Re: [PATCH] mm: memcontrol: Expose THP events on a per-memcg basis

[Johannes Weiner]

On Tue, Jan 29, 2019 at 03:58:52PM -0500, Chris Down wrote:
> Currently THP allocation events data is fairly opaque, since you can
> only get it system-wide. This patch makes it easier to reason about
> transparent hugepage behaviour on a per-memcg basis.
> 
> For anonymous THP-backed pages, we already have MEMCG_RSS_HUGE in v1,
> which is used for v1's rss_huge [sic]. This is reused here as it's
> fairly involved to untangle NR_ANON_THPS right now to make it
> per-memcg, since right now some of this is delegated to rmap before we
> have any memcg actually assigned to the page. It's a good idea to rework
> that, but let's leave untangling THP allocation for a future patch.
>
> Signed-off-by: Chris Down <chris@xxxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Tejun Heo <tj@xxxxxxxxxx>
> Cc: Roman Gushchin <guro@xxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: cgroups@xxxxxxxxxxxxxxx
> Cc: linux-mm@xxxxxxxxx
> Cc: kernel-team@xxxxxx

Looks good to me. It's useful to know if a cgroup is getting the THP
coverage and allocation policy it's asking for.

Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>

The fallback numbers could be useful as well, but they're tricky to
obtain as there isn't an obvious memcg context. We can do them later.