Re: [PATCH] Docs/admin-guide/cgroup-v2: fix memory.stat doc details

[Michal Koutný]

On Mon, Jun 22, 2026 at 05:26:53PM +0200, Doehyun Baek <doehyunbaek@xxxxxxxxx> wrote:
> However, both zswapped and zswap_incomp are memory_stats[] entries, so
> memory.stat prints them through memcg_page_state_output(). Since
> MEMCG_ZSWAP_INCOMP is not special-cased as a raw count, the stored page
> count is multiplied by the default PAGE_SIZE unit and exported as bytes.
> 
>     unsigned long memcg_page_state_output(struct mem_cgroup *memcg, int item)
>     {
>         return memcg_page_state(memcg, item) *
>         memcg_page_state_output_unit(item);
>     }

Ah, I messed up how memcg_page_state_output_unit() is used. The printed
values are amounts (in bytes).

> Separately, this matches the existing documentation style for zswapped,
> whose exported value is described as a memory amount:
> 
>     zswapped
>         Amount of application memory swapped out to zswap.
> 
> Since zswap_incomp follows the same memory.stat output path, I think its
> documentation should describe the exported value as a memory amount too.
> 
> I also boot-tested this in QEMU with the current tree and zswap enabled.
> With incompressible pages pushed into zswap, memory.stat showed:
> 
>     zswap 87822336
>     zswapped 87822336
>     zswap_incomp 87822336

Thanks for the test and for the fix!

> 
> The zswap_incomp value there is byte-valued; it is not a plain page
> count. It also matches zswapped in this all-incompressible case, which
> is consistent with both being exported as memory amounts.

Acked-by: Michal Koutný <mkoutny@xxxxxxxx>

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