linux-kernel - Re: [PATCH] mm: show_mem: show number of zspages in show_free

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Message-Id: <20250902014933.93741-1-sj@kernel.org>
Date: Mon,  1 Sep 2025 18:49:33 -0700
From: SeongJae Park <sj@...nel.org>
To: Thadeu Lima de Souza Cascardo <cascardo@...lia.com>
Cc: SeongJae Park <sj@...nel.org>,
	linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Vlastimil Babka <vbabka@...e.cz>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Michal Hocko <mhocko@...e.com>,
	Brendan Jackman <jackmanb@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Zi Yan <ziy@...dia.com>,
	kernel-dev@...lia.com
Subject: Re: [PATCH] mm: show_mem: show number of zspages in show_free_areas

Hello,

On Mon,  1 Sep 2025 15:37:28 -0300 Thadeu Lima de Souza Cascardo <cascardo@...lia.com> wrote:

> When OOM is triggered, it will show where the pages might be for each zone.
> When using zram, it might look like lots of pages are missing. After this
> patch, zspages are shown as below.
[...]
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@...lia.com>
> ---
>  mm/show_mem.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/mm/show_mem.c b/mm/show_mem.c
> index 41999e94a56d..ecf20a93ea54 100644
> --- a/mm/show_mem.c
> +++ b/mm/show_mem.c
> @@ -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 +333,7 @@ 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)),
> +			K(zone_page_state(zone, NR_ZSPAGES)),

I found latest mm-new fails kunit's um build as below, and 'git bisect' points
this patch.

    $ make all compile_commands.json scripts_gdb ARCH=um O=.kunit --jobs=40
    ERROR:root:In file included from ../mm/show_mem.c:18:
    ../mm/show_mem.c: In function ‘show_free_areas’:
    ../mm/show_mem.c:336:49: error: ‘NR_ZSPAGES’ undeclared (first use in this function); did you mean ‘NR_STATS’?
      336 |                         K(zone_page_state(zone, NR_ZSPAGES)),
          |                                                 ^~~~~~~~~~
    [...]

Maybe some CONFIG_ZSMALLOC undeclard case handling, like below, is needed?

    --- a/mm/show_mem.c
    +++ b/mm/show_mem.c
    @@ -333,7 +333,9 @@ 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)),
    +#endif
                            K(zone->present_pages),
                            K(zone_managed_pages(zone)),
                            K(zone_page_state(zone, NR_MLOCK)),


Thanks,
SJ

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