On Fri, 23 Apr 2010, Nick Piggin wrote:
> > The oom killer rewrite attempts to kill current first, if possible, and
> > then will panic if panic_on_oom is set before falling back to selecting a
> > victim.
>
> See, this is what we want to avoid. If the user sets panic_on_oom,
> it is because they want the system to panic on oom. Not to kill
> tasks and try to continue. The user does not know or care in the
> slightest about "page fault oom". So I don't know why you think this
> is a good idea.
>
Unless we unify the behavior of panic_on_oom, it would be possible for the
architectures that are not converted to using pagefault_out_of_memory()
yet using your patch series to kill tasks even if they have OOM_DISABLE
set. So, as it sits this second in -mm, the system will still try to kill
current first so that all architectures are consistent. Once all
architectures use pagefault_out_of_memory(), we can simply add
if (sysctl_panic_on_oom) {
read_lock(&tasklist_lock);
dump_header(NULL, 0, 0, NULL);
read_unlock(&tasklist_lock);
panic("Out of memory: panic_on_oom is enabled\n");
}
to pagefault_out_of_memory(). I simply opted for consistency across all
architectures before that was done.
> > This is consistent with all other architectures such as powerpc
> > that currently do not use pagefault_out_of_memory(). If all architectures
> > are eventually going to be converted to using pagefault_out_of_memory()
>
> Yes, architectures are going to be converted, it has already been
> agreed, I dropped the ball and lazily hoped the arch people would do it.
> But further work done should be to make it consistent in the right way,
> not the wrong way.
>
Thanks for doing the work and proposing the patchset, there were a couple
of patches that looked like it needed a v2, but overall it looked very
good. Once they're merged in upstream, I think we can add the panic to
pagefault_out_of_memory() in -mm since they'll probably make it to Linus
before the oom killer rewrite at the speed we're going here.
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