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From: Yang Shi <yang.shi@linux.alibaba.com>
To: Mike Kravetz <mike.kravetz@oracle.com>,
	Li Xinhai <lixinhai.lxh@gmail.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>
Cc: akpm <akpm@linux-foundation.org>, mhocko <mhocko@suse.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: Wed, 15 Jan 2020 13:59:14 -0800
Message-ID: <2d488bd7-0f2e-f691-b1b6-f2f1faec8ab4@linux.alibaba.com> (raw)
In-Reply-To: <52a03774-f6cd-c66b-6d27-ebf74aa7a850@oracle.com>



On 1/15/20 1:45 PM, Mike Kravetz wrote:
> On 1/15/20 1:30 PM, Yang Shi wrote:
>> On 1/15/20 1:07 PM, Mike Kravetz wrote:
>>> What should we do?
>>> ==================
>>> 1) Nothing more than optimizations by Li Xinhai.  Behavior that could be
>>>      seen as conflicting with man page has existed since v3.12 and I am
>>>      not aware of any complaints.
>>> 2) In addition to optimizations by Li Xinhai, modify code to truly ignore
>>>      MPOL_MF_STRICT for huge page mappings.  This would be fairly easy to do
>>>      after a failure of migrate_pages().  We could simply traverse the list
>>>      of pages that were not migrated looking for any non-hugetlb page.
>> I don't think we can do this easily since migrate_pages() would put the migration failed hugetlb pages back to hugepage_activelist so there should not any hugetlb page reside on the pagelist regardless of failure if I read the code correctly.
>>
> You are correct.  I made an assumption without actually looking at the code. :(
>
>> Other than that traversing page list to look for a certain type page doesn't sound scalable to me.
>>
>>> 3) Remove the statement "MPOL_MF_STRICT is ignored on huge page mappings."
>>>      and modify code accordingly.
>>>
>>> My suggestion would be for 1 or 2.  Thoughts?
>> By rethinking the history (thanks again for digging into it), it sounds #3 should be more reasonable. It sounds like the behavior was changed since hugetlb migration was added but the man page was not updated to reflect the change.
>>
> Let's hope Naoya comments.  My only concern with #3 is that we will be changing
> behavior.  I do not think many people (if any) depend on existing behavior.
> However, you can never be sure.

Yes, this would change the bahavior, but I don't see why we have to 
treat hugetlb specially nowadays with migration supported.




  reply index

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
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 [this message]
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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