Re: [PATCH tip/core/timers 2/4] timers: Reduce __run_timers() latency for empty list

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Wed, Jan 15, 2014 at 12:33:55PM -0800, Josh Triplett wrote:
> On Tue, Jan 14, 2014 at 09:20:46PM -0800, Paul E. McKenney wrote:
> > From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> > 
> > The __run_timers() function currently steps through the list one jiffy at
> > a time in order to update the timer wheel.  However, if the timer wheel
> > is empty, no adjustment is needed other than updating ->timer_jiffies.
> > In this case, which is likely to be common for NO_HZ_FULL kernels, the
> > kernel currently incurs a large latency for no good reason.  This commit
> > therefore short-circuits this case.
> > 
> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > ---
> >  kernel/timer.c | 15 +++++++++++++++
> >  1 file changed, 15 insertions(+)
> > 
> > diff --git a/kernel/timer.c b/kernel/timer.c
> > index 2245b7374c3d..295837e5e011 100644
> > --- a/kernel/timer.c
> > +++ b/kernel/timer.c
> > @@ -338,6 +338,17 @@ void set_timer_slack(struct timer_list *timer, int slack_hz)
> >  }
> >  EXPORT_SYMBOL_GPL(set_timer_slack);
> >  
> > +static bool catchup_timer_jiffies(struct tvec_base *base)
> > +{
> > +#ifdef CONFIG_NO_HZ_FULL
> > +	if (!base->all_timers) {
> > +		base->timer_jiffies = jiffies;
> > +		return 1;
> > +	}
> > +#endif /* #ifdef CONFIG_NO_HZ_FULL */
> > +	return 0;
> > +}
> 
> In a function with return type "bool", please use true/false, not 1/0.
> 
> Please also document the semantic of the return value.

Done for both, thank you.

							Thanx, Paul