Re: [PATCH] xen/gntdev: Grant maps should not be subject to NUMA balancing

[Boris Ostrovsky]

On 11/10/2015 02:36 PM, Konrad Rzeszutek Wilk wrote:
> On Tue, Nov 10, 2015 at 02:22:44PM -0500, Boris Ostrovsky wrote:
> > Doing so will cause the grant to be unmapped and then, during
> > fault handling, the fault to be mistakenly treated as NUMA hint
> > fault.
> >
> > In addition, even if we those maps could partcipate in NUMA
> > balancing it wouldn't provide any benefit since we wouldn't be
> > able to determine physical page's node (even if/when VNUMA is
> > implemented).
> >
> > Marking grant maps' VMAs as VM_IO will exclude them from being
> > part of NUMA balancing.
> Should this be 'cc:stable@xxxxxxxxxxxxxxx' ?

This bug becomes a real problem with 4.4, now that NUMA balancing is on 
by default.

But we should probably include it in stable too. I'll resubmit it then 
with CC tag.

-boris

> > Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> > ---
> >   drivers/xen/gntdev.c |    2 +-
> >   1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
> > index 67b9163..bf312df 100644
> > --- a/drivers/xen/gntdev.c
> > +++ b/drivers/xen/gntdev.c
> > @@ -802,7 +802,7 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
> >   
> >   	vma->vm_ops = &gntdev_vmops;
> >   
> > -	vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
> > +	vma->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP | VM_IO;
> >   
> >   	if (use_ptemod)
> >   		vma->vm_flags |= VM_DONTCOPY;
> > --
> > 1.7.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/