linux-kernel - Re: [PATCH] mm: thp: register mm for khugepaged when merging vma for shmem

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Message-ID: <be046d3f-06e0-09fd-c1d0-3e374dedcf16@linux.alibaba.com>
Date:   Thu, 21 Jun 2018 15:24:20 -0700
From:   Yang Shi <yang.shi@...ux.alibaba.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     hughd@...gle.com, kirill.shutemov@...ux.intel.com, vbabka@...e.cz,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: thp: register mm for khugepaged when merging vma for
 shmem



On 6/21/18 3:10 PM, Kirill A. Shutemov wrote:
> On Fri, Jun 22, 2018 at 05:40:47AM +0800, Yang Shi wrote:
>> When merging anonymous page vma, if the size of vam can fit in at least
> s/vam/vma/
>
>> one hugepage, the mm will be registered for khugepaged for collapsing
>> THP in the future.
>>
>> But, it skips shmem vma. Doing so for shmem too when merging vma in
>> order to increase the odd to collapse hugepage by khugepaged.
> Good catch. Thanks.
>
> I think the fix incomplete. We shouldn't require vma->anon_vma for shmem,
> only for anonymous mappings. We don't support file-private THPs.

So you mean, shmem_file(vma->vm_file) && PageAnon(page)?

>
>> Also increase the count of shmem THP collapse. It looks missed before.
> Separate patch, please.

Sure.

Thanks,
Yang

>