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Date: Mon, 15 Feb 2016 23:24:22 +0900
Message-ID: <CAAmzW4MVOh+O1q8WUECTyGYtT=exssvA0WDJy0Y9xBFTpKa1Kg@mail.gmail.com>
Subject: Re: [PATCH v2 3/3] mm/compaction: speed up pageblock_pfn_to_page()
 when zone is contiguous
From: Joonsoo Kim <js1304@gmail.com>
To: Xishi Qiu <qiuxishi@huawei.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>, zhong jiang <zhongjiang@huawei.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Vlastimil Babka <vbabka@suse.cz>, Aaron Lu <aaron.lu@intel.com>,
        Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@redhat.com>,
        David Rientjes <rientjes@google.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux Memory Management List <linux-mm@kvack.org>
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2016-02-15 19:06 GMT+09:00 Xishi Qiu <qiuxishi@huawei.com>:
> 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?

Yes.

Thanks.