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From: "Li Xinhai" <lixinhai.lxh@gmail.com>
To: mhocko <mhocko@suse.com>
Cc: "linux-mm@kvack.org" <linux-mm@kvack.org>,
	 akpm <akpm@linux-foundation.org>,
	 "Mike Kravetz" <mike.kravetz@oracle.com>
Subject: Re: [PATCH v4] mm/mempolicy,hugetlb: Checking hstate for hugetlbfs page in vma_migratable
Date: Thu, 16 Jan 2020 23:38:20 +0800
Message-ID: <20200116233817972969139@gmail.com> (raw)
In-Reply-To: <20200116151803.GV19428@dhcp22.suse.cz>

On 2020-01-16 at 23:18 Michal Hocko wrote:
>On Thu 16-01-20 21:50:34, Li Xinhai wrote:
>> On 2020-01-16 at 17:56 Michal Hocko wrote:
>> >On Thu 16-01-20 04:11:25, Li Xinhai wrote:
>> >> Checking hstate at early phase when isolating page, instead of during
>> >> unmap and move phase, to avoid useless isolation.
>> >
>> >Could you be more specific what you mean by isolation and why does it
>> >matter? The patch description should really explain _why_ the change is
>> >needed or desirable.
>>
>> The changelog can be improved:
>>
>> vma_migratable() is called to check if pages in vma can be migrated
>> before go ahead to isolate, unmap and move pages. For hugetlb pages,
>> hugepage_migration_supported(struct hstate *h) is one factor which
>> decide if migration is supported. In current code, this function is called
>> from unmap_and_move_huge_page(), after isolating page has
>> completed.
>> This patch checks hstate from vma_migratable() and avoids isolating pages
>> which are not supported.
>
>This still explains what but not why this is relevant. If by isolating
>pages you mean isolate_lru_page then this really a noop for hugetlb
>pages. Or do I still misread your changelog? 

I mean isolate_huge_page will queue pages for moving, and
unmap_and_move_huge_page will call
hugepage_migration_supported then refuse moving.

>--
>Michal Hocko
>SUSE Labs

  reply index

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-16  4:11 Li Xinhai
2020-01-16  9:56 ` Michal Hocko
2020-01-16 13:50   ` Li Xinhai
2020-01-16 15:18     ` Michal Hocko
2020-01-16 15:38       ` Li Xinhai [this message]
2020-01-17  3:16         ` Li Xinhai
2020-01-18  3:11           ` Li Xinhai

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