linux-kernel - Re: [PATCH v3 31/35] lib: add memory allocations report in show

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Date: Tue, 20 Feb 2024 12:18:49 -0500
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Michal Hocko <mhocko@...e.com>
Cc: Suren Baghdasaryan <surenb@...gle.com>, 
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Subject: Re: [PATCH v3 31/35] lib: add memory allocations report in show_mem()

On Tue, Feb 20, 2024 at 05:23:29PM +0100, Michal Hocko wrote:
> On Mon 19-02-24 09:17:36, Suren Baghdasaryan wrote:
> [...]
> > For now I think with Vlastimil's __GFP_NOWARN suggestion the code
> > becomes safe and the only risk is to lose this report. If we get cases
> > with reports missing this data, we can easily change to reserved
> > memory.
> 
> This is not just about missing part of the oom report. This is annoying
> but not earth shattering. Eating into very small reserves (that might be
> the only usable memory while the system is struggling in OOM situation)
> could cause functional problems that would be non trivial to test for.
> All that for debugging purposes is just lame. If you want to reuse the code
> for a different purpose then abstract it and allocate the buffer when you
> can afford that and use preallocated on when in OOM situation.
> 
> We have always went extra mile to avoid potentially disruptive
> operations from the oom handling code and I do not see any good reason
> to diverge from that principle.

Michal, I gave you the logic between dedicated reserves and system
reserves. Please stop repeating these vague what-ifs.