diff mbox series

[4/6] mm/mm_init.c: remove meaningless calculation of zone->managed_pages in free_area_init_core()

Message ID 20240318142138.783350-5-bhe@redhat.com (mailing list archive)
State New
Headers show
Series mm/mm_init.c: refactor free_area_init_core() | expand

Commit Message

Baoquan He March 18, 2024, 2:21 p.m. UTC
Currently, in free_area_init_core(), when initialize zone's field, a
rough value is set to zone->managed_pages. That value is calculated by
(zone->present_pages - memmap_pages).

In the meantime, add the value to nr_all_pages and nr_kernel_pages which
represent all free pages of system (only low memory or including HIGHMEM
memory separately). Both of them are gonna be used in
alloc_large_system_hash().

However, the rough calculation and setting of zone->managed_pages is
meaningless because
  a) memmap pages are allocated on units of node in sparse_init() or
     alloc_node_mem_map(pgdat); The simple (zone->present_pages -
     memmap_pages) is too rough to make sense for zone;
  b) the set zone->managed_pages will be zeroed out and reset with
     acutal value in mem_init() via memblock_free_all(). Before the
     resetting, no buddy allocation request is issued.

Here, remove the meaningless and complicated calculation of
(zone->present_pages - memmap_pages), directly set zone->present_pages to
zone->managed_pages. It will be adjusted in mem_init().

And also remove the assignment of nr_all_pages and nr_kernel_pages in
free_area_init_core(). Instead, call the newly added calc_nr_kernel_pages()
to count up all free but not reserved memory in memblock and assign to
nr_all_pages and nr_kernel_pages. The counting excludes memmap_pages,
and other kernel used data, which is more accurate than old way and
simpler, and can also cover the ppc required arch_reserved_kernel_pages()
case.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
 mm/mm_init.c | 38 ++++++--------------------------------
 1 file changed, 6 insertions(+), 32 deletions(-)

Comments

Mike Rapoport March 19, 2024, 4:17 p.m. UTC | #1
On Mon, Mar 18, 2024 at 10:21:36PM +0800, Baoquan He wrote:
> Currently, in free_area_init_core(), when initialize zone's field, a
> rough value is set to zone->managed_pages. That value is calculated by
> (zone->present_pages - memmap_pages).
> 
> In the meantime, add the value to nr_all_pages and nr_kernel_pages which
> represent all free pages of system (only low memory or including HIGHMEM
> memory separately). Both of them are gonna be used in
> alloc_large_system_hash().
> 
> However, the rough calculation and setting of zone->managed_pages is
> meaningless because
>   a) memmap pages are allocated on units of node in sparse_init() or
>      alloc_node_mem_map(pgdat); The simple (zone->present_pages -
>      memmap_pages) is too rough to make sense for zone;
>   b) the set zone->managed_pages will be zeroed out and reset with
>      acutal value in mem_init() via memblock_free_all(). Before the
>      resetting, no buddy allocation request is issued.
> 
> Here, remove the meaningless and complicated calculation of
> (zone->present_pages - memmap_pages), directly set zone->present_pages to
> zone->managed_pages. It will be adjusted in mem_init().

Do you mean "set zone->managed_pages to zone->present_pages"?

I think we can just set zone->managed_pages to 0 in free_area_init_core().
Anyway it will be reset before the first use.
 
