linux-kernel - Re: [PATCH 2/2] mm/vmscan: make sure wakeup

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Message-ID: <8735j2opd9.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date:   Mon, 28 Mar 2022 09:08:34 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Wei Yang <richard.weiyang@...il.com>
Cc:     akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, mgorman@...hsingularity.net
Subject: Re: [PATCH 2/2] mm/vmscan: make sure wakeup_kswapd with managed zone

Hi, Wei,

Wei Yang <richard.weiyang@...il.com> writes:

> wakeup_kswapd() only wake up kswapd when the zone is managed.
>
> For two callers of wakeup_kswapd(), they are node perspective.
>
>   * wake_all_kswapds
>   * numamigrate_isolate_page
>
> If we picked up a !managed zone, this is not we expected.
>
> This patch makes sure we pick up a managed zone for wakeup_kswapd().
>
> Signed-off-by: Wei Yang <richard.weiyang@...il.com>
> ---
>  mm/migrate.c    | 2 +-
>  mm/page_alloc.c | 2 ++
>  2 files changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 3d60823afd2d..c4b654c0bdf0 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -2046,7 +2046,7 @@ static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page)
>  		if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING))
>  			return 0;
>  		for (z = pgdat->nr_zones - 1; z >= 0; z--) {
> -			if (populated_zone(pgdat->node_zones + z))
> +			if (managed_zone(pgdat->node_zones + z))

This looks good to me!  Thanks!  It seems that we can replace
populated_zone() in migrate_balanced_pgdat() too.  Right?

>  				break;
>  		}
>  		wakeup_kswapd(pgdat->node_zones + z, 0, order, ZONE_MOVABLE);
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 4c0c4ef94ba0..6656c2d06e01 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4674,6 +4674,8 @@ static void wake_all_kswapds(unsigned int order, gfp_t gfp_mask,
>  
>  	for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, highest_zoneidx,
>  					ac->nodemask) {
> +		if (!managed_zone(zone))
> +			continue;
>  		if (last_pgdat != zone->zone_pgdat)
>  			wakeup_kswapd(zone, gfp_mask, order, highest_zoneidx);
>  		last_pgdat = zone->zone_pgdat;

Best Regards,
Huang, Ying