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    SubjectRe: [PATCH 15/15] x86: Fix cpu_coregroup_mask to return correct cpumask on multi-node processors
    On Tue, Aug 25, 2009 at 12:35:02PM +0200, Peter Zijlstra wrote:
    > On Tue, 2009-08-25 at 12:24 +0200, Andreas Herrmann wrote:
    > > On Tue, Aug 25, 2009 at 11:55:43AM +0200, Peter Zijlstra wrote:
    > > > On Tue, 2009-08-25 at 11:31 +0200, Andreas Herrmann wrote:
    > > > > On Mon, Aug 24, 2009 at 05:36:16PM +0200, Peter Zijlstra wrote:
    > > > > > On Thu, 2009-08-20 at 15:46 +0200, Andreas Herrmann wrote:
    > > > > > > The correct mask that describes core-siblings of an processor
    > > > > > > is topology_core_cpumask. See topology adapation patches, especially
    > > > > > > http://marc.info/?l=linux-kernel&m=124964999608179
    > > > > >
    > > > > >
    > > > > > argh, violence, murder kill.. this is the worst possible hack and you're
    > > > > > extending it :/
    > > > >
    > > > > So this is the third code area
    > > > > (besides sched_*_power_savings sysfs interface, and the __cpu_power fiddling)
    > > > > that is crap, mess, a hack.
    > > > >
    > > > > Didn't know that I'd enter such a minefield when touching this code. ;-(
    > > >
    > > > Yeah, you're lucky that way ;-) Its been creaking for a while, and I've
    > > > been making noises to the IBM people (who so far have been the main
    > > > source of power saving patches) to clean this up, but now you trod onto
    > > > all of it at once..
    > > >
    > > > > What would be your perferred solution for the
    > > > > core_cpumask/llc_shared_map stuff? Another domain level to get rid of
    > > > > this function?
    > > >
    > > > Right, I'd like to see everything exposed as domain levels.
    > > >
    > > >
    > > > numa-cluster
    > > > numa
    > > > socket
    > > > in-socket-numa
    > > > multi-core
    > > > shared-cache
    > > > core
    > > > threads
    > > >
    > > > We currently have a fixed order of these things, but I think we should
    > > > simply provide helpers for building the sd tree and let the arch code do
    > > > that instead of exporting all these masks in a fixed order.
    > > >
    > > > Once we get the arch domain tree, we do degenerate stuff to cull all the
    > > > trivial domains and fold SD flags.
    > >
    > > So any in-socket-numa is only going to haeppen with the arch-defined
    > > domain tree.
    >
    > Well, we could see what it takes to make this work without that. I mean,
    > this is just how I'd like to see it end up, doesn't mean we cannot work
    > on it from multiple angles at the same time.

    Yup.

    > > Now that this is settled you should throw away the
    > > __build_sched_domains cleanup patches that are in tip. They won't be
    > > of use when domain creation code is basically changed.
    >
    > I'm not sure that's needed, we can continue work on refactoring that.
    > Small steps towards something better seems a better plan than a single
    > large step.

    Ok.


    Andreas

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