Re: [PATCH 20/40] autonuma: alloc/free/init mm_autonuma

[Andrea Arcangeli <aarcange@redhat.com>]

On Sat, Jun 30, 2012 at 01:12:18AM -0400, Konrad Rzeszutek Wilk wrote:
> On Thu, Jun 28, 2012 at 02:56:00PM +0200, Andrea Arcangeli wrote:
> > This is where the mm_autonuma structure is being handled. Just like
> > sched_autonuma, this is only allocated at runtime if the hardware the
> > kernel is running on has been detected as NUMA. On not NUMA hardware
> 
> I think the correct wording is "non-NUMA", not "not NUMA".

That sounds far too easy to me, but I've no idea what's the right is here.

> > the memory cost is reduced to one pointer per mm.
> > 
> > To get rid of the pointer in the each mm, the kernel can be compiled
> > with CONFIG_AUTONUMA=n.
> > 
> > Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
> > ---
> >  kernel/fork.c |    7 +++++++
> >  1 files changed, 7 insertions(+), 0 deletions(-)
> > 
> > diff --git a/kernel/fork.c b/kernel/fork.c
> > index 0adbe09..3e5a0d9 100644
> > --- a/kernel/fork.c
> > +++ b/kernel/fork.c
> > @@ -527,6 +527,8 @@ static void mm_init_aio(struct mm_struct *mm)
> >  
> >  static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
> >  {
> > +	if (unlikely(alloc_mm_autonuma(mm)))
> > +		goto out_free_mm;
> 
> So reading that I would think that on non-NUMA machines this would fail
> (since there is nothing to allocate). But that is not the case
> (I hope!?) Perhaps just make the function not return any values?

It doesn't fail, it returns 0 on non-NUMA. It's identical to
alloc_task_autonuma, per prev email.