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SubjectRe: [patch -mm 4/9 v2] oom: remove compulsory panic_on_oom mode
On Tue, 16 Feb 2010, Nick Piggin wrote:

> What is the point of removing it, though? If it doesn't significantly
> help some future patch, just leave it in. It's not worth breaking the
> user/kernel interface just to remove 3 trivial lines of code.
>

Because it is inconsistent at the user's expense, it has never panicked
the machine for memory controller ooms, so why is a cpuset or mempolicy
constrained oom conditions any different? It also panics the machine even
on VM_FAULT_OOM which is ridiculous, the tunable is certainly not being
used how it was documented and so given the fact that mempolicy
constrained ooms are now much smarter with my rewrite and we never simply
kill current unless oom_kill_quick is enabled anymore, the compulsory
panic_on_oom == 2 mode is no longer required. Simply set all tasks
attached to a cpuset or bound to a specific mempolicy to be OOM_DISABLE,
the kernel need not provide confusing alternative modes to sysctls for
this behavior. Before panic_on_oom == 2 was introduced, it would have
only panicked the machine if panic_on_oom was set to a non-zero integer,
defining it be something different for '2' after it has held the same
semantics for years is inappropriate. There is just no concrete example
that anyone can give where they want a cpuset-constrained oom to panic the
machine when other tasks on a disjoint set of mems can continue to do
work and the cpuset of interest cannot have its tasks set to OOM_DISABLE.


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