linux-kernel - Re: [patch] mm: speedup in __early_pfn_to

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Date:	Mon, 25 Mar 2013 10:11:27 +0800
From:	Lin Feng <linfeng@...fujitsu.com>
To:	Yinghai Lu <yinghai@...nel.org>, Russ Anderson <rja@....com>
CC:	Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	David Rientjes <rientjes@...gle.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
	hpa@...or.com
Subject: Re: [patch] mm: speedup in __early_pfn_to_nid



On 03/24/2013 04:37 AM, Yinghai Lu wrote:
> +#ifdef CONFIG_HAVE_MEMBLOCK_NODE_MAP
> +int __init_memblock memblock_search_pfn_nid(unsigned long pfn,
> +			 unsigned long *start_pfn, unsigned long *end_pfn)
> +{
> +	struct memblock_type *type = &memblock.memory;
> +	int mid = memblock_search(type, (phys_addr_t)pfn << PAGE_SHIFT);

I'm really eager to see how much time can we save using binary search compared to
linear search in this case :)

(quote)
> A 4 TB (single rack) UV1 system takes 512 seconds to get through
> the zone code.  This performance optimization reduces the time
> by 189 seconds, a 36% improvement.
>
> A 2 TB (single rack) UV2 system goes from 212.7 seconds to 99.8 seconds,
> a 112.9 second (53%) reduction.
(quote)

thanks,
linfeng
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