> And also remove the assignment of nr_all_pages and nr_kernel_pages in
> free_area_init_core(). Instead, call the newly added calc_nr_kernel_pages()
> to count up all free but not reserved memory in memblock and assign to
> nr_all_pages and nr_kernel_pages. The counting excludes memmap_pages,
> and other kernel used data, which is more accurate than old way and
> simpler, and can also cover the ppc required arch_reserved_kernel_pages()
> case.
> 
> Signed-off-by: Baoquan He <bhe@redhat.com>
> ---
>  mm/mm_init.c | 38 ++++++--------------------------------
>  1 file changed, 6 insertions(+), 32 deletions(-)
> 
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index c57a7fc97a16..55a2b886b7a6 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -1584,41 +1584,14 @@ static void __init free_area_init_core(struct pglist_data *pgdat)
>  
>  	for (j = 0; j < MAX_NR_ZONES; j++) {
>  		struct zone *zone = pgdat->node_zones + j;
> -		unsigned long size, freesize, memmap_pages;
> -
> -		size = zone->spanned_pages;
> -		freesize = zone->present_pages;
> -
> -		/*
> -		 * Adjust freesize so that it accounts for how much memory
> -		 * is used by this zone for memmap. This affects the watermark
> -		 * and per-cpu initialisations
> -		 */
> -		memmap_pages = calc_memmap_size(size, freesize);
> -		if (!is_highmem_idx(j)) {
> -			if (freesize >= memmap_pages) {
> -				freesize -= memmap_pages;
> -				if (memmap_pages)
> -					pr_debug("  %s zone: %lu pages used for memmap\n",
> -						 zone_names[j], memmap_pages);
> -			} else
> -				pr_warn("  %s zone: %lu memmap pages exceeds freesize %lu\n",
> -					zone_names[j], memmap_pages, freesize);
> -		}
> -
> -		if (!is_highmem_idx(j))
> -			nr_kernel_pages += freesize;
> -		/* Charge for highmem memmap if there are enough kernel pages */
> -		else if (nr_kernel_pages > memmap_pages * 2)
> -			nr_kernel_pages -= memmap_pages;
> -		nr_all_pages += freesize;
> +		unsigned long size = zone->spanned_pages;
>  
>  		/*
> -		 * Set an approximate value for lowmem here, it will be adjusted
> -		 * when the bootmem allocator frees pages into the buddy system.
> -		 * And all highmem pages will be managed by the buddy system.
> +		 * Set the zone->managed_pages as zone->present_pages roughly, it
> +		 * be zeroed out and reset when memblock allocator frees pages into
> +		 * buddy system.
>  		 */
> -		zone_init_internals(zone, j, nid, freesize);
> +		zone_init_internals(zone, j, nid, zone->present_pages);
>  
>  		if (!size)
>  			continue;
> @@ -1915,6 +1888,7 @@ void __init free_area_init(unsigned long *max_zone_pfn)
>  		check_for_memory(pgdat);
>  	}
>  
> +	calc_nr_kernel_pages();
>  	memmap_init();
>  
>  	/* disable hash distribution for systems with a single node */
> -- 
> 2.41.0
>
Baoquan He March 20, 2024, 8:18 a.m. UTC | #2
On 03/19/24 at 06:17pm, Mike Rapoport wrote:
> On Mon, Mar 18, 2024 at 10:21:36PM +0800, Baoquan He wrote:
> > Currently, in free_area_init_core(), when initialize zone's field, a
> > rough value is set to zone->managed_pages. That value is calculated by
> > (zone->present_pages - memmap_pages).
> > 
> > In the meantime, add the value to nr_all_pages and nr_kernel_pages which
> > represent all free pages of system (only low memory or including HIGHMEM
> > memory separately). Both of them are gonna be used in
> > alloc_large_system_hash().
> > 
> > However, the rough calculation and setting of zone->managed_pages is
> > meaningless because
> >   a) memmap pages are allocated on units of node in sparse_init() or
> >      alloc_node_mem_map(pgdat); The simple (zone->present_pages -
> >      memmap_pages) is too rough to make sense for zone;
> >   b) the set zone->managed_pages will be zeroed out and reset with
> >      acutal value in mem_init() via memblock_free_all(). Before the
> >      resetting, no buddy allocation request is issued.
> > 
> > Here, remove the meaningless and complicated calculation of
> > (zone->present_pages - memmap_pages), directly set zone->present_pages to
> > zone->managed_pages. It will be adjusted in mem_init().
> 
> Do you mean "set zone->managed_pages to zone->present_pages"?

Hmm, maybe 'set zone->managed_pages as zone->present_pages'
            or 
           'assign zone->present_pages to zone->managed_pages'
which is more precise.

Wwill update.

> 
> I think we can just set zone->managed_pages to 0 in free_area_init_core().
> Anyway it will be reset before the first use.

Yeah, setting to 0 is also fine. I thougt of 0 ever. Considering
zone->present_pages is closer value to actual zone->managed_pages
than 0, and it may be needed in the future in some way before
mem_init(). If no strong objection, I will keep the assigning
'zone->present_pages' to 'zone->managed_pages'.

