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    SubjectRe: Plumbers: Tweaking scheduler policy micro-conf RFP
    * Peter Zijlstra <peterz@infradead.org> [2012-05-15 17:35:41]:

    > On Tue, 2012-05-15 at 17:05 +0200, Vincent Guittot wrote:
    > > On 15 May 2012 15:00, Peter Zijlstra <peterz@infradead.org> wrote:
    > > > On Tue, 2012-05-15 at 14:57 +0200, Vincent Guittot wrote:

    [snip]

    > But really short, look at kernel/sched/core.c:default_topology[]
    >
    > I'd like to get rid of sd_init_* into a single function like
    > sd_numa_init(), this would mean all archs would need to do is provide a
    > simple list of ever increasing masks that match their topology.

    You are suggesting that the archs will provide sched/core a list of
    masks equivalent to the number of sched domain levels that we need to
    build. The SDTL_SHARE_XXX flag will also be passed per mask in order
    to decide the SD flags for that domain.

    > To aid this we can add some SDTL_flags, initially I was thinking of:
    >
    > SDTL_SHARE_CORE -- aka SMT
    > SDTL_SHARE_CACHE -- LLC cache domain (typically multi-core)
    > SDTL_SHARE_MEMORY -- NUMA-node (typically socket)
    >
    > The 'performance' policy is typically to spread over shared resources so
    > as to minimize contention on these.
    >
    > If you want to add some power we need some extra flags, maybe something
    > like:
    >
    > SDTL_SHARE_POWERLINE -- power domain (typically socket)

    Let me take a case of two-socket,quad-core,HT x86 (Nehalem):

    SDTL_SHARE_POWERLINE should be passed along with a cpumask that
    represents sd_init_CPU or cpu_cpu_mask today. So the number of
    domains we build per-cpu will depend on the topology and the
    sched_powersavings settings.

    --Vaidy



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