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    SubjectRe: [PATCH 02/10] mm: system wide ALLOC_NO_WATERMARK
    On Mon, Aug 06, 2007 at 11:51:45AM -0700, Christoph Lameter wrote:
    > On Mon, 6 Aug 2007, Daniel Phillips wrote:
    >
    > > On Monday 06 August 2007 11:42, Christoph Lameter wrote:
    > > > On Mon, 6 Aug 2007, Daniel Phillips wrote:
    > > > > Currently your system likely would have died here, so ending up
    > > > > with a reserve page temporarily on the wrong node is already an
    > > > > improvement.
    > > >
    > > > The system would have died? Why?
    > >
    > > Because a block device may have deadlocked here, leaving the system
    > > unable to clean dirty memory, or unable to load executables over the
    > > network for example.
    >
    > So this is a locking problem that has not been taken care of?

    No.

    It's very simple:

    1) memory becomes full
    2) we try to free memory by paging or swapping
    3) I/O requires a memory allocation which fails because memory is full
    4) box dies because it's unable to dig itself out of OOM

    Most I/O paths can deal with this by having a mempool for their I/O
    needs. For network I/O, this turns out to be prohibitively hard due to
    the complexity of the stack.

    --
    Mathematics is the supreme nostalgia of our time.
    -
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