Re: [PATCH 1/4] drm/panthor: Add freed_sz parameter to reclaim_priv_bos

[Steven Price]

On 06/05/2026 11:45, Nicolas Frattaroli wrote:
> panthor_mmu_reclaim_priv_bos returns the number of freed pages. However,
> how many bytes of freed memory this translates to can't generally be
> deduced from the number of pages, as the page size is a per-VM property.
> 
> It may be useful to know the exact number of bytes that have been freed

The "useful" aspect seems to just be a drm_dbg() message from what I can
see with this series? Am I missing something or is it not actually that
useful?

Thanks,
Steve

> for observability and debugging purposes. To that end, add a new
> parameter "freed_sz", which is a pointer to a size_t where this
> information will be stored. It may be NULL, in which case the
> information isn't stored at all.
> 
> Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@xxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/panthor/panthor_gem.c |  3 ++-
>  drivers/gpu/drm/panthor/panthor_mmu.c | 12 ++++++++++--
>  drivers/gpu/drm/panthor/panthor_mmu.h |  1 +
>  3 files changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c
> index 13295d7a593d..80e82238f3c5 100644
> --- a/drivers/gpu/drm/panthor/panthor_gem.c
> +++ b/drivers/gpu/drm/panthor/panthor_gem.c
> @@ -1511,7 +1511,8 @@ panthor_gem_shrinker_scan(struct shrinker *shrinker, struct shrink_control *sc)
>  		goto out;
>  
>  	freed += panthor_mmu_reclaim_priv_bos(ptdev, sc->nr_to_scan - freed,
> -					      &remaining, panthor_gem_try_evict);
> +					      &remaining, NULL,
> +					      panthor_gem_try_evict);
>  	if (freed >= sc->nr_to_scan)
>  		goto out;
>  
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c b/drivers/gpu/drm/panthor/panthor_mmu.c
> index a7ee14986849..b81388b35a58 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.c
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.c
> @@ -3127,13 +3127,18 @@ int panthor_vm_prepare_mapped_bos_resvs(struct drm_exec *exec, struct panthor_vm
>  unsigned long
>  panthor_mmu_reclaim_priv_bos(struct panthor_device *ptdev,
>  			     unsigned int nr_to_scan, unsigned long *remaining,
> +			     size_t *freed_sz,
>  			     bool (*shrink)(struct drm_gem_object *,
>  					    struct ww_acquire_ctx *))
>  {
> +	unsigned long newly_freed;
>  	unsigned long freed = 0;
>  	LIST_HEAD(remaining_vms);
>  	LIST_HEAD(vms);
>  
> +	if (freed_sz)
> +		*freed_sz = 0;
> +
>  	mutex_lock(&ptdev->reclaim.lock);
>  	list_splice_init(&ptdev->reclaim.vms, &vms);
>  
> @@ -3152,8 +3157,11 @@ panthor_mmu_reclaim_priv_bos(struct panthor_device *ptdev,
>  
>  		mutex_unlock(&ptdev->reclaim.lock);
>  
> -		freed += drm_gem_lru_scan(&vm->reclaim.lru, nr_to_scan - freed,
> -					  remaining, shrink, NULL);
> +		newly_freed = drm_gem_lru_scan(&vm->reclaim.lru, nr_to_scan - freed,
> +					       remaining, shrink, NULL);
> +		if (freed_sz)
> +			*freed_sz += panthor_vm_page_size(vm) * newly_freed;
> +		freed += newly_freed;
>  
>  		mutex_lock(&ptdev->reclaim.lock);
>  
> diff --git a/drivers/gpu/drm/panthor/panthor_mmu.h b/drivers/gpu/drm/panthor/panthor_mmu.h
> index 3522fbbce369..12b18b5f90e1 100644
> --- a/drivers/gpu/drm/panthor/panthor_mmu.h
> +++ b/drivers/gpu/drm/panthor/panthor_mmu.h
> @@ -52,6 +52,7 @@ int panthor_vm_evict_bo_mappings_locked(struct panthor_gem_object *bo);
>  unsigned long
>  panthor_mmu_reclaim_priv_bos(struct panthor_device *ptdev,
>  			     unsigned int nr_to_scan, unsigned long *remaining,
> +			     size_t *freed_sz,
>  			     bool (*shrink)(struct drm_gem_object *,
>  					    struct ww_acquire_ctx *));
>  int panthor_vm_prepare_mapped_bos_resvs(struct drm_exec *exec,
>