linux-kernel - Re: [PATCH] mm/page_owner: print largest memory consumer when OOM panic occurs

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Message-Id: <2EA70B54-A7E1-4C5A-A447-844A3FEA7E93@lca.pw>
Date:   Fri, 27 Dec 2019 08:46:03 -0500
From:   Qian Cai <cai@....pw>
To:     Miles Chen <miles.chen@...iatek.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-mediatek@...ts.infradead.org,
        wsd_upstream@...iatek.com
Subject: Re: [PATCH] mm/page_owner: print largest memory consumer when OOM panic occurs

> On Dec 27, 2019, at 2:44 AM, Miles Chen <miles.chen@...iatek.com> wrote:
> 
> It's not complete situation.
> 
> I've listed different OOM panic situations in previous email [1]
> and what we can do about them with current information.
> 
> There are some cases which cannot be covered by current information
> easily.
> For example: a memory leakage caused by alloc_pages() or vmalloc() with
> a large size.
> I keep seeing these issues for years and that's why I built this patch. 
> It's like a missing piece of the puzzle.
> 
> To prove that the approach is practical and useful, I have collected
> real test cases
> under real devices and posted the test result in the commit message.
> These are real cases, not my imagination.

Of course this may help debug *your* problems in the past, but if that is the only requirement to merge the debugging patch like this, we would end up with endless of those. If your goal is to stop developers from reproducing issues unnecessarily again using page_owner to debug, then your patch does not help much for the majority of other developers’ issues.

The page_owner is designed to give information about the top candidates that might cause issues, so it make somewhat sense if it dumps the top 10 greatest memory consumer for example, but that also clutter the OOM report so much, so it is no-go.