linux-kernel - Re: [PATCH 04/11] mm/hugetlb: unify hugetlb migration callback function

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Message-ID: <CAAmzW4Nv7H_MTD2NoKF3aOCDhETrdKA_VGPxNF+6zTfYY3aq3A@mail.gmail.com>
Date:   Fri, 22 May 2020 16:38:59 +0900
From:   Joonsoo Kim <js1304@...il.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>
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>,
        Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
        Michal Hocko <mhocko@...e.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH 04/11] mm/hugetlb: unify hugetlb migration callback function

2020년 5월 22일 (금) 오전 5:54, Mike Kravetz <mike.kravetz@...cle.com>님이 작성:
>
> On 5/17/20 6:20 PM, js1304@...il.com wrote:
> > From: Joonsoo Kim <iamjoonsoo.kim@....com>
> >
> > There is no difference between two migration callback functions,
> > alloc_huge_page_node() and alloc_huge_page_nodemask(), except
> > __GFP_THISNODE handling. This patch adds one more field on to
> > the alloc_control and handles this exception.
> >
> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
> > ---
> >  include/linux/hugetlb.h |  8 --------
> >  mm/hugetlb.c            | 23 ++---------------------
> >  mm/internal.h           |  1 +
> >  mm/mempolicy.c          |  3 ++-
> >  4 files changed, 5 insertions(+), 30 deletions(-)
> >
> > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> > index 6da217e..4892ed3 100644
> > --- a/include/linux/hugetlb.h
> > +++ b/include/linux/hugetlb.h
> > @@ -505,8 +505,6 @@ struct huge_bootmem_page {
> >
> >  struct page *alloc_migrate_huge_page(struct hstate *h,
> >                               struct alloc_control *ac);
> > -struct page *alloc_huge_page_node(struct hstate *h,
> > -                             struct alloc_control *ac);
> >  struct page *alloc_huge_page_nodemask(struct hstate *h,
> >                               struct alloc_control *ac);
> >  struct page *alloc_huge_page_vma(struct hstate *h, struct vm_area_struct *vma,
> > @@ -755,12 +753,6 @@ static inline void huge_ptep_modify_prot_commit(struct vm_area_struct *vma,
> >  struct hstate {};
> >
> >  static inline struct page *
> > -alloc_huge_page_node(struct hstate *h, struct alloc_control *ac)
> > -{
> > -     return NULL;
> > -}
> > -
> > -static inline struct page *
> >  alloc_huge_page_nodemask(struct hstate *h, struct alloc_control *ac)
> >  {
> >       return NULL;
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > index 859dba4..60b0983 100644
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -1981,31 +1981,12 @@ struct page *alloc_buddy_huge_page_with_mpol(struct hstate *h,
> >  }
> >
> >  /* page migration callback function */
> > -struct page *alloc_huge_page_node(struct hstate *h,
> > -                             struct alloc_control *ac)
> > -{
> > -     struct page *page = NULL;
> > -
> > -     ac->gfp_mask |= htlb_alloc_mask(h);
> > -     if (ac->nid != NUMA_NO_NODE)
> > -             ac->gfp_mask |= __GFP_THISNODE;
> > -
> > -     spin_lock(&hugetlb_lock);
> > -     if (h->free_huge_pages - h->resv_huge_pages > 0)
> > -             page = dequeue_huge_page_nodemask(h, ac);
> > -     spin_unlock(&hugetlb_lock);
> > -
> > -     if (!page)
> > -             page = alloc_migrate_huge_page(h, ac);
> > -
> > -     return page;
> > -}
> > -
> > -/* page migration callback function */
> >  struct page *alloc_huge_page_nodemask(struct hstate *h,
> >                               struct alloc_control *ac)
> >  {
> >       ac->gfp_mask |= htlb_alloc_mask(h);
> > +     if (ac->thisnode && ac->nid != NUMA_NO_NODE)
> > +             ac->gfp_mask |= __GFP_THISNODE;
> >
> >       spin_lock(&hugetlb_lock);
> >       if (h->free_huge_pages - h->resv_huge_pages > 0) {
> > diff --git a/mm/internal.h b/mm/internal.h
> > index 75b3f8e..574722d0 100644
> > --- a/mm/internal.h
> > +++ b/mm/internal.h
> > @@ -618,6 +618,7 @@ struct alloc_control {
> >       int nid;
> >       nodemask_t *nmask;
> >       gfp_t gfp_mask;
> > +     bool thisnode;
>
> I wonder if the new field is necessary?
>
> IIUC, it simply prevents the check for NUMA_NO_NODE and possible setting
> of __GFP_THISNODE in previous alloc_huge_page_nodemask() calling sequences.
> However, it appears that node (preferred_nid) is always set to something
> other than NUMA_NO_NODE in those callers.

Okay. I will check it.

> It obviously makes sense to add the field to guarantee no changes to
> functionality while making the conversions.  However, it it is not really
> necessary then it may cause confusion later.

Agreed.

Thanks.