
>  
>  /* defined as a macro so nr_irqs = max_nr_irqs(nr_cpu_ids) can be used */
>  # define max_nr_irqs(nr_cpus)				\
> -	((8 * nr_cpus) > (32 * MAX_IO_APICS) ?		\
> -		(NR_VECTORS + (8 * NR_CPUS)) :		\
> +	((8 * (nr_cpus)) > (32 * MAX_IO_APICS) ?		\
> +		(NR_VECTORS + (8 * (nr_cpus)) :		\
>  		(NR_VECTORS + (32 * MAX_IO_APICS)))	\
>  
>  # define NR_IRQS max_nr_irqs(NR_CPUS)

Did I really miss that?  I guess the reduction from 33024 to 4352
was sufficient for me... ;-)

Hey, a question... Can I determine what the maximum apic id would be?
Right now it's fixed at 32k but that seems high even for 4096 cpus?
(MAX_APICS].

Thanks!
Mike

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