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    SubjectRe: frequent lockups in 3.18rc4
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    On Fri, Dec 5, 2014 at 11:04 AM, Chris Mason <clm@fb.com> wrote:
    >
    > So one idea is that our allocation/freeing of pages is dramatically more
    > expensive and we're hitting a strange edge condition. Maybe we're even
    > faulting on a readonly page from a horrible place?

    Well, various allocators have definitely shown up a lot.
    DEBUG_PAGEALLOC does horrible things to performance, though, and the
    kernel will just spend a *lot* of time in memory allocators when it is
    on. So it might just be "yeah, the traces show allocations a lot, but
    that might just be because allocation is slow". The last one showed
    slub debugging - getting a call trace for the allocation.

    > [83246.925234] end_request: I/O error, dev sda, sector 0
    >
    > Ext3/4 shouldn't be doing IO to sector zero. Something is stomping on ram?

    I'd buy memory corruption through wild pointers as the reason, but
    quite frankly, that tends to have completely different failure modes.
    Not NMI watchdogs.

    So it must be some very particular corruption. I still vote for "let's
    see if Dave can narrow it down with bisection".

    Linus


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