lkml.org 
[lkml]   [2008]   [Dec]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v6 6/7] sched: add SD_BALANCE_NEWIDLE at MC and CPU level for sched_mc>0
* 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.

Thanks for the review and comments.

--Vaidy


\
 
 \ /
  Last update: 2008-12-18 10:37    [W:0.419 / U:0.036 seconds]
©2003-2014 Jasper Spaans. Advertise on this site