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    SubjectRe: [PATCH 7/7] xfs: Don't use PF_MEMALLOC
    Date
    > On Tue, Nov 17, 2009 at 04:23:43PM +0900, KOSAKI Motohiro wrote:
    > >
    > > Non MM subsystem must not use PF_MEMALLOC. Memory reclaim need few
    > > memory, anyone must not prevent it. Otherwise the system cause
    > > mysterious hang-up and/or OOM Killer invokation.
    >
    > The xfsbufd is a woken run by a registered memory shaker. i.e. it
    > runs when the system needs to reclaim memory. It forceѕ the
    > delayed write metadata buffers (of which there can be a lot) to disk
    > so that they can be reclaimed on IO completion. This IO submission
    > may require ѕome memory to be allocated to be able to free that
    > memory.
    >
    > Hence, AFAICT the use of PF_MEMALLOC is valid here.

    Thanks a lot.
    I have one additional question, may I ask you?

    How can we calculate maximum memory usage in xfsbufd?
    I'm afraid that VM and XFS works properly but adding two makes memory exhaust.

    And, I conclude XFS doesn't need sharing reservation memory with VM,
    it only need non failed allocation. right? IOW I'm prefer perter's
    suggestion.


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