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    SubjectRe: [PATCH v6 6/7] sched: add SD_BALANCE_NEWIDLE at MC and CPU level for sched_mc>0
    * Ingo Molnar <mingo@elte.hu> [2008-12-18 13:46:44]:

    >
    > * Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> wrote:
    >
    > > * Andrew Morton <akpm@linux-foundation.org> [2008-12-17 17:42:54]:
    > >
    > > > 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?
    > >
    > > Hi Andrew,
    > >
    > > These macros set the SD_POWERSAVINGS_BALANCE flag based on the
    > > sysfs tunable.
    > >
    > > > > +/*
    > > > > + * 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)
    > > > {
    > > > ...
    > > > }
    > >
    > > Your are suggesting to move these to inline functions. I will write
    > > a patch and post for review.
    > >
    > > > 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.
    > >
    > > Agreed, but these macros are used throughout sched.c and are performance
    > > sensitive. Inline functions are a close enough replacement for the
    > > macro let me look for any performance penalty as well and report.
    >
    > those macros are historic so feel free to convert them to inlines without
    > re-measuring performance impact.

    Sure Ingo. I will go ahead and change them in my next iteration.

    > The patchset looks pretty good in principle otherwise, so if you could
    > address Andrew's comments and clean up those bits in the next iteration we
    > could start testing it in the scheduler tree. (Please also add Balbir
    > Singh's acks to the next iteration.)

    Thank you for acking the patch. I will address Andrew's comments and
    post the next iteration along with Balbir's acks.

    > and please fix your mailer to not inject stuff like this:
    >
    > Mail-Followup-To: Andrew Morton <akpm@linux-foundation.org>,
    > linux-kernel@vger.kernel.org, suresh.b.siddha@intel.com,
    > venkatesh.pallipadi@intel.com, a.p.zijlstra@chello.nl,
    > mingo@elte.hu, dipankar@in.ibm.com, balbir@linux.vnet.ibm.com,
    > vatsa@linux.vnet.ibm.com, ego@in.ibm.com, andi@firstfloor.org,
    > davecb@sun.com, tconnors@astro.swin.edu.au, maxk@qualcomm.com,
    > gregory.haskins@gmail.com, pavel@suse.cz
    >
    > It utterly messed up the addressing mode of my reply here and i had to
    > edit the raw email headers manually to fix it up ;-)

    OOPS! My bad mutt config! I have tried to fix this. Hopefully this
    will not cause trouble anymore.

    Thanks,
    Vaidy


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