On Sat, Apr 3, 2021 at 3:17 AM Dan Schatzberg <[email protected]> wrote:
>
> set_active_memcg() worked for kernel allocations but was silently
> ignored for user pages.
>
> This patch establishes a precedence order for who gets charged:
>
> 1. If there is a memcg associated with the page already, that memcg is
>    charged. This happens during swapin.
>
> 2. If an explicit mm is passed, mm->memcg is charged. This happens
>    during page faults, which can be triggered in remote VMs (eg gup).
>
> 3. Otherwise consult the current process context. If there is an
>    active_memcg, use that. Otherwise, current->mm->memcg.
>
> Previously, if a NULL mm was passed to mem_cgroup_charge (case 3) it
> would always charge the root cgroup. Now it looks up the active_memcg
> first (falling back to charging the root cgroup if not set).
>
> Signed-off-by: Dan Schatzberg <[email protected]>
> Acked-by: Johannes Weiner <[email protected]>
> Acked-by: Tejun Heo <[email protected]>
> Acked-by: Chris Down <[email protected]>
> Reviewed-by: Shakeel Butt <[email protected]>

Reviewed-by: Muchun Song <[email protected]>

Thanks.

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