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    SubjectRe: [patch] tracing/mm: add page frame snapshot trace

    * Wu Fengguang <fengguang.wu@intel.com> wrote:

    > Hi Ingo,
    >
    > On Sat, May 09, 2009 at 02:27:58PM +0800, Ingo Molnar wrote:
    > >
    > > * Wu Fengguang <fengguang.wu@intel.com> wrote:
    > >
    > > > > So this should be done in cooperation with instrumentation
    > > > > folks, while improving _all_ of Linux instrumentation in
    > > > > general. Or, if you dont have the time/interest to work with us
    > > > > on that, it should not be done at all. Not having the
    > > > > resources/interest to do something properly is not a license to
    > > > > introduce further instrumentation crap into Linux.
    > > >
    > > > I'd be glad to work with you on the 'object collections' ftrace
    > > > interfaces. Maybe next month. For now my time have been allocated
    > > > for the hwpoison work, sorry!
    > >
    > > No problem - our offer still stands: we are glad to help out with
    > > the instrumentation side bits. We'll even write all the patches for
    > > you, just please help us out with making it maximally useful to
    > > _you_ :-)
    >
    > Thank you very much!
    >
    > The good fact is, 2/3 of the code and experiences can be reused.
    >
    > > Find below a first prototype patch written by Steve yesterday and
    > > tidied up a bit by me today. It can also be tried on latest -tip:
    > >
    > > http://people.redhat.com/mingo/tip.git/README
    > >
    > > This patch adds the first version of the 'object collections'
    > > instrumentation facility under /debug/tracing/objects/mm/. It has a
    > > single control so far, a 'number of pages to dump' trigger file:
    > >
    > > To dump 1000 pages to the trace buffers, do:
    > >
    > > echo 1000 > /debug/tracing/objects/mm/pages/trigger
    > >
    > > To dump all pages to the trace buffers, do:
    > >
    > > echo -1 > /debug/tracing/objects/mm/pages/trigger
    >
    > That is not too intuitive, I'm afraid.

    This was just a first-level approximation - and it matches the usual
    "0xffffffff means infinite" idiom.

    How about changing it from 'trigger' to 'dump_range':

    echo "*" > /debug/tracing/objects/mm/pages/dump_range

    being a shortcut for 'dump all'?

    And:

    echo "1000 2000" > /debug/tracing/objects/mm/pages/dump_range

    ?

    The '1000' is the offset where the dumping starts, and 2000 is the
    size of the dump.

    Ingo


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