Re: [PATCH] mm/mm_init.c: simplify logic of deferred_[init|free]_pages

[Mike Rapoport <rppt@kernel.org>]

On Wed, Jun 12, 2024 at 02:04:21AM +0000, Wei Yang wrote:
> Function deferred_[init|free]_pages are only used in
> deferred_init_maxorder(), which makes sure the range to init/free is
> within MAX_ORDER_NR_PAGES size.
> 
> With this knowledge, we can simplify these two functions. Since
> 
>   * only the first pfn could be IS_MAX_ORDER_ALIGNED()
> 
> Also since the range passed to deferred_[init|free]_pages is always from
> memblock.memory for those we have already allocated memmap to cover,
> pfn_valid() always return true. Then we can remove related check.
> 
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> CC: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> CC: Mike Rapoport (IBM) <rppt@kernel.org>
> CC: David Hildenbrand <david@redhat.com>

Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>

> ---
>  mm/mm_init.c | 63 +++++++---------------------------------------------
>  1 file changed, 8 insertions(+), 55 deletions(-)
> 
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index c152c60eca3d..63d70fc60705 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -1911,7 +1911,7 @@ unsigned long __init node_map_pfn_alignment(void)
>  }
>  
>  #ifdef CONFIG_DEFERRED_STRUCT_PAGE_INIT
> -static void __init deferred_free_range(unsigned long pfn,
> +static void __init deferred_free_pages(unsigned long pfn,
>  				       unsigned long nr_pages)
>  {
>  	struct page *page;
> @@ -1950,69 +1950,22 @@ static inline void __init pgdat_init_report_one_done(void)
>  		complete(&pgdat_init_all_done_comp);
>  }
>  
> -/*
> - * Returns true if page needs to be initialized or freed to buddy allocator.
> - *
> - * We check if a current MAX_PAGE_ORDER block is valid by only checking the
> - * validity of the head pfn.
> - */
> -static inline bool __init deferred_pfn_valid(unsigned long pfn)
> -{
> -	if (IS_MAX_ORDER_ALIGNED(pfn) && !pfn_valid(pfn))
> -		return false;
> -	return true;
> -}
> -
> -/*
> - * Free pages to buddy allocator. Try to free aligned pages in
> - * MAX_ORDER_NR_PAGES sizes.
> - */
> -static void __init deferred_free_pages(unsigned long pfn,
> -				       unsigned long end_pfn)
> -{
> -	unsigned long nr_free = 0;
> -
> -	for (; pfn < end_pfn; pfn++) {
> -		if (!deferred_pfn_valid(pfn)) {
> -			deferred_free_range(pfn - nr_free, nr_free);
> -			nr_free = 0;
> -		} else if (IS_MAX_ORDER_ALIGNED(pfn)) {
> -			deferred_free_range(pfn - nr_free, nr_free);
> -			nr_free = 1;
> -		} else {
> -			nr_free++;
> -		}
> -	}
> -	/* Free the last block of pages to allocator */
> -	deferred_free_range(pfn - nr_free, nr_free);
> -}
> -
>  /*
>   * Initialize struct pages.  We minimize pfn page lookups and scheduler checks
>   * by performing it only once every MAX_ORDER_NR_PAGES.
>   * Return number of pages initialized.
>   */
> -static unsigned long  __init deferred_init_pages(struct zone *zone,
> -						 unsigned long pfn,
> -						 unsigned long end_pfn)
> +static unsigned long __init deferred_init_pages(struct zone *zone,
> +						unsigned long pfn,
> +						unsigned long end_pfn)
>  {
>  	int nid = zone_to_nid(zone);
> -	unsigned long nr_pages = 0;
> +	unsigned long nr_pages = end_pfn - pfn;
>  	int zid = zone_idx(zone);
> -	struct page *page = NULL;
> +	struct page *page = pfn_to_page(pfn);
>  
> -	for (; pfn < end_pfn; pfn++) {
> -		if (!deferred_pfn_valid(pfn)) {
> -			page = NULL;
> -			continue;
> -		} else if (!page || IS_MAX_ORDER_ALIGNED(pfn)) {
> -			page = pfn_to_page(pfn);
> -		} else {
> -			page++;
> -		}
> +	for (; pfn < end_pfn; pfn++, page++)
>  		__init_single_page(page, pfn, zid, nid);
> -		nr_pages++;
> -	}
>  	return nr_pages;
>  }
>  
> @@ -2096,7 +2049,7 @@ deferred_init_maxorder(u64 *i, struct zone *zone, unsigned long *start_pfn,
>  			break;
>  
>  		t = min(mo_pfn, epfn);
> -		deferred_free_pages(spfn, t);
> +		deferred_free_pages(spfn, t - spfn);
>  
>  		if (mo_pfn <= epfn)
>  			break;
> -- 
> 2.34.1
> 

-- 
Sincerely yours,
Mike.