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SubjectRe: [PATCH 2/4] mm: memcontrol: re-use global VM event enum
On Fri, Apr 07, 2017 at 02:47:02PM +0200, Michal Hocko wrote:
> I do agree that we should share global and memcg specific events constants
> but I am not sure we want to share all of them. Would it make sense to
> reorganize the global enum and put those that are shared to the
> beginning? We wouldn't need the memcg specific translation then.

I'm not sure I follow. Which translation?

> Anyway, two comments on the current implementation.
>
> On Tue 04-04-17 18:01:46, Johannes Weiner wrote:
> [...]
> > +/* Cgroup-specific events, on top of universal VM events */
> > +enum memcg_event_item {
> > + MEMCG_LOW = NR_VM_EVENT_ITEMS,
> > + MEMCG_HIGH,
> > + MEMCG_MAX,
> > + MEMCG_OOM,
> > + MEMCG_NR_EVENTS,
> > +};
>
> The above should mention that each supported global VM event should
> provide the corresponding translation
>
> [...]
>
> here...
> > +/* Universal VM events cgroup1 shows, original sort order */
> > +unsigned int memcg1_events[] = {
> > + PGPGIN,
> > + PGPGOUT,
> > + PGFAULT,
> > + PGMAJFAULT,
> > +};
> > +
> > +static const char *const memcg1_event_names[] = {
> > + "pgpgin",
> > + "pgpgout",
> > + "pgfault",
> > + "pgmajfault",
> > +};
>
> the naming doesn't make it easier to undestand why we need this.
> global2memcg_event?

This is just to keep the file order consistent. It could have been
done like memory.stat in cgroup2, where we simply do

seq_printf(s, "pgmajfault %lu\n", stat[PGMAJFAULT]);

but I didn't want to change the v1 code too much. So these two arrays
are just a sorted list of global VM events shown in v1's memory.stat.

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