linux-kernel - Re: [patch 1/4] Make the per cpu reserve configurable

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Date:	Sat, 20 Sep 2008 12:55:46 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, jeremy@...p.org, ebiederm@...ssion.com,
	travis@....com, herbert@...dor.apana.org.au, xemul@...nvz.org,
	penberg@...helsinki.fi
Subject: Re: [patch 1/4] Make the per cpu reserve configurable

On Fri, 19 Sep 2008 07:59:00 -0700
Christoph Lameter <cl@...ux-foundation.org> wrote:
> +unsigned int percpu_reserve = PERCPU_MODULE_RESERVE;
> +

Is this PERCPU_MODULE_RESERVE default size is fixex to 8192 bytes
both on 32bit-arch and 64bit-arch ?
How about enlarging this to twice on 64bit arch now ?

sorry for noise.

Thanks,
-Kame



> +static int __init init_percpu_reserve(char *str)
> +{
> +	get_option(&str, &percpu_reserve);
> +	return 0;
> +}
> +
> +early_param("percpu=", init_percpu_reserve);
> +
>  /*
>   * Unknown boot options get handed to init, unless they look like
>   * failed parameters
> @@ -397,6 +407,9 @@ static void __init setup_per_cpu_areas(v
>  
>  	/* Copy section for each CPU (we discard the original) */
>  	size = ALIGN(PERCPU_ENOUGH_ROOM, PAGE_SIZE);
> +	printk(KERN_INFO "percpu area: %d bytes total, %d available.\n",
> +			size, size - (__per_cpu_end - __per_cpu_start));
> +
>  	ptr = alloc_bootmem_pages(size * nr_possible_cpus);
>  
>  	for_each_possible_cpu(i) {
> Index: linux-2.6/Documentation/kernel-parameters.txt
> ===================================================================
> --- linux-2.6.orig/Documentation/kernel-parameters.txt	2008-09-16 18:14:59.000000000 -0700
> +++ linux-2.6/Documentation/kernel-parameters.txt	2008-09-16 18:20:08.000000000 -0700
> @@ -1643,6 +1643,13 @@ and is between 256 and 4096 characters. 
>  			Format: { 0 | 1 }
>  			See arch/parisc/kernel/pdc_chassis.c
>  
> +	percpu=		Configure the number of percpu bytes that can be
> +			dynamically allocated. This is used for per cpu
> +			variables of modules and other dynamic per cpu data
> +			structures. Creation of per cpu structures after boot
> +			may fail if this is set too low.
> +			Default is 8000 bytes.
> +
>  	pf.		[PARIDE]
>  			See Documentation/paride.txt.
>  
> 
> -- 
> 
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