linux-kernel - Re: [PATCH v3] mm/sparse.c: Use kvmalloc_node/kvfree to alloc/free memmap for the classic sparse

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Date:   Sat, 14 Mar 2020 08:53:34 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     linux-kernel@...r.kernel.org, willy@...radead.org,
        linux-mm@...ck.org, akpm@...ux-foundation.org, david@...hat.com,
        richard.weiyang@...il.com
Subject: Re: [PATCH v3] mm/sparse.c: Use kvmalloc_node/kvfree to alloc/free
 memmap for the classic sparse

On 03/13/20 at 03:56pm, Michal Hocko wrote:
> On Thu 12-03-20 22:17:49, Baoquan He wrote:
> > This change makes populate_section_memmap()/depopulate_section_memmap
> > much simpler.
> 
> Not only and you should make it more explicit. It also tries to allocate
> memmaps from the target numa node so this is a functional change. I
> would prefer to have that in a separate patch in case we hit some weird
> NUMA setups which would choke on memory less nodes and similar horrors.

Yes, splitting sounds more reasonable, I would love to do that. One
question is I noticed Andrew had picked this into -mm tree, if I post a
new patchset including these two small patches, whether it's convenient
to drop the old one and get these two merged.

Sorry, I don't know very well how this works in mm maintaining.

> 
> > Suggested-by: Michal Hocko <mhocko@...nel.org>
> > Signed-off-by: Baoquan He <bhe@...hat.com>
> 
> I do not see any reason this shouldn't work. Btw. did you get to test
> it?
> 
> Feel free to add
> Acked-by: Michal Hocko <mhocko@...e.com>
> to both patches if you go and split.
> 
> > ---
> > v2->v3:
> >   Remove __GFP_NOWARN and use array_size when calling kvmalloc_node()
> >   per Matthew's comments.
> > 
> >  mm/sparse.c | 27 +++------------------------
> >  1 file changed, 3 insertions(+), 24 deletions(-)
> > 
> > diff --git a/mm/sparse.c b/mm/sparse.c
> > index bf6c00a28045..bb99633575b5 100644
> > --- a/mm/sparse.c
> > +++ b/mm/sparse.c
> > @@ -734,35 +734,14 @@ static void free_map_bootmem(struct page *memmap)
> >  struct page * __meminit populate_section_memmap(unsigned long pfn,
> >  		unsigned long nr_pages, int nid, struct vmem_altmap *altmap)
> >  {
> > -	struct page *page, *ret;
> > -	unsigned long memmap_size = sizeof(struct page) * PAGES_PER_SECTION;
> > -
> > -	page = alloc_pages(GFP_KERNEL|__GFP_NOWARN, get_order(memmap_size));
> > -	if (page)
> > -		goto got_map_page;
> > -
> > -	ret = vmalloc(memmap_size);
> > -	if (ret)
> > -		goto got_map_ptr;
> > -
> > -	return NULL;
> > -got_map_page:
> > -	ret = (struct page *)pfn_to_kaddr(page_to_pfn(page));
> > -got_map_ptr:
> > -
> > -	return ret;
> > +	return kvmalloc_node(array_size(sizeof(struct page),
> > +			PAGES_PER_SECTION), GFP_KERNEL, nid);
> >  }
> >  
> >  static void depopulate_section_memmap(unsigned long pfn, unsigned long nr_pages,
> >  		struct vmem_altmap *altmap)
> >  {
> > -	struct page *memmap = pfn_to_page(pfn);
> > -
> > -	if (is_vmalloc_addr(memmap))
> > -		vfree(memmap);
> > -	else
> > -		free_pages((unsigned long)memmap,
> > -			   get_order(sizeof(struct page) * PAGES_PER_SECTION));
> > +	kvfree(pfn_to_page(pfn));
> >  }
> >  
> >  static void free_map_bootmem(struct page *memmap)
> > -- 
> > 2.17.2
> > 
> 
> -- 
> Michal Hocko
> SUSE Labs
>