From: "Li Xinhai" <lixinhai.lxh@gmail.com>
To: anshuman.khandual <anshuman.khandual@arm.com>, 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: Mon, 20 Jan 2020 22:19:11 +0800 [thread overview]
Message-ID: <20200120221908768379320@gmail.com> (raw)
In-Reply-To: b9024406-7e80-3e17-d79f-395c3669b53f@arm.com
On 2020-01-20 at 17:51 Anshuman Khandual wrote:
>
>
>On 01/16/2020 08:48 PM, 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?
>
>unmap_and_move_hugepage() aborts migrating a HugeTLB page (from the list)
>if it's corresponding hstate does not support migration. IIUC the current
>proposal will enable early bail out and prevent migration via migrate_pages()
>at a much higher level like mbind() and other system calls if corresponding
>VMA is HugeTLB but it's hstate lacks migration support. This should probably
>save some cycles for HugeTLB VMAs.
Thanks for comments. Yes,this patch is for enable early bail out.
next prev parent reply other threads:[~2020-01-20 14:19 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-16 4:11 [PATCH v4] mm/mempolicy,hugetlb: Checking hstate for hugetlbfs page in vma_migratable 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
2020-01-17 3:16 ` Li Xinhai
2020-01-18 3:11 ` Li Xinhai
2020-01-18 15:27 ` Li Xinhai
2020-01-20 10:12 ` Michal Hocko
2020-01-20 15:37 ` Li Xinhai
2020-01-20 16:05 ` Michal Hocko
2020-01-21 3:42 ` Anshuman Khandual
2020-01-21 13:08 ` Li Xinhai
2020-01-21 12:44 ` Li Xinhai
2020-01-20 9:21 ` Anshuman Khandual
2020-01-20 11:32 ` Michal Hocko
2020-01-21 3:22 ` Anshuman Khandual
2020-01-20 14:19 ` Li Xinhai [this message]
2020-01-22 6:05 ` Anshuman Khandual
2020-01-22 13:21 ` Li Xinhai
2020-01-23 7:48 ` Anshuman Khandual
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