Re: [PATCH v1 9/9] drm/panthor: Add a GEM shrinker

[Boris Brezillon <boris.brezillon@collabora.com>]

On Thu, 15 Jan 2026 13:56:42 +0000
Akash Goel <akash.goel@arm.com> wrote:


> > +static unsigned long
> > +panthor_gem_shrinker_count(struct shrinker *shrinker, struct shrink_control *sc)
> > +{
> > +	struct panthor_device *ptdev = shrinker->private_data;
> > +	unsigned long count;
> > +
> > +	/* We currently don't have a flag to tell when the content of a
> > +	 * BO can be discarded.
> > +	 */
> > +	if (!can_swap())
> > +		return 0;
> > +
> > +	count = ptdev->reclaim.unused.count;
> > +	count += ptdev->reclaim.mmapped.count;
> > +
> > +	if (can_block(sc))
> > +		count += ptdev->reclaim.gpu_mapped_count;
> > +  
> 
> Should we do like this
> 
> 	return count ? count : SHRINK_EMPTY;
> 
> 
> Other drivers are also doing the same
> 
> https://elixir.bootlin.com/linux/v6.18.4/source/drivers/gpu/drm/xe/xe_shrinker.c#L156 
> 
> 
> https://elixir.bootlin.com/linux/v6.18.4/source/drivers/gpu/drm/ttm/ttm_pool.c#L1160
> 
> https://elixir.bootlin.com/linux/v6.18.4/source/mm/vmalloc.c#L5245
> 
> It might matter if CONFIG_MEMCG is set.

Absolutely. I'll fix that in v2.

> 
> > +	return count;
> > +}

> >   /**
> > @@ -678,6 +689,16 @@ int panthor_vm_active(struct panthor_vm *vm)
> >   	if (refcount_inc_not_zero(&vm->as.active_cnt))
> >   		goto out_dev_exit;
> >   
> > +	/* As soon as active is called, we place the VM as the end of the VM LRU.  
> 
> 
> Please replace 'as the end' with 'at the end'.

Will do.