linux-kernel - Re: [PATCH v5 2/4] mm/sparsemem: Defer the ms->section_mem

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Message-ID: <CAGM2reaS=KsD1OTxO9OYGdVuVyQb72ew=XQus2sJ-zAUbTAvpQ@mail.gmail.com>
Date:   Wed, 27 Jun 2018 23:11:35 -0400
From:   Pavel Tatashin <pasha.tatashin@...cle.com>
To:     bhe@...hat.com
Cc:     osalvador@...hadventures.net, LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        dave.hansen@...el.com, pagupta@...hat.com,
        Linux Memory Management List <linux-mm@...ck.org>,
        kirill.shutemov@...ux.intel.com
Subject: Re: [PATCH v5 2/4] mm/sparsemem: Defer the ms->section_mem_map clearing

Once you remove the ms mentioned by Oscar:
Reviewed-by: Pavel Tatashin <pasha.tatashin@...cle.com>
On Wed, Jun 27, 2018 at 6:59 PM Baoquan He <bhe@...hat.com> wrote:
>
> On 06/27/18 at 11:54am, Oscar Salvador wrote:
> > On Wed, Jun 27, 2018 at 09:31:14AM +0800, Baoquan He wrote:
> > > In sparse_init(), if CONFIG_SPARSEMEM_ALLOC_MEM_MAP_TOGETHER=y, system
> > > will allocate one continuous memory chunk for mem maps on one node and
> > > populate the relevant page tables to map memory section one by one. If
> > > fail to populate for a certain mem section, print warning and its
> > > ->section_mem_map will be cleared to cancel the marking of being present.
> > > Like this, the number of mem sections marked as present could become
> > > less during sparse_init() execution.
> > >
> > > Here just defer the ms->section_mem_map clearing if failed to populate
> > > its page tables until the last for_each_present_section_nr() loop. This
> > > is in preparation for later optimizing the mem map allocation.
> > >
> > > Signed-off-by: Baoquan He <bhe@...hat.com>
> > > ---
> > >  mm/sparse-vmemmap.c |  1 -
> > >  mm/sparse.c         | 12 ++++++++----
> > >  2 files changed, 8 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> > > index bd0276d5f66b..640e68f8324b 100644
> > > --- a/mm/sparse-vmemmap.c
> > > +++ b/mm/sparse-vmemmap.c
> > > @@ -303,7 +303,6 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
> > >             ms = __nr_to_section(pnum);
> > >             pr_err("%s: sparsemem memory map backing failed some memory will not be available\n",
> > >                    __func__);
> > > -           ms->section_mem_map = 0;
> >
> > Since we are deferring the clearing of section_mem_map, I guess we do not need
> >
> > struct mem_section *ms;
> > ms = __nr_to_section(pnum);
> >
> > anymore, right?
>
> Right, good catch, thanks.
>
> I will post a new round to fix this.
>
> >
> > >     }
> > >
> > >     if (vmemmap_buf_start) {
> > > diff --git a/mm/sparse.c b/mm/sparse.c
> > > index 6314303130b0..71ad53da2cd1 100644
> > > --- a/mm/sparse.c
> > > +++ b/mm/sparse.c
> > > @@ -451,7 +451,6 @@ void __init sparse_mem_maps_populate_node(struct page **map_map,
> > >             ms = __nr_to_section(pnum);
> > >             pr_err("%s: sparsemem memory map backing failed some memory will not be available\n",
> > >                    __func__);
> > > -           ms->section_mem_map = 0;
> >
> > The same goes here.
> >
> >
> >
> > --
> > Oscar Salvador
> > SUSE L3
>