On Thu 28-01-21 13:28:10, Cristopher Lameter wrote:

On Thu, 28 Jan 2021, Michal Hocko wrote:

quoted

quoted

So, if I understand your concerns correct this implementation has two
issues:
1) allocation failure at page fault that causes unrecoverable OOM and
2) a possibility for an unprivileged user to deplete secretmem pool and
cause (1) to others

I'm not really familiar with OOM internals, but when I simulated an
allocation failure in my testing only the allocating process and it's
parent were OOM-killed and then the system continued normally.

If you kill the allocating process then yes, it would work, but your
process might be the very last to be selected.

OOMs are different if you have a "constrained allocation". In that case it
is the fault of the process who wanted memory with certain conditions.
That memory is not available. General memory is available though. In that
case the allocating process is killed.

I do not see this implementation would do anything like that. Neither
anything like that implemented in the oom killer. Constrained
allocations (cpusets/memcg/mempolicy) only do restrict their selection
to processes which belong to the same domain. So I am not really sure
what you are referring to. The is only a global knob to _always_ kill
the allocating process on OOM.

-- 
Michal Hocko
SUSE Labs

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