[PATCH v2 2/2] drm/ttm: Increase pool shrinker batch target

[Christian König]

On 6/3/25 13:27, Tvrtko Ursulin wrote:
> The default core shrink target of 128 pages (SHRINK_BATCH) is quite low
> relative to how cheap TTM pool shrinking is, and how the free pages are
> distributed in page order pools.
> 
> We can make the target a bit more aggressive by making it roughly the
> average number of pages across all pools, freeing more of the cached
> pages every time shrinker core invokes our callback.
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at igalia.com>
> Cc: Christian König <christian.koenig at amd.com>
> Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> ---
>  drivers/gpu/drm/ttm/ttm_pool.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/ttm/ttm_pool.c b/drivers/gpu/drm/ttm/ttm_pool.c
> index c060c90b89c0..e671812789ea 100644
> --- a/drivers/gpu/drm/ttm/ttm_pool.c
> +++ b/drivers/gpu/drm/ttm/ttm_pool.c
> @@ -1265,10 +1265,16 @@ int ttm_pool_debugfs(struct ttm_pool *pool, struct seq_file *m)
>  }
>  EXPORT_SYMBOL(ttm_pool_debugfs);
>  
> +/* Free average pool number of pages.  */
> +#define TTM_SHRINKER_BATCH ((1 << (MAX_PAGE_ORDER / 2)) * NR_PAGE_ORDERS)

To be honest this feels random. But I can't come up with a better idea either and it still looks better than the default as far as I can see.

So feel free to add Reviewed-by: Christian König <christian.koenig at amd.com> to the series.

Should I push it to drm-misc-next or do you now have commit rights?

Regards,
Christian.

> +
>  /* Test the shrinker functions and dump the result */
>  static int ttm_pool_debugfs_shrink_show(struct seq_file *m, void *data)
>  {
> -	struct shrink_control sc = { .gfp_mask = GFP_NOFS };
> +	struct shrink_control sc = {
> +		.gfp_mask = GFP_NOFS,
> +		.nr_to_scan = TTM_SHRINKER_BATCH,
> +	};
>  
>  	fs_reclaim_acquire(GFP_KERNEL);
>  	seq_printf(m, "%lu/%lu\n", ttm_pool_shrinker_count(mm_shrinker, &sc),
> @@ -1326,6 +1332,7 @@ int ttm_pool_mgr_init(unsigned long num_pages)
>  
>  	mm_shrinker->count_objects = ttm_pool_shrinker_count;
>  	mm_shrinker->scan_objects = ttm_pool_shrinker_scan;
> +	mm_shrinker->batch = TTM_SHRINKER_BATCH;
>  	mm_shrinker->seeks = 1;
>  
>  	shrinker_register(mm_shrinker);