Re: [PATCH] s390/mm: get total ram pages from memblock

[David Hildenbrand <david@redhat.com>]

On 16.06.24 03:35, Wei Yang wrote:
> On s390, zero page's size relies on total ram pages.
> 
> Since we plan to move the accounting into __free_pages_core(),
> totalram_pages may not represent the total usable pages on system
> at this point when defer_init is enabled.
> 
> We can get the total usable pages from memblock directly. The size maybe
> not accurate due to the alignment, but enough for the calculation.
> 
> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> CC: Mike Rapoport (IBM) <rppt@kernel.org>
> CC: David Hildenbrand <david@redhat.com>
> 
> ---
> Not tested on a machine, hope it is fine.
> ---
>   arch/s390/mm/init.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
> index e769d2726f4e..d811ffa5e147 100644
> --- a/arch/s390/mm/init.c
> +++ b/arch/s390/mm/init.c
> @@ -65,12 +65,13 @@ static void __init setup_zero_pages(void)
>   	unsigned int order;
>   	struct page *page;
>   	int i;
> +	unsigned long total_pages = PHYS_PFN(memblock_phys_mem_size() - memblock_reserved_size());
>   
>   	/* Latest machines require a mapping granularity of 512KB */
>   	order = 7;
>   
>   	/* Limit number of empty zero pages for small memory sizes */
> -	while (order > 2 && (totalram_pages() >> 10) < (1UL << order))
> +	while (order > 2 && (total_pages >> 10) < (1UL << order))
>   		order--;
>   
>   	empty_zero_page = __get_free_pages(GFP_KERNEL | __GFP_ZERO, order);

I suspect that this is good enough as an approximation for that purpose.

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Cheers,

David / dhildenb