Re: [PATCH] Factor in buddy allocator alignment requirements in nodememory alignment

[christoph]

On Mon, 16 May 2005, Dave Hansen wrote:

> On Mon, 2005-05-16 at 12:05 -0700, christoph wrote:
> > Memory for nodes on i386 is currently aligned on 2 MB boundaries.
> > However, the buddy allocator needs pages to be aligned on
> > PAGE_SIZE << MAX_ORDER which is 8MB if MAX_ORDER = 11.
> 
> Why do you need this?  Are you planning on allowing NUMA KVA remap pages
> to be handed over to the buddy allocator?  That would be a major
> departure from what we do now, and I'd be very interested in seeing how
> that is implemented before a infrastructure for it goes in.

Because the buddy allocator is complaining about wrongly allocated zones!

in page_alloc.c:

static void __init free_area_init_core(struct pglist_data *pgdat,
                unsigned long *zones_size, unsigned long *zholes_size)
{
...

  const unsigned long zone_required_alignment = 1UL << (MAX_ORDER-1);

...

             if ((zone_start_pfn) & (zone_required_alignment-1))
                        printk(KERN_CRIT "BUG: wrong zone alignment, it will crash\n");


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