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Subject: Re: [PATCH] Enable hashdist by default on PowerPC
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Anton Blanchard <anton@samba.org>
In-Reply-To: <20090218051112.GA32195@kryten>
References: <20090218051112.GA32195@kryten>
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Date: Wed, 18 Feb 2009 16:41:07 +1100
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> For many HPC applications we are limited by the free available memory on
> the smallest node, so even though the same amount of memory is used the
> better balancing helps.
> 
> Signed-off-by: Anton Blanchard <anton@samba.org>
> ---

You have numbers ? :-) I'm asking mostly because I've been wondering
whether it offsets the 16M pages vs. 4K or 64K pages in term of TLB/ERAT
impact.

Cheers,
Ben.

> diff --git a/include/linux/bootmem.h b/include/linux/bootmem.h
> index 95837bf..c0c63ee 100644
> --- a/include/linux/bootmem.h
> +++ b/include/linux/bootmem.h
> @@ -145,9 +145,10 @@ extern void *alloc_large_system_hash(const char *tablename,
>  #define HASH_EARLY	0x00000001	/* Allocating during early boot? */
>  
>  /* Only NUMA needs hash distribution.
> - * IA64 and x86_64 have sufficient vmalloc space.
> + * IA64, x86_64 and PowerPC have sufficient vmalloc space.
>   */
> -#if defined(CONFIG_NUMA) && (defined(CONFIG_IA64) || defined(CONFIG_X86_64))
> +#if defined(CONFIG_NUMA) && (defined(CONFIG_IA64) || defined(CONFIG_X86_64) || \
> +	defined(CONFIG_PPC64))
>  #define HASHDIST_DEFAULT 1
>  #else
>  #define HASHDIST_DEFAULT 0
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