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From: Mike Kravetz <mike.kravetz@oracle.com>
To: Li Xinhai <lixinhai.lxh@gmail.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>
Cc: akpm <akpm@linux-foundation.org>, mhocko <mhocko@suse.com>,
	"yang.shi" <yang.shi@linux.alibaba.com>,
	n-horiguchi <n-horiguchi@ah.jp.nec.com>
Subject: Re: [PATCH 2/2] mm/mempolicy: Skip walking HUGETLB vma if MPOL_MF_STRICT is specified alone
Date: Tue, 14 Jan 2020 17:07:50 -0800	[thread overview]
Message-ID: <a2f0b0be-e9f1-bef6-1fab-c9d1a556d57a@oracle.com> (raw)
In-Reply-To: <2020011422092314671410@gmail.com>

On 1/14/20 6:09 AM, Li Xinhai wrote:
> Add cc to
> Yang Shi <yang.shi@linux.alibaba.com>
> Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> , who has been worked on this part
> 
> On 2020-01-14 at 17:16 Li Xinhai wrote:
>> Checking MPOL_MF_STRICT is ignored for HUGETLB vma according to mbind man
>> page:
>>
>> Notes
>> MPOL_MF_STRICT is ignored on huge page mappings.
>>
>> If MPOL_MF_STRICT is specified alone without any MOVE flag, we should
>> indicate, from test_walk, that walking this vma should be skipped even if
>> there are misplaced pages.
>>
>> Signed-off-by: Li Xinhai <lixinhai.lxh@gmail.com>
>> Cc: Michal Hocko <mhocko@suse.com>
>> Cc: Mike Kravetz <mike.kravetz@oracle.com>

I do not necessarily disagree with the change.  However, this has made me
question a couple things:
1) Why does the man page say MPOL_MF_STRICT is ignored on huge page mappings?
   - Is that leftover from the the days when huge page migration was not
     supported?
   - Is it just because huge page migration is more likely to fail than
     base page migration.
2) Does the mbind code function properly when unable to migrate a huge page
   MPOL_MF_STRICT is set?  A quick look at the code looks like it returns
   EIO.

I will look into these questions.  However, if someone already knows the
answer that would be appreciated.
-- 
Mike Kravetz


  parent reply	other threads:[~2020-01-15  1:08 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-14  9:16 [PATCH 1/2] mm/mempolicy: Checking hstate for hugetlbfs page in vma_migratable Li Xinhai
2020-01-14  9:16 ` [PATCH 2/2] mm/mempolicy: Skip walking HUGETLB vma if MPOL_MF_STRICT is specified alone Li Xinhai
2020-01-14 14:09   ` Li Xinhai
2020-01-14 18:27     ` Yang Shi
2020-01-15  1:07     ` Mike Kravetz [this message]
2020-01-15  1:24       ` Yang Shi
2020-01-15  4:28         ` Mike Kravetz
2020-01-15  5:23           ` Yang Shi
2020-01-15  7:36             ` Li Xinhai
2020-01-15 17:16               ` Yang Shi
2020-01-15 21:07       ` Mike Kravetz
2020-01-15 21:30         ` Yang Shi
2020-01-15 21:45           ` Mike Kravetz
2020-01-15 21:59             ` Yang Shi
2020-01-16  8:07               ` HORIGUCHI NAOYA(堀口　直也)
2020-01-16 15:32                 ` Li Xinhai
2020-01-16  7:59         ` Michal Hocko
2020-01-16 19:22           ` Mike Kravetz
2020-01-17  2:32             ` Yang Shi
2020-01-17  2:38             ` Li Xinhai
2020-01-17  7:57               ` Michal Hocko
2020-01-17 12:05                 ` Li Xinhai
2020-01-17 15:20                   ` Michal Hocko
2020-01-17 15:46                     ` Li Xinhai
2020-01-20 12:45                       ` Michal Hocko
2020-01-21 14:15                         ` Li Xinhai
2020-01-21 14:53                           ` Michal Hocko
2020-01-22 13:55                             ` Li Xinhai
2020-01-14 19:12 ` [PATCH 1/2] mm/mempolicy: Checking hstate for hugetlbfs page in vma_migratable Mike Kravetz
2020-01-15  1:25 ` Andrew Morton

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