Re: [PATCH 2/4] mm: memcontrol: re-use global VM event enum

[Vladimir Davydov <vdavydov.dev@gmail.com>]

On Tue, Apr 04, 2017 at 06:01:46PM -0400, Johannes Weiner wrote:
> The current duplication is a high-maintenance mess, and it's painful
> to add new items.
> 
> This increases the size of the event array, but we'll eventually want
> most of the VM events tracked on a per-cgroup basis anyway.
> 
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Although the increase in the mem_cgroup struct introduced by this patch
looks scary, I agree this is a reasonable step toward unification of
vmstat, as most vm_even_item entries do make sense to be accounted per
cgroup as well.

Acked-by: Vladimir Davydov <vdavydov.dev@gmail.com>

> @@ -608,9 +601,9 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
>  
>  	/* pagein of a big page is an event. So, ignore page size */
>  	if (nr_pages > 0)
> -		__this_cpu_inc(memcg->stat->events[MEM_CGROUP_EVENTS_PGPGIN]);
> +		__this_cpu_inc(memcg->stat->events[PGPGIN]);
>  	else {
> -		__this_cpu_inc(memcg->stat->events[MEM_CGROUP_EVENTS_PGPGOUT]);
> +		__this_cpu_inc(memcg->stat->events[PGPGOUT]);
>  		nr_pages = -nr_pages; /* for event */
>  	}

AFAIR this doesn't exactly match system-wide PGPGIN/PGPGOUT: they are
supposed to account only paging events involving IO while currently they
include faulting in zero pages and zapping a process address space.
Probably, this should be revised before rolling out to cgroup v2.