Re: [PATCH v2 3/4] memcg: int16_t for cached slab stats

[Muchun Song]

> On May 22, 2026, at 09:19, Shakeel Butt <shakeel.butt@xxxxxxxxx> wrote:
> 
> Currently struct obj_stock_pcp stores cached slab stats in 'int' which
> is 4 bytes per counter on 64-bit machines. Switch them to int16_t to
> shrink the cached metadata.
> 
> The existing PAGE_SIZE flush in __account_obj_stock() bounds *bytes at
> PAGE_SIZE on 4KiB and 16KiB page archs, well within int16_t. On 64KiB
> pages PAGE_SIZE is well above S16_MAX so that flush never fires, and a
> sufficiently long run of accumulations would overflow the cache. Add
> an explicit S16_MAX guard before each add: when the next add would
> push abs(*bytes) past S16_MAX, fold the cached value into @nr and
> flush directly via mod_objcg_mlstate() before the accumulation.
> 
> Fixes: 01b9da291c49 ("mm: memcontrol: convert objcg to be per-memcg per-node type")
> Tested-by: kernel test robot <oliver.sang@xxxxxxxxx>
> Signed-off-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
> Reviewed-by: Harry Yoo (Oracle) <harry@xxxxxxxxxx>

Acked-by: Muchun Song <muchun.song@xxxxxxxxx>

Thanks.