Re: [PATCH 3/3] drm/xe: Avoid shrinker reclaim from kswapd under fragmentation

["Thomas Hellström" <thomas.hellstrom@linux.intel.com>]

Hi,

On Mon, 2026-04-20 at 18:26 -0700, Matthew Brost wrote:
> When the Xe shrinker is invoked from kswapd, a large amount of free
> memory in ZONE_NORMAL relative to the high watermark is a strong
> signal
> that reclaim is being driven by fragmentation rather than true memory
> pressure.
> 
> In this case, shrinking Xe memory is unlikely to help kswapd make
> forward progress. Instead it can evict active GPU memory despite the
> system still having substantial free memory, increasing residency
> churn
> and reducing GPU forward progress.
> 
> Detect this case and bail out early from the Xe shrinker when running
> in
> kswapd and ZONE_NORMAL has more than 2x its high watermark free.
> 
> Cc: Thomas Hellström <thomas.hellstrom@linux.intel.com>
> Cc: Carlos Santa <carlos.santa@intel.com>
> Cc: Matthew Auld <matthew.auld@intel.com>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
> ---
>  drivers/gpu/drm/xe/xe_shrinker.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/gpu/drm/xe/xe_shrinker.c
> b/drivers/gpu/drm/xe/xe_shrinker.c
> index 83374cd57660..e56afde83de6 100644
> --- a/drivers/gpu/drm/xe/xe_shrinker.c
> +++ b/drivers/gpu/drm/xe/xe_shrinker.c
> @@ -236,6 +236,19 @@ static unsigned long xe_shrinker_scan(struct
> shrinker *shrink, struct shrink_con
>  	if (nr_scanned >= nr_to_scan || !can_backup)
>  		goto out;
>  
> +	if (current_is_kswapd()) {
> +		struct zone *zone = &NODE_DATA(sc->nid)-
> >node_zones[ZONE_NORMAL];
> +		unsigned long free_pages = zone_page_state(zone,
> NR_FREE_PAGES);
> +		unsigned long high_wmark = high_wmark_pages(zone);
> +
> +		/*
> +		 * If we have 2x the high watermark free, this is
> definitely
> +		 * fragmentation
> +		 */
> +		if (free_pages > (high_wmark * 2))
> +			goto out;
> +	}
> +

While this or a similar check might make sense, That should ideally be
in the TTM shrinker helpers. And probably we should ask core mm for a
proper indication whether this is indeed fragmentation-driven.

Thanks,
Thomas



>  	/* If we didn't wake before, try to do it now if needed. */
>  	if (!runtime_pm)
>  		runtime_pm = xe_shrinker_runtime_pm_get(shrinker,
> true, 0, can_backup);