Thanks again for careful reviewing.
Baoquan He March 20, 2024, 8:47 a.m. UTC | #3
On 03/20/24 at 04:18pm, Baoquan He wrote:
> On 03/19/24 at 06:17pm, Mike Rapoport wrote:
> > On Mon, Mar 18, 2024 at 10:21:36PM +0800, Baoquan He wrote:
> > > Currently, in free_area_init_core(), when initialize zone's field, a
> > > rough value is set to zone->managed_pages. That value is calculated by
> > > (zone->present_pages - memmap_pages).
> > > 
> > > In the meantime, add the value to nr_all_pages and nr_kernel_pages which
> > > represent all free pages of system (only low memory or including HIGHMEM
> > > memory separately). Both of them are gonna be used in
> > > alloc_large_system_hash().
> > > 
> > > However, the rough calculation and setting of zone->managed_pages is
> > > meaningless because
> > >   a) memmap pages are allocated on units of node in sparse_init() or
> > >      alloc_node_mem_map(pgdat); The simple (zone->present_pages -
> > >      memmap_pages) is too rough to make sense for zone;
> > >   b) the set zone->managed_pages will be zeroed out and reset with
> > >      acutal value in mem_init() via memblock_free_all(). Before the
> > >      resetting, no buddy allocation request is issued.
> > > 
> > > Here, remove the meaningless and complicated calculation of
> > > (zone->present_pages - memmap_pages), directly set zone->present_pages to
> > > zone->managed_pages. It will be adjusted in mem_init().
> > 
> > Do you mean "set zone->managed_pages to zone->present_pages"?
> 
> Hmm, maybe 'set zone->managed_pages as zone->present_pages'
>             or 
>            'assign zone->present_pages to zone->managed_pages'
> which is more precise.
> 
> Wwill update.
> 
> > 
> > I think we can just set zone->managed_pages to 0 in free_area_init_core().
> > Anyway it will be reset before the first use.

Rethink about this, it's better to set zone->managed_pages to 0 because
there isn't any page added to buddy. Will update.

> 
> Yeah, setting to 0 is also fine. I thougt of 0 ever. Considering
> zone->present_pages is closer value to actual zone->managed_pages
> than 0, and it may be needed in the future in some way before
> mem_init(). If no strong objection, I will keep the assigning
> 'zone->present_pages' to 'zone->managed_pages'.
> 
> Thanks again for careful reviewing.
>
diff mbox series

Patch

diff --git a/mm/mm_init.c b/mm/mm_init.c
index c57a7fc97a16..55a2b886b7a6 100644
--- a/mm/mm_init.c
+++ b/mm/mm_init.c
@@ -1584,41 +1584,14 @@  static void __init free_area_init_core(struct pglist_data *pgdat)
 
 	for (j = 0; j < MAX_NR_ZONES; j++) {
 		struct zone *zone = pgdat->node_zones + j;
-		unsigned long size, freesize, memmap_pages;
-
-		size = zone->spanned_pages;
-		freesize = zone->present_pages;
-
-		/*
-		 * Adjust freesize so that it accounts for how much memory
-		 * is used by this zone for memmap. This affects the watermark
-		 * and per-cpu initialisations
-		 */
-		memmap_pages = calc_memmap_size(size, freesize);
-		if (!is_highmem_idx(j)) {
-			if (freesize >= memmap_pages) {
-				freesize -= memmap_pages;
-				if (memmap_pages)
-					pr_debug("  %s zone: %lu pages used for memmap\n",
-						 zone_names[j], memmap_pages);
-			} else
-				pr_warn("  %s zone: %lu memmap pages exceeds freesize %lu\n",
-					zone_names[j], memmap_pages, freesize);
-		}
-
-		if (!is_highmem_idx(j))
-			nr_kernel_pages += freesize;
-		/* Charge for highmem memmap if there are enough kernel pages */
-		else if (nr_kernel_pages > memmap_pages * 2)
-			nr_kernel_pages -= memmap_pages;
-		nr_all_pages += freesize;
+		unsigned long size = zone->spanned_pages;
 
 		/*
-		 * Set an approximate value for lowmem here, it will be adjusted
-		 * when the bootmem allocator frees pages into the buddy system.
-		 * And all highmem pages will be managed by the buddy system.
+		 * Set the zone->managed_pages as zone->present_pages roughly, it
+		 * be zeroed out and reset when memblock allocator frees pages into
+		 * buddy system.
 		 */
-		zone_init_internals(zone, j, nid, freesize);
+		zone_init_internals(zone, j, nid, zone->present_pages);
 
 		if (!size)
 			continue;
@@ -1915,6 +1888,7 @@  void __init free_area_init(unsigned long *max_zone_pfn)
 		check_for_memory(pgdat);
 	}
 
+	calc_nr_kernel_pages();
 	memmap_init();
 
 	/* disable hash distribution for systems with a single node */