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SubjectRe: [RFC][PATCH] memcg: page fault oom improvement v2
On Tue, 23 Feb 2010 17:42:33 -0800 (PST)
David Rientjes <rientjes@google.com> wrote:

> > >
> > > This allows us to hijack the TIF_MEMDIE bit to detect when there is a
> > > parallel pagefault oom killing when the oom killer hasn't necessarily been
> > > invoked to kill a system-wide task (it's simply killing current, by
> > > default, and giving it access to memory reserves). Then, we can change
> > > out_of_memory(), which also now handles memcg oom conditions, to always
> > > scan the tasklist first (including for mempolicy and cpuset constrained
> > > ooms), check for any candidates that have TIF_MEMDIE, and return
> > > ERR_PTR(-1UL) if so. That catches the parallel pagefault oom conditions
> > > from needlessly killing memcg tasks. panic_on_oom would only panic after
> > > the tasklist scan has completed and returned != ERR_PTR(-1UL), meaning
> > > pagefault ooms are exempt from that sysctl.
> > >
> > Sorry, I see your concern but I'd like not to do clean-up and bug-fix at
> > the same time.
> >
> > I think clean up after fix is easy in this case.
> >
>
> If you develop on top of my oom killer rewrite, pagefault ooms already
> attempt to kill current first and then defer back to killing another task
> if current is unkillable.

After my fix, page_fault_out_of_memory is never called. (because memcg doesn't
return needless failure.)

Then, that's not point in this thread.

Thanks,
-Kame



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