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SubjectRe: [patch -mm 4/9 v2] oom: remove compulsory panic_on_oom mode
On Wed, 17 Feb 2010, KAMEZAWA Hiroyuki wrote:

> > We want to lock all populated zones with ZONE_OOM_LOCKED to avoid
> > needlessly killing more than one task regardless of how many memcgs are
> > oom.
> >
> Current implentation archive what memcg want. Why remove and destroy memcg ?
>

I've updated my patch to not take ZONE_OOM_LOCKED for any zones on memcg
oom. I'm hoping that you will add sysctl_panic_on_oom == 2 for this case
later, however.

> What I mean is
> - What VM_FAULT_OOM means is not "memory is exhausted" but "something is exhausted".
>
> For example, when hugepages are all used, it may return VM_FAULT_OOM.
> Especially when nr_overcommit_hugepage == usage_of_hugepage, it returns VM_FAULT_OOM.
>

The hugetlb case seems to be the only misuse of VM_FAULT_OOM where it
doesn't mean we simply don't have the memory to handle the page fault,
i.e. your earlier "memory is exhausted" definition. That was handled well
before calling out_of_memory() by simply killing current since we know it
is faulting hugetlb pages and its resource is limited.

We could pass the vma to pagefault_out_of_memory() and simply kill current
if its killable and is_vm_hugetlb_page(vma).


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