linux-kernel - Re: [PATCH v2 03/12] mm/hugetlb: introduce alloc_control structure to simplify migration target allocation APIs

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Date:   Wed, 10 Jun 2020 12:07:17 +0900
From:   Joonsoo Kim <js1304@...il.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>, kernel-team@....com,
        Vlastimil Babka <vbabka@...e.cz>,
        Christoph Hellwig <hch@...radead.org>,
        Roman Gushchin <guro@...com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH v2 03/12] mm/hugetlb: introduce alloc_control structure to
 simplify migration target allocation APIs

2020년 6월 9일 (화) 오후 10:24, Michal Hocko <mhocko@...nel.org>님이 작성:
>
> On Wed 27-05-20 15:44:54, Joonsoo Kim wrote:
> > From: Joonsoo Kim <iamjoonsoo.kim@....com>
> >
> > Currently, page allocation functions for migration requires some arguments.
> > More worse, in the following patch, more argument will be needed to unify
> > the similar functions. To simplify them, in this patch, unified data
> > structure that controls allocation behaviour is introduced.
> >
> > For clean-up, function declarations are re-ordered.
>
> This is really hard to review without having a clear picture of the
> resulting code so bear with me. I can see some reasons why allocation
> callbacks might benefit from a agragated argument but you seem to touch
> the internal hugetlb dequeue_huge_page_vma which shouldn't really need
> that. I wouldn't mind much but I remember the hugetlb allocation
> functions layering is quite complex for hugetlb specific reasons (see
> 0c397daea1d4 ("mm, hugetlb: further simplify hugetlb allocation API")
> for more background).
>
> Is there any reason why the agregated argument cannot be limited only to
> migration callbacks. That would be alloc_huge_page_node, alloc_huge_page_nodemask
> and alloc_huge_page_vma.

I did it since it's simple for me, but, yes, it's not good to touch
the internal functions.

Anyway, Vlastimil already suggested not to introduce alloc_control for
any hugetlb
functions. I will try it on the next version so the next version would not have
alloc_control in any hugetlb functions.

Thanks.