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SubjectRe: [PATCH tip/core/timers 2/4] timers: Reduce __run_timers() latency for empty list
On Wed, Jan 15, 2014 at 03:47:10PM -0500, Steven Rostedt wrote:
> On Wed, 15 Jan 2014 12:32:45 -0800
> Josh Triplett <josh@joshtriplett.org> wrote:
>
> > On Wed, Jan 15, 2014 at 06:38:58PM +0100, Oleg Nesterov wrote:
> > > forgot to mention...
> > >
> > > On 01/14, Paul E. McKenney wrote:
> > > >
> > > > +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;
> > > > +}
> > >
> > > Do we really want ifdef?
> > >
> > > This check is cheap, and !CONFIG_NO_HZ_FULL case looks a bit
> > > strange because we still update ->all_timers for no reason.
> >
> > There's an easy way to improve this: instead of using an ifdef, put
> > "IS_ENABLED(CONFIG_NO_HZ_FULL) && " in the if condition.
>
> Why even bother with that? What's wrong with doing this check all the
> time? Looks like it will save of the normal case too.

Sold! I removed the ifdef.

Thanx, Paul



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