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

[Vasily Gorbik <gor@linux.ibm.com>]

On Tue, Jun 18, 2024 at 11:57:19AM +0200, David Hildenbrand wrote:
> 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>

Applied, thanks!