Re: [PATCH v4 3/6] drm/ttm: Issue direct reclaim at beneficial_order

["Christian König" <christian.koenig@amd.com>]

On 4/30/26 21:18, Matthew Brost wrote:
> Triggering kswap at an order higher than beneficial_order makes little
> sense, as the driver has already indicated the optimal order at which
> reclaim is effective. Similarly, issuing direct reclaim or triggering
> kswap at a lower order than beneficial_order is ineffective, since the
> driver does not benefit from reclaiming lower-order pages.
> 
> As a result, direct reclaim should only be issued with __GFP_NORETRY at
> exactly beneficial_order, or as a fallback, direct reclaim without
> __GFP_NORETRY at order 0 when failure is not an option.
> 
> Cc: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Cc: Carlos Santa <carlos.santa@intel.com>
> Cc: Christian Koenig <christian.koenig@amd.com>
> Cc: Huang Rui <ray.huang@amd.com>
> Cc: Matthew Auld <matthew.auld@intel.com>
> Cc: Matthew Brost <matthew.brost@intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Maxime Ripard <mripard@kernel.org>
> Cc: Thomas Zimmermann <tzimmermann@suse.de>
> Cc: David Airlie <airlied@gmail.com>
> Cc: Simona Vetter <simona@ffwll.ch>
> CC: dri-devel@lists.freedesktop.org
> Cc: Daniel Colascione <dancol@dancol.org>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> Reviewed-by: Christian Koenig <christian.koenig@amd.com>
> Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
> ---
>  drivers/gpu/drm/ttm/ttm_pool.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
> index 26a3689e5fd9..8425dbcc6c68 100644
> --- a/drivers/gpu/drm/ttm/ttm_pool.c
> +++ b/drivers/gpu/drm/ttm/ttm_pool.c
> @@ -165,8 +165,8 @@ static struct page *ttm_pool_alloc_page(struct ttm_pool *pool, gfp_t gfp_flags,
>  	 * Do not add latency to the allocation path for allocations orders
>  	 * device tolds us do not bring them additional performance gains.
>  	 */
> -	if (beneficial_order && order > beneficial_order)
> -		gfp_flags &= ~__GFP_DIRECT_RECLAIM;
> +	if (order && beneficial_order && order != beneficial_order)
> +		gfp_flags &= ~__GFP_RECLAIM;

Just one additional nit: The subject line says "direct reclaim" but we disable both direct as well as kswapd based reclaim.

Potentially just update the subject line.

Regards,
Christian.

>  
>  	if (!ttm_pool_uses_dma_alloc(pool)) {
>  		p = alloc_pages_node(pool->nid, gfp_flags, order);