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    SubjectRe: [PATCH v4 0/2] Move x86_cpu_to_apicid to the __read_mostly section
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    On Monday, May 21, 2012 17:23:48 Ingo Molnar wrote:
    > * Vlad Zolotarov <vlad@scalemp.com> wrote:
    > > Pls., consider applying this patch series.
    > >
    > > It contains the following changes:
    > > - Adds two new macros DEFINE_EARLY_PER_CPU_READ_MOSTLY() and
    > >
    > > DECLARE_EARLY_PER_CPU_READ_MOSTLY().
    > >
    > > - Adds "read-mostly" qualifier to the following variables in smp.h:
    > > - cpu_sibling_map
    > > - cpu_core_map
    > > - cpu_llc_shared_map
    > > - cpu_llc_id
    > > - cpu_number
    > > - x86_cpu_to_apicid
    > > - x86_bios_cpu_apicid
    > > - x86_cpu_to_logical_apicid
    > >
    > > As long as all the variables above are only written during the
    > > initialization, this change is meant to prevent the false
    > > sharing and improve the performance on large multiprocessor
    > > systems.
    >
    > Why have you resent this? The feedback I gave has not been
    >
    > addressed:

    Hmmm... I'm a bit confused. There were two feedbacks/threads: one on "Signed-
    off-by" format and the other where u asked for a justification on a vSMP side.

    The signed-off format sounded to me as a clear blocker for a series so I fixed
    it and respined. I also mentioned it in patch0.

    The second thread seams like getting to submitting a separate patch with a doc
    under Documents and vSMP testing results explaining and justifying when and
    were per-CPU and/or __read_mostly variables should be used.

    Pls., correct me if I misunderstood u and let me know what should I do next in
    order to make this patch series accepted.

    thanks,
    vlad


    > > Well, a quick tally of percpu variables on a 'make defconfig'
    > > kernel would tell us one way or another?
    > >
    > > Here there's almost 200 percpu variables active in the 64-bit
    > > x86 defconfig, and a quick random sample suggests that most
    > > are read-mostly.
    > >
    > > I have no fundamental prefer to either approach, but the
    > > direction taken should be justified explicitly, with numbers,
    > > arguments, etc. - also a short blurb somewhere in the headers
    > > that explains when they should be used, so that others can be
    > > aware of vSMP's special needs here.
    >
    > Thanks,
    >
    > Ingo


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