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    SubjectRe: [PATCH v6 6/7] sched: add SD_BALANCE_NEWIDLE at MC and CPU level for sched_mc>0
    On Wed, 17 Dec 2008 22:57:38 +0530
    Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> wrote:

    > --- a/include/linux/sched.h
    > +++ b/include/linux/sched.h
    > @@ -782,6 +782,16 @@ enum powersavings_balance_level {
    > ((sched_mc_power_savings || sched_smt_power_savings) ? \
    > SD_POWERSAVINGS_BALANCE : 0)

    What's with all the crappy macros in here?

    > +/*
    > + * Optimise SD flags for power savings:
    > + * SD_BALANCE_NEWIDLE helps agressive task consolidation and power savings.
    > + * Keep default SD flags if sched_{smt,mc}_power_saving=0
    > + */
    > +
    > +#define POWERSAVING_SD_FLAGS \
    > + ((sched_mc_power_savings || sched_smt_power_savings) ? \
    > + SD_BALANCE_NEWIDLE : 0)

    This one purports to be a constant, but it isn't - it's code.

    It would be cleaner, clearer and more idiomatic to do

    static inline int powersaving_sd_flags(void)
    {
    ...
    }

    Also, doing (sched_mc_power_savings | sched_smt_power_saving) might
    save a branch.

    > #define test_sd_parent(sd, flag) ((sd->parent && \
    > (sd->parent->flags & flag)) ? 1 : 0)

    buggy when passed an expression with side-effects. Doesn't need to be
    implemented as a macro.


    Sigh.




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