Re: [PATCH v2 2/2] drm/msm/gem: Add modparam to disable shrinker blocking

[Konrad Dybcio]

On 9/12/26 4:59 PM, Rob Clark wrote:
> Normally if we are under enough memory pressure, the shrinker will
> eventually start waiting for BOs to become idle.  In some very latency
> sensitive use-cases this is undesirable.
> 
> Signed-off-by: Rob Clark <robin.clark@xxxxxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/msm/msm_gem_shrinker.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/msm_gem_shrinker.c b/drivers/gpu/drm/msm/msm_gem_shrinker.c
> index 3514d5c84989..83ee032cb21d 100644
> --- a/drivers/gpu/drm/msm/msm_gem_shrinker.c
> +++ b/drivers/gpu/drm/msm/msm_gem_shrinker.c
> @@ -19,6 +19,10 @@ static bool enable_eviction = true;
>  MODULE_PARM_DESC(enable_eviction, "Enable swappable GEM buffers");
>  module_param(enable_eviction, bool, 0600);
>  
> +static bool eviction_can_block = true;
> +MODULE_PARM_DESC(eviction_can_block, "Enable blocking for GEM buffer to become idle for eviction");
> +module_param(eviction_can_block, bool, 0600);
> +
>  static bool can_swap(void)
>  {
>  	return enable_eviction && get_nr_swap_pages() > 0;
> @@ -26,6 +30,8 @@ static bool can_swap(void)
>  
>  static bool can_block(struct shrink_control *sc)
>  {
> +	if (!eviction_can_block)
> +		return false;
>  	return (sc->gfp_mask & __GFP_DIRECT_RECLAIM) ||
>  	       (current_is_kswapd() && (sc->gfp_mask & __GFP_KSWAPD_RECLAIM));
>  }

This is just a guess, but can we always keep both and jump out
of msm_gem_shrinker_scan() early if we can satistfy nr_to_scan
without locking?

Konrad