Re: [PATCH] drm/ttm: Fix GPU MM stats during pool shrinking

[Kenneth Crudup <kenny@panix.com>]

On 5/1/26 15:30, Matthew Brost wrote:

> TTM pool shrinking frees pages by calling __free_pages() directly,
> which bypasses updates to NR_GPU_ACTIVE and leaves GPU MM accounting
> out of sync.
> 
> Introduce a helper, __free_pages_gpu_account(), and use it for all page
> frees in ttm_pool.c so GPU MM statistics are updated consistently.
> 
> Reported-by: Kenneth Crudup <kenny@panix.com>
> Fixes: ae80122f3896 ("drm/ttm: use gpu mm stats to track gpu memory allocations. (v4)")
> Cc: Christian Koenig <christian.koenig@amd.com>
> Cc: Huang Rui <ray.huang@amd.com>
> Cc: Matthew Auld <matthew.auld@intel.com>
> Cc: David Airlie <airlied@gmail.com>
> Cc: dri-devel@lists.freedesktop.org
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
>   drivers/gpu/drm/ttm/ttm_pool.c | 16 +++++++++++-----
>   1 file changed, 11 insertions(+), 5 deletions(-)

Tested-By: Kenneth R. Crudup <kenny@panix.com>

> diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
> index 26a3689e5fd9..95bbd9328072 100644
> --- a/drivers/gpu/drm/ttm/ttm_pool.c
> +++ b/drivers/gpu/drm/ttm/ttm_pool.c
> @@ -206,6 +206,14 @@ static struct page *ttm_pool_alloc_page(struct ttm_pool *pool, gfp_t gfp_flags,
>   	return NULL;
>   }
>   
> +static void __free_pages_gpu_account(struct page *p, unsigned int order,
> +				     bool reclaim)
> +{
> +	mod_lruvec_page_state(p, reclaim ? NR_GPU_RECLAIM : NR_GPU_ACTIVE,
> +			      -(1 << order));
> +	__free_pages(p, order);
> +}
> +
>   /* Reset the caching and pages of size 1 << order */
>   static void ttm_pool_free_page(struct ttm_pool *pool, enum ttm_caching caching,
>   			       unsigned int order, struct page *p, bool reclaim)
> @@ -223,9 +231,7 @@ static void ttm_pool_free_page(struct ttm_pool *pool, enum ttm_caching caching,
>   #endif
>   
>   	if (!pool || !ttm_pool_uses_dma_alloc(pool)) {
> -		mod_lruvec_page_state(p, reclaim ? NR_GPU_RECLAIM : NR_GPU_ACTIVE,
> -				      -(1 << order));
> -		__free_pages(p, order);
> +		__free_pages_gpu_account(p, order, reclaim);
>   		return;
>   	}
>   
> @@ -606,7 +612,7 @@ static int ttm_pool_restore_commit(struct ttm_pool_tt_restore *restore,
>   			 */
>   			ttm_pool_split_for_swap(restore->pool, p);
>   			copy_highpage(restore->alloced_page + i, p);
> -			__free_pages(p, 0);
> +			__free_pages_gpu_account(p, 0, false);
>   		}
>   
>   		restore->restored_pages++;
> @@ -1068,7 +1074,7 @@ long ttm_pool_backup(struct ttm_pool *pool, struct ttm_tt *tt,
>   			if (flags->purge) {
>   				shrunken += num_pages;
>   				page->private = 0;
> -				__free_pages(page, order);
> +				__free_pages_gpu_account(page, order, false);
>   				memset(tt->pages + i, 0,
>   				       num_pages * sizeof(*tt->pages));
>   			}

-- 
Kenneth R. Crudup / Sr. SW Engineer, Scott County Consulting, Orange 
County CA