linux-kernel - Re: [PATCH v2 3/3] mm/compaction: speed up pageblock_pfn_to

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Date:	Mon, 15 Feb 2016 18:06:08 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
CC:	zhong jiang <zhongjiang@...wei.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Aaron Lu <aaron.lu@...el.com>, Mel Gorman <mgorman@...e.de>,
	Rik van Riel <riel@...hat.com>,
	David Rientjes <rientjes@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [PATCH v2 3/3] mm/compaction: speed up pageblock_pfn_to_page()
 when zone is contiguous

On 2016/2/15 10:42, Joonsoo Kim wrote:

>>
>> I have a question about the zone continuity. because hole exists at
>> arbitrary position in a page block. Therefore, only pageblock_pf_to_page()
>> is insufficiency, whether pageblock aligned pfn or not , the pfn_valid_within()
>> is necessary.
>>
>> eh: 120M-122M is a range of page block, but the 120.5M-121.5M is holes, only by
>> pageblock_pfn_to_page() to conclude in the result is inaccurate
> 
> contiguous may be misleading word. It doesn't represent there are no
> hole. It only represents that all pageblocks within zone span belong to
> corresponding zone and validity of all pageblock aligned pfn is
> checked. So, if it is set, we can safely call pfn_to_page() for pageblock
> aligned pfn in that zone without checking pfn_valid().
> 
> Thanks.
> 

Hi Joonsoo,

So "contiguous" here only means that struct page is exist, and don't care whether
the memory is exist, right?

Thanks,
Xishi Qiu

> 
> .
>