linux-kernel - Re: [PATCH v5 3/3] mm,page_owner: Filter out stacks by a threshold counter

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Date:   Mon, 22 May 2023 10:40:55 +0200
From:   Alexander Potapenko <glider@...gle.com>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Waiman Long <longman@...hat.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Marco Elver <elver@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH v5 3/3] mm,page_owner: Filter out stacks by a threshold counter

On Tue, May 16, 2023 at 8:25 PM Oscar Salvador <osalvador@...e.de> wrote:
>
> We want to be able to filter out the output on a threshold basis,
> in this way we can get rid of a lot of noise and focus only on those
> stacks which have an allegedly high counter.
>
> We can control the threshold value by a new file called
> 'page_owner_threshold', which is 0 by default.
>
> Signed-off-by: Oscar Salvador <osalvador@...e.de>

Nack.
We must decouple stackdepot from page_owner as much as possible, not
add extra dependencies by sharing variables between the two.

What you need here is a pair of xxx_iter_start()/xxx_iter_next()
functions in stackdepot.c that will hold the iteration state in a
struct and return the next stack trace.
The threshold value can also be part of that struct.