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Date:   Wed, 18 Oct 2023 12:27:36 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Yosry Ahmed <yosryahmed@google.com>
Cc:     Michal =?UTF-8?B?S291dG7DvQ==?= <mkoutny@suse.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Shakeel Butt <shakeelb@google.com>,
        Michal Hocko <mhocko@kernel.org>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Muchun Song <muchun.song@linux.dev>, linux-mm@kvack.org,
        cgroups@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/2] mm: memcg: refactor page state unit helpers
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On Thu, 5 Oct 2023 10:30:36 -0700 Yosry Ahmed <yosryahmed@google.com> wrote:

> On Thu, Oct 5, 2023 at 9:30 AM Michal Koutný <mkoutny@suse.com> wrote:
> >
> > On Thu, Oct 05, 2023 at 02:31:03AM -0700, Yosry Ahmed <yosryahmed@google.com> wrote:
> > > I am not really sure what you mean here.
> >
> > My "vision" is to treat WORKINGSET_ entries as events.
> > That would mean implementing per-node tracking for vm_event_item
> > (costlier?).
> > That would mean node_stat_item and vm_event_item being effectively
> > equal, so they could be merged in one.
> > That would be situation to come up with new classification based on use
> > cases (e.g. precision/timeliness requirements, state vs change
> > semantics).
> >
> > (Do not take this as blocker of the patch 1/2, I rather used the
> > opportunity to discuss a greater possible cleanup.)
> 
> Yeah ideally we can clean this up separately. I would be careful about
> userspace exposure though. It seems like CONFIG_VM_EVENT_COUNTERS is
> used to control tracking events and displaying them in vmstat, so
> moving items between node_stat_item and vm_event_item (or merging
> them) won't be easy.

I like the word "separately".  This series has been in mm-unstable for
nearly a month, so I'll move it into mm-stable as-is,