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

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Message-ID: <20200313145619.GD21007@dhcp22.suse.cz>
Date:   Fri, 13 Mar 2020 15:56:19 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Baoquan He <bhe@...hat.com>
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 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.

> 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