Re: [PATCH 2/3] mm/page_alloc: move the kswapd node skip check into a helper

[SJ Park]

On Fri, 13 Nov 2026 15:52:35 -0800 Joshua Hahn <joshua.hahnjy@xxxxxxxxx> wrote:

> get_page_from_freelist() checks many conditions for each zone, often
> with a big comment block explaining the conditions.
> 
> Move the kswapd check and its comment into should_skip_kswapd_zone() to
> make the zone iteration cleaner to read.
> 
> While moving this, also resolve a checkpatch warning which complains of
> a waitqueue_active() call with no corresponding comment explaining why
> the lockless use is OK in this case.
> 
> No functional change intended.

Looks correct to me.

> 
> Signed-off-by: Joshua Hahn <joshua.hahnjy@xxxxxxxxx>

Reviewed-by: SJ Park <sj@xxxxxxxxxx>

[...]
> @@ -3865,22 +3885,10 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
>  			}
>  		}
>  
> -		/*
> -		 * If kswapd is already active on a node and the zone is below
> -		 * its kswapd watermark for this request, keep looking for
> -		 * other nodes that might be idle. This can happen if another
> -		 * process has NUMA bindings and is causing kswapd wakeups on
> -		 * only some nodes. Avoid accidental "node_reclaim_mode"-like
> -		 * behavior in this case.
> -		 */
>  		if (skip_kswapd_nodes &&
> -		    !waitqueue_active(&zone->zone_pgdat->kswapd_wait)) {
> -			mark = wmark_pages(zone, kswapd_watermark);
> -			if (!zone_watermark_fast(zone, order, mark,
> -					ac->highest_zoneidx, 0)) {
> -				skipped_kswapd_nodes = true;
> -				continue;
> -			}
> +		    should_skip_kswapd_zone(zone, order, ac)) {
> +			skipped_kswapd_nodes = true;
> +			continue;

Just thinking loud.  While reviewing I realized this patch is not based on
mm-new but apparently mm/page_alloc.git for-next.  I should also update some of
my setups.


Thanks,
SJ

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