Re: [PATCH v2] mm: show_mem: show number of zspages in show_free_areas

[Johannes Weiner <hannes@cmpxchg.org>]

On Tue, Sep 02, 2025 at 09:49:21AM -0300, Thadeu Lima de Souza Cascardo wrote:
> When OOM is triggered, it will show where the pages might be for each zone.
> When using zram or zswap, it might look like lots of pages are missing.
> After this patch, zspages are shown as below.
> 
> [   48.792859] Node 0 DMA free:2812kB boost:0kB min:60kB low:72kB high:84kB reserved_highatomic:0KB free_highatomic:0KB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB zspages:11160kB present:15992kB managed:15360kB mlocked:0kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
> [   48.792962] lowmem_reserve[]: 0 956 956 956 956
> [   48.792988] Node 0 DMA32 free:3512kB boost:0kB min:3912kB low:4888kB high:5864kB reserved_highatomic:0KB free_highatomic:0KB active_anon:0kB inactive_anon:28kB active_file:8kB inactive_file:16kB unevictable:0kB writepending:0kB zspages:916780kB present:1032064kB managed:978944kB mlocked:0kB bounce:0kB free_pcp:500kB local_pcp:248kB free_cma:0kB
> [   48.793118] lowmem_reserve[]: 0 0 0 0 0
> 
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

> @@ -310,6 +310,7 @@ static void show_free_areas(unsigned int filter, nodemask_t *nodemask, int max_z
>  			" inactive_file:%lukB"
>  			" unevictable:%lukB"
>  			" writepending:%lukB"
> +			" zspages:%lukB"
>  			" present:%lukB"
>  			" managed:%lukB"
>  			" mlocked:%lukB"
> @@ -332,6 +333,11 @@ static void show_free_areas(unsigned int filter, nodemask_t *nodemask, int max_z
>  			K(zone_page_state(zone, NR_ZONE_INACTIVE_FILE)),
>  			K(zone_page_state(zone, NR_ZONE_UNEVICTABLE)),
>  			K(zone_page_state(zone, NR_ZONE_WRITE_PENDING)),
> +#if IS_ENABLED(CONFIG_ZSMALLOC)
> +			K(zone_page_state(zone, NR_ZSPAGES)),
> +#else
> +			0UL,
> +#endif
>  			K(zone->present_pages),
>  			K(zone_managed_pages(zone)),
>  			K(zone_page_state(zone, NR_MLOCK)),

Longer-term, it might make sense to simply iterate enum zone_stat_item
and enum node_stat_item and print them all.