Re: [PATCH] x86: numa: drop ZONE_ALIGN

David Rientjes
2014-06-10T22:10:01Z

On Mon, 9 Jun 2014, Luiz Capitulino wrote:

> > > > > diff --git a/arch/x86/include/asm/numa.h b/arch/x86/include/asm/numa.h
> > > > > index 4064aca..01b493e 100644
> > > > > --- a/arch/x86/include/asm/numa.h
> > > > > +++ b/arch/x86/include/asm/numa.h
> > > > > @@ -9,7 +9,6 @@
> > > > > #ifdef CONFIG_NUMA
> > > > >
> > > > > #define NR_NODE_MEMBLKS (MAX_NUMNODES*2)
> > > > > -#define ZONE_ALIGN (1UL << (MAX_ORDER+PAGE_SHIFT))
> > > > >
> > > > > /*
> > > > > * Too small node sizes may confuse the VM badly. Usually they
> > > > > diff --git a/arch/x86/mm/numa.c b/arch/x86/mm/numa.c
> > > > > index 1d045f9..69f6362 100644
> > > > > --- a/arch/x86/mm/numa.c
> > > > > +++ b/arch/x86/mm/numa.c
> > > > > @@ -200,8 +200,6 @@ static void __init setup_node_data(int nid, u64 start, u64 end)
> > > > > if (end && (end - start) < NODE_MIN_SIZE)
> > > > > return;
> > > > >
> > > > > - start = roundup(start, ZONE_ALIGN);
> > > > > -
> > > > > printk(KERN_INFO "Initmem setup node %d [mem %#010Lx-%#010Lx]\n",
> > > > > nid, start, end - 1);
> > > > >
> > > >
> > > > What ensures this start address is page aligned from the BIOS?
> > >
> > > To which start address do you refer to?
> >
> > The start address displayed in the dmesg is not page aligned anymore with
> > your change, correct?
>
> I have to check that but I don't expect this to happen because my
> understanding of the code is that what's rounded up here is just discarded
> in free_area_init_node(). Am I wrong?
>

NODE_DATA(nid)->node_start_pfn needs to be accurate if
node_set_online(nid). Since there is no guarantee about page alignment
from the ACPI spec, removing the roundup() entirely could cause the
address shift >> PAGE_SIZE to be off by one. I, like you, do not see the
need for the ZONE_ALIGN above, but I think we agree that it should be
replaced with PAGE_SIZE instead.