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

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Message-ID: <ZdTSAWwNng9rmKtg@tiehlicka>
Date: Tue, 20 Feb 2024 17:23:29 +0100
From: Michal Hocko <mhocko@...e.com>
To: Suren Baghdasaryan <surenb@...gle.com>
Cc: Kent Overstreet <kent.overstreet@...ux.dev>,
	Steven Rostedt <rostedt@...dmis.org>,
	Vlastimil Babka <vbabka@...e.cz>, akpm@...ux-foundation.org,
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Subject: Re: [PATCH v3 31/35] lib: add memory allocations report in show_mem()

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 Hocko
SUSE Labs