linux-kernel - Re: [PATCH 3/5] mm/sparse: move mem_sections allocation out of memory

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Message-ID: <CAA+hA=TZyVcSfbBzJvzwULhbvfC00JP=_xam3JoirdnTiDd_KQ@mail.gmail.com>
Date:   Tue, 18 May 2021 18:45:08 +0800
From:   Dong Aisheng <dongas86@...il.com>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     Dong Aisheng <aisheng.dong@....com>, linux-mm@...ck.org,
        open list <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 3/5] mm/sparse: move mem_sections allocation out of memory_present()

On Tue, May 18, 2021 at 6:12 PM Mike Rapoport <rppt@...nel.org> wrote:
>
> On Mon, May 17, 2021 at 07:20:42PM +0800, Dong Aisheng wrote:
> > The only path to call memory_present() is from memblocks_present().
> > The struct mem_section **mem_section only needs to be initialized once,
> > so no need put the initialization/allocation code in memory_present()
> > which will be called multiple times for each section.
> >
> > After moving, the 'unlikely' condition statement becomes to be
> > meaningless as it's only initialized one time, so dropped as well.
> >
> > Cc: Andrew Morton <akpm@...ux-foundation.org>
> > Signed-off-by: Dong Aisheng <aisheng.dong@....com>
> > ---
> >  mm/sparse.c | 23 ++++++++++-------------
> >  1 file changed, 10 insertions(+), 13 deletions(-)
> >
> > diff --git a/mm/sparse.c b/mm/sparse.c
> > index 98bfacc763da..df4418c12f04 100644
> > --- a/mm/sparse.c
> > +++ b/mm/sparse.c
> > @@ -254,19 +254,6 @@ static void __init memory_present(int nid, unsigned long start, unsigned long en
> >  {
> >       unsigned long pfn;
> >
> > -#ifdef CONFIG_SPARSEMEM_EXTREME
> > -     if (unlikely(!mem_section)) {
> > -             unsigned long size, align;
> > -
> > -             size = sizeof(struct mem_section *) * NR_SECTION_ROOTS;
> > -             align = 1 << (INTERNODE_CACHE_SHIFT);
> > -             mem_section = memblock_alloc(size, align);
> > -             if (!mem_section)
> > -                     panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
> > -                           __func__, size, align);
> > -     }
> > -#endif
>
> Maybe split this into a helper function and call it directly from
> sparse_init()?
>

Sounds good to me
e.g. sparse_alloc_section_root() called directly from sparse_init().
Thanks for the suggestion

Regards
Aisheng

> > -
> >       start &= PAGE_SECTION_MASK;
> >       mminit_validate_memmodel_limits(&start, &end);
> >       for (pfn = start; pfn < end; pfn += PAGES_PER_SECTION) {
> > @@ -292,9 +279,19 @@ static void __init memory_present(int nid, unsigned long start, unsigned long en
> >   */
> >  static void __init memblocks_present(void)
> >  {
> > +     unsigned long __maybe_unused size, align;
> >       unsigned long start, end;
> >       int i, nid;
> >
> > +#ifdef CONFIG_SPARSEMEM_EXTREME
> > +     size = sizeof(struct mem_section *) * NR_SECTION_ROOTS;
> > +     align = 1 << (INTERNODE_CACHE_SHIFT);
> > +     mem_section = memblock_alloc(size, align);
> > +     if (!mem_section)
> > +             panic("%s: Failed to allocate %lu bytes align=0x%lx\n",
> > +                   __func__, size, align);
> > +#endif
> > +
> >       for_each_mem_pfn_range(i, MAX_NUMNODES, &start, &end, &nid)
> >               memory_present(nid, start, end);
> >  }
> > --
> > 2.25.1
> >
> >
>
> --
> Sincerely yours,
> Mike.