Re: [PATCH] memcg: vmalloc: simplify MEMCG_VMALLOC updates

[Johannes Weiner]

On Wed, Apr 02, 2025 at 10:33:26PM -0700, Shakeel Butt wrote:
> The vmalloc region can either be charged to a single memcg or none. At
> the moment kernel traverses all the pages backing the vmalloc region to
> update the MEMCG_VMALLOC stat. However there is no need to look at all
> the pages as all those pages will be charged to a single memcg or none.
> Simplify the MEMCG_VMALLOC update by just looking at the first page of
> the vmalloc region.
> 
> Signed-off-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>

It's definitely pointless to handle each page with the stat being
per-cgroup only. But I do wonder why it's not a regular vmstat item.

There is no real reason it *should* be a private memcg stat, is there?