Re: [PATCH v3 31/35] lib: add memory allocations report in show_mem()

On Tue 20-02-24 12:18:49, Kent Overstreet wrote:

On Tue, Feb 20, 2024 at 05:23:29PM +0100, Michal Hocko wrote:

quoted

On Mon 19-02-24 09:17:36, Suren Baghdasaryan wrote:
[...]

quoted

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.

Your argument makes little sense and it seems that it is impossible to
explain that to you. I gave up on discussing this further with you.

Consider NAK to any additional allocation from oom path unless you can
give very _solid_ arguments this is absolutely necessary. "It's gona be
fine and work most of the time" is not a solid argument.
-- 
Michal Hocko
SUSE Labs