linux-kernel - Re: [PATCH v2 4/6] mm/mm_init.c: remove meaningless calculation of zone->managed_pages in free_area_init

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Message-ID: <ZgU9_zpuIOu2b_gT@kernel.org>
Date: Thu, 28 Mar 2024 11:53:03 +0200
From: Mike Rapoport <rppt@...nel.org>
To: Baoquan He <bhe@...hat.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, x86@...nel.org,
	linuxppc-dev@...ts.ozlabs.org, akpm@...ux-foundation.org
Subject: Re: [PATCH v2 4/6] mm/mm_init.c: remove meaningless calculation of
 zone->managed_pages in free_area_init_core()

On Thu, Mar 28, 2024 at 04:32:38PM +0800, Baoquan He wrote:
> On 03/25/24 at 10:56pm, Baoquan He wrote:
> >  
> >  		/*
> > -		 * 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.
> > +		 * Initialize zone->managed_pages as 0 , it will be reset
> > +		 * when memblock allocator frees pages into buddy system.
> >  		 */
> > -		zone_init_internals(zone, j, nid, freesize);
> > +		zone_init_internals(zone, j, nid, 0);
> 
> Here, we should initialize zone->managed_pages as zone->present_pages
> because later page_group_by_mobility_disabled need be set according to
> zone->managed_pages. Otherwise page_group_by_mobility_disabled will be
> set to 1 always. I will sent out v3.

With zone->managed_pages set to zone->present_pages we won't account for
the reserved memory for initialization of page_group_by_mobility_disabled.

As watermarks are still not initialized at the time build_all_zonelists()
is called, we may use nr_all_pages - nr_kernel_pages instead of
nr_free_zone_pages(), IMO.
 
> From a17b0921b4bd00596330f61ee9ea4b82386a9fed Mon Sep 17 00:00:00 2001
> From: Baoquan He <bhe@...hat.com>
> Date: Thu, 28 Mar 2024 16:20:15 +0800
> Subject: [PATCH] mm/mm_init.c: set zone's ->managed_pages as ->present_pages
>  for now
> Content-type: text/plain
> 
> Because page_group_by_mobility_disabled need be set according to zone's
> managed_pages later.
> 
> Signed-off-by: Baoquan He <bhe@...hat.com>
> ---
>  mm/mm_init.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/mm_init.c b/mm/mm_init.c
> index cc24e7958c0c..dd875f943cbb 100644
> --- a/mm/mm_init.c
> +++ b/mm/mm_init.c
> @@ -1561,7 +1561,7 @@ static void __init free_area_init_core(struct pglist_data *pgdat)
>  		 * Initialize zone->managed_pages as 0 , it will be reset
>  		 * when memblock allocator frees pages into buddy system.
>  		 */
> -		zone_init_internals(zone, j, nid, 0);
> +		zone_init_internals(zone, j, nid, zone->present_pages);
>  
>  		if (!size)
>  			continue;
> -- 
> 2.41.0
> 
> 
> >  
> >  		if (!size)
> >  			continue;
> > @@ -1915,6 +1878,7 @@ 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
> > 
> 

-- 
Sincerely yours,
Mike.