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    SubjectRe: [Bug #13319] Page allocation failures with b43 and p54usb
    On Mon, 29 Jun 2009, Larry Finger wrote:

    > > Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=13319
    > > Subject : Page allocation failures with b43 and p54usb
    > > Submitter : Larry Finger <Larry.Finger@lwfinger.net>
    > > Date : 2009-04-29 21:01 (61 days old)
    > > References : http://marc.info/?l=linux-kernel&m=124103897101088&w=4
    > > http://lkml.org/lkml/2009/6/7/136
    > > Handled-By : Johannes Berg <johannes@sipsolutions.net>
    >
    > The cause of these failures has been determined. The wireless
    > subsystem frequently requests buffers of size 4096, but when SLUB
    > debugging is enabled and the debug info is added, the request becomes
    > of order 1 and memory becomes fragmented.
    >
    > A controversial "fix" in which SLUB debugging was disabled for
    > allocations where adding such debugging info would increase the order
    > was discussed and tried. With a quick look at the commit list for
    > Linus's tree, I don't see that such a patch is available, but I will
    > be corrected if I missed it.
    >

    I'd disagree with disabling slub debugging by default for caches where
    oo_order(s->min) increases as the result of using it. This particular
    page allocation failure is happening for, presumably, kmalloc-4096, and
    the system has 4K pages. Disabling debugging for that cache (and any of
    its aliases) implicitly will lead to errors going undiagnosed as a result.


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