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    SubjectRe: [PATCH] Remove OOM killer from try_to_free_pages / all_unreclaimable braindamage


    Andrea Arcangeli wrote:

    >On Fri, Nov 05, 2004 at 03:32:50PM -0800, Jesse Barnes wrote:
    >
    >>On Friday, November 05, 2004 12:01 pm, Marcelo Tosatti wrote:
    >>
    >>>In my opinion the correct approach is to trigger the OOM killer
    >>>when kswapd is unable to free pages. Once that is done, the number
    >>>of tasks inside page reclaim is irrelevant.
    >>>
    >>That makes sense.
    >>
    >
    >I don't like it, kswapd may fail balancing because there's a GFP_DMA
    >allocation that eat the last dma page, but we should not kill tasks if
    >we fail to balance in kswapd, we should kill tasks only when no fail
    >path exists (i.e. only during page faults, everything else in the kernel
    >has a fail path and it should never trigger oom).
    >
    >If you move it in kswapd there's no way to prevent oom-killing from a
    >syscall allocation (I guess even right now it would go wrong in this
    >sense, but at least right now it's more fixable). I want to move the oom
    >kill outside the alloc_page paths. The oom killing is all about the page
    >faults not having a fail path, and in turn the oom killing should be
    >moved in the page fault code, not in the allocator. Everything else
    >should keep returning -ENOMEM to the caller.
    >
    >

    Probably a good idea. OTOH, some kernel allocations might really
    need to be performed and have no failure path. For example __GFP_REPEAT.

    I think maybe __GFP_REPEAT allocations at least should be able to
    cause an OOM. Not sure though.

    >So to me moving the oom killer into kswapd looks a regression.
    >
    >
    >

    Also, I think it would do the wrong thing on NUMA machines because
    that has a per-node kswapd.

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