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    SubjectRe: [PATCH] [31/31] HWPOISON: Add a madvise() injector for soft page offlining
    On Sat, Jun 19, 2010 at 03:25:16PM +0200, Michael Kerrisk wrote:
    > Hi Andi,
    >
    > Thanks for this. Some comments below.
    >
    > On Sat, Jun 19, 2010 at 3:20 PM, Andi Kleen <andi@firstfloor.org> wrote:
    > > On Sat, Jun 19, 2010 at 02:36:28PM +0200, Michael Kerrisk wrote:
    > >> Hi Andi,
    > >>
    > >> On Tue, Dec 8, 2009 at 11:16 PM, Andi Kleen <andi@firstfloor.org> wrote:
    > >> >
    > >> > Process based injection is much easier to handle for test programs,
    > >> > who can first bring a page into a specific state and then test.
    > >> > So add a new MADV_SOFT_OFFLINE to soft offline a page, similar
    > >> > to the existing hard offline injector.
    > >>
    > >> I see that this made its way into 2.6.33. Could you write a short
    > >> piece on it for the madvise.2 man page?
    > >
    > > Also fixed the previous snippet slightly.
    >
    > (thanks)
    >
    > > commit edb43354f0ffc04bf4f23f01261f9ea9f43e0d3d
    > > Author: Andi Kleen <ak@linux.intel.com>
    > > Date:   Sat Jun 19 15:19:28 2010 +0200
    > >
    > >    MADV_SOFT_OFFLINE
    > >
    > >    Signed-off-by: Andi Kleen <ak@linux.intel.com>
    > >
    > > diff --git a/man2/madvise.2 b/man2/madvise.2
    > > index db29feb..9dccd97 100644
    > > --- a/man2/madvise.2
    > > +++ b/man2/madvise.2
    > > @@ -154,7 +154,15 @@ processes.
    > >  This operation may result in the calling process receiving a
    > >  .B SIGBUS
    > >  and the page being unmapped.
    > > -This feature is intended for memory testing.
    > > +This feature is intended for testing of memory error handling code.
    > > +This feature is only available if the kernel was configured with
    > > +.BR CONFIG_MEMORY_FAILURE .
    > > +.TP
    > > +.BR MADV_SOFT_OFFLINE " (Since Linux 2.6.33)
    > > +Soft offline a page. This will result in the memory of the page
    > > +being copied to a new page and original page be offlined. The operation
    >
    > Can you explain the term "offlined" please.

    The memory is not used anymore and taken out of normal
    memory management (until unpoisoned)
    and the "HardwareCorrupted:" counter in /proc/meminfo increases

    (don't put the later in, I'm thinking about changing that)

    >
    > > +should be transparent to the calling process.
    >
    > Does "should be transparent" mean "is normally invisible"?

    Yes. It's similar to being swapped out and swapped in again.

    -Andi
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