Re: [PATCH 1/3] drm/etnaviv: don't trigger OOM killer when page allocation fails

[Lucas Stach <l.stach@pengutronix.de>]

Am Dienstag, den 20.06.2017, 11:06 +0200 schrieb Daniel Vetter:
> On Tue, Jun 06, 2017 at 09:17:06AM +0200, Lucas Stach wrote:
> > GPU buffers can be quite large, so userspace is expected to deal with
> > allocation failure. Don't trigger the OOM killer when page allocation for
> > the GEM objects fails, as this opens an easy possiblity for unprivileged
> > applications to DOS the system,a s the shmem pages are not fully accounted
> > to the allocating process.
> > 
> > Signed-off-by: Lucas Stach <dev@lynxeye.de>
> > ---
> >  drivers/gpu/drm/etnaviv/etnaviv_gem.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/etnaviv/etnaviv_gem.c b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> > index f0efc5d..4c53508 100644
> > --- a/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> > +++ b/drivers/gpu/drm/etnaviv/etnaviv_gem.c
> > @@ -662,7 +662,8 @@ static struct drm_gem_object *__etnaviv_gem_new(struct drm_device *dev,
> >  		 * going to pin these pages.
> >  		 */
> >  		mapping = obj->filp->f_mapping;
> > -		mapping_set_gfp_mask(mapping, GFP_HIGHUSER);
> > +		mapping_set_gfp_mask(mapping, GFP_HIGHUSER |
> > +				     __GFP_NORETRY | __GFP_NOWARN);
> 
> _NORETRY means the mm does try hard at all to free memory. We've just done
> this patch in 4.12 and totally regret it, because now gpu tasks run out of
> memory with plenty of (gpu) memory available that could be reaped.
> 
> There's some discussions going on with Michal Hocko and Chris Wilson
> about possible solutions for this without so much hacks.

Thanks for the heads up. In contrast to some of the other drivers
Etnaviv hasn't grown a proper shrinker yet, so I still think this patch
is a step in the right direction for the time being.
Currently with Etnaviv sitting on lots of GPU memory and the MM trying
hard to free more memory for GPU usage a simple piglit run might
pressure the OOM killer hard enough to bring the system down by killing
PID 1.

Regards,
Lucas

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