Re: [PATCH 3/3] mm/mm_init.c: not always search next deferred_init_pfn from very beginning

[Mike Rapoport <rppt@kernel.org>]

On Fri, May 31, 2024 at 12:26:13AM +0000, Wei Yang wrote:
> In function deferred_init_memmap(), we call
> deferred_init_mem_pfn_range_in_zone() to get the next deferred_init_pfn.
> But we always search it from the very beginning.
> 
> Since we save the index in i, we can leverage this to search from i next
> time.
> 
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> ---
>  include/linux/memblock.h | 19 -------------------
>  mm/mm_init.c             | 21 ++++++++++++---------
>  2 files changed, 12 insertions(+), 28 deletions(-)
> 
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index 6cf18dc2b4d0..45cac33334c8 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -299,25 +299,6 @@ void __next_mem_pfn_range(int *idx, int nid, unsigned long *out_start_pfn,
>  void __next_mem_pfn_range_in_zone(u64 *idx, struct zone *zone,
>  				  unsigned long *out_spfn,
>  				  unsigned long *out_epfn);
> -/**
> - * for_each_free_mem_pfn_range_in_zone - iterate through zone specific free
> - * memblock areas
> - * @i: u64 used as loop variable
> - * @zone: zone in which all of the memory blocks reside
> - * @p_start: ptr to phys_addr_t for start address of the range, can be %NULL
> - * @p_end: ptr to phys_addr_t for end address of the range, can be %NULL
> - *
> - * Walks over free (memory && !reserved) areas of memblock in a specific
> - * zone. Available once memblock and an empty zone is initialized. The main
> - * assumption is that the zone start, end, and pgdat have been associated.
> - * This way we can use the zone to determine NUMA node, and if a given part
> - * of the memblock is valid for the zone.
> - */
> -#define for_each_free_mem_pfn_range_in_zone(i, zone, p_start, p_end)	\
> -	for (i = 0,							\
> -	     __next_mem_pfn_range_in_zone(&i, zone, p_start, p_end);	\
> -	     i != U64_MAX;					\
> -	     __next_mem_pfn_range_in_zone(&i, zone, p_start, p_end))
>  
>  /**
>   * for_each_free_mem_pfn_range_in_zone_from - iterate through zone specific
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index d05a4c38310f..ec17bf93f946 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -2023,18 +2023,21 @@ static unsigned long  __init deferred_init_pages(struct zone *zone,
>   * return false indicating there are no valid ranges left.
>   */
>  static bool __init
> -deferred_init_mem_pfn_range_in_zone(u64 *i, struct zone *zone,
> +deferred_init_mem_pfn_range_in_zone_from(u64 *i, struct zone *zone,

I don't think renaming this function is useful.
The comment above it, on the other hand, needs update.

>  				    unsigned long *spfn, unsigned long *epfn,
>  				    unsigned long first_init_pfn)
>  {
> -	u64 j;
> +	u64 j = *i;
> +
> +	if (j == 0)
> +		__next_mem_pfn_range_in_zone(&j, zone, spfn, epfn);
>  
>  	/*
>  	 * Start out by walking through the ranges in this zone that have
>  	 * already been initialized. We don't need to do anything with them
>  	 * so we just need to flush them out of the system.
>  	 */
> -	for_each_free_mem_pfn_range_in_zone(j, zone, spfn, epfn) {
> +	for_each_free_mem_pfn_range_in_zone_from(j, zone, spfn, epfn) {
>  		if (*epfn <= first_init_pfn)
>  			continue;
>  		if (*spfn < first_init_pfn)
> @@ -2106,9 +2109,9 @@ deferred_init_memmap_chunk(unsigned long start_pfn, unsigned long end_pfn,
>  {
>  	unsigned long spfn, epfn;
>  	struct zone *zone = arg;
> -	u64 i;
> +	u64 i = 0;
>  
> -	deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn, start_pfn);
> +	deferred_init_mem_pfn_range_in_zone_from(&i, zone, &spfn, &epfn, start_pfn);
>  
>  	/*
>  	 * Initialize and free pages in MAX_PAGE_ORDER sized increments so that
> @@ -2137,7 +2140,7 @@ static int __init deferred_init_memmap(void *data)
>  	unsigned long start = jiffies;
>  	struct zone *zone;
>  	int max_threads;
> -	u64 i;
> +	u64 i = 0;
>  
>  	/* Bind memory initialisation thread to a local node if possible */
>  	if (!cpumask_empty(cpumask))
> @@ -2168,7 +2171,7 @@ static int __init deferred_init_memmap(void *data)
>  
>  	max_threads = deferred_page_init_max_threads(cpumask);
>  
> -	while (deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn, first_init_pfn)) {
> +	while (deferred_init_mem_pfn_range_in_zone_from(&i, zone, &spfn, &epfn, first_init_pfn)) {
>  		first_init_pfn = ALIGN(epfn, PAGES_PER_SECTION);
>  		struct padata_mt_job job = {
>  			.thread_fn   = deferred_init_memmap_chunk,
> @@ -2212,7 +2215,7 @@ bool __init deferred_grow_zone(struct zone *zone, unsigned int order)
>  	unsigned long first_deferred_pfn = pgdat->first_deferred_pfn;
>  	unsigned long spfn, epfn, flags;
>  	unsigned long nr_pages = 0;
> -	u64 i;
> +	u64 i = 0;
>  
>  	/* Only the last zone may have deferred pages */
>  	if (zone_end_pfn(zone) != pgdat_end_pfn(pgdat))
> @@ -2230,7 +2233,7 @@ bool __init deferred_grow_zone(struct zone *zone, unsigned int order)
>  	}
>  
>  	/* If the zone is empty somebody else may have cleared out the zone */
> -	if (!deferred_init_mem_pfn_range_in_zone(&i, zone, &spfn, &epfn,
> +	if (!deferred_init_mem_pfn_range_in_zone_from(&i, zone, &spfn, &epfn,
>  						 first_deferred_pfn)) {
>  		pgdat->first_deferred_pfn = ULONG_MAX;
>  		pgdat_resize_unlock(pgdat, &flags);
> -- 
> 2.34.1
> 

-- 
Sincerely yours,
Mike.