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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 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.

    - Josh Triplett


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