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    SubjectRe: [PATCH 1/5] mm: Add __GFP_NO_OOM_KILL flag
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    On Saturday 09 May 2009, David Rientjes wrote:
    > On Sat, 9 May 2009, Rafael J. Wysocki wrote:
    >
    > > > 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,
    > > http://patchwork.kernel.org/patch/22423/).
    > >
    >
    > This has been changed in the latest mmotm with Mel's page alloactor
    > patches (and I think yours should be based on mmotm). Specifically,
    > page-allocator-break-up-the-allocator-entry-point-into-fast-and-slow-paths.patch.
    >
    > Before his patchset, zonelists that had ZONE_OOM_LOCKED set for at least
    > one of their zones would unconditionally goto restart. Now, if
    > order > PAGE_ALLOC_COSTLY_ORDER, it gives up and returns NULL. Otherwise,
    > it does goto restart.
    >
    > So if your allocation has order > PAGE_ALLOC_COSTLY_ORDER,

    It doesn't. All of my allocations are of order 0.

    > using the ZONE_OOM_LOCKED approach to locking out the oom killer will work
    > just fine in mmotm.

    No, it won't, AFAICT.

    Best,
    Rafael


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