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Date:   Tue, 29 Jan 2019 17:15:49 -0500
From:   Johannes Weiner <hannes@cmpxchg.org>
To:     Chris Down <chris@chrisdown.name>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Tejun Heo <tj@kernel.org>, Roman Gushchin <guro@fb.com>,
        linux-kernel@vger.kernel.org, cgroups@vger.kernel.org,
        linux-mm@kvack.org, kernel-team@fb.com
Subject: Re: [PATCH] mm: memcontrol: Expose THP events on a per-memcg basis
Message-ID: <20190129221549.GA13066@cmpxchg.org>
References: <20190129205852.GA7310@chrisdown.name>
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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@chrisdown.name>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Roman Gushchin <guro@fb.com>
> Cc: linux-kernel@vger.kernel.org
> Cc: cgroups@vger.kernel.org
> Cc: linux-mm@kvack.org
> Cc: kernel-team@fb.com

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@cmpxchg.org>

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.