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    SubjectRe: [PATCH 1/5] mm: Add __GFP_NO_OOM_KILL flag
    On Thursday 07 May 2009, David Rientjes wrote:
    > On Thu, 7 May 2009, Rafael J. Wysocki wrote:
    > > OK, let's try with __GFP_NO_OOM_KILL first. If there's too much disagreement,
    > > I'll use the freezer-based approach instead.
    > >
    > Third time I'm going to suggest this, and I'd like a response on why it's
    > not possible instead of being ignored.
    > All of your tasks are in D state other than kthreads, right? That means
    > they won't be in the oom killer (thus no zones are oom locked), so you can
    > easily do this
    > struct zone *z;
    > for_each_populated_zone(z)
    > zone_set_flag(z, ZONE_OOM_LOCKED);
    > and then
    > for_each_populated_zone(z)
    > zone_clear_flag(z, ZONE_OOM_LOCKED);
    > The serialization is done with trylocks so this will never invoke the oom
    > killer because all zones in the allocator's zonelist will be oom locked.

    Well, that might have been a good idea if it actually had worked. :-(

    > Why does this not work for you?

    If I set image_size to something below "hard core working set" +
    totalreserve_pages, preallocate_image_memory() hangs the
    box (please refer to the last patch I sent,

    However, with the freezer-based disabling of the OOM killer it doesn't hang
    under the same test conditions.

    The difference appears to be that using your approach makes
    __alloc_pages_internal() loop forever between the !try_set_zone_oom() test and
    restart:, while it should go to nopage: in that situation.

    So, I think I'll stick to the Andrew's approach with using __GFP_NO_OOM_KILL.


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