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SubjectRe: [PATCH] time: tick-sched: use bool for tick_stopped
Hi Thomas,

On 2018-04-10 05:10 PM, Thomas Gleixner wrote:
> On Tue, 10 Apr 2018, yuankuiz@codeaurora.org wrote:
>> On 2018-04-10 04:00 PM, Rafael J. Wysocki wrote:
>> > On Tue, Apr 10, 2018 at 9:33 AM, <yuankuiz@codeaurora.org> wrote:
>> > > From: John Zhao <yuankuiz@codeaurora.org>
>> > >
>> > > Variable tick_stopped returned by tick_nohz_tick_stopped
>> > > can have only true / false values. Since the return type
>> > > of the tick_nohz_tick_stopped is also bool, variable
>> > > tick_stopped nice to have data type as bool in place of unsigned int.
>> > > Moreover, the executed instructions cost could be minimal
>> > > without potiential data type conversion.
>> > >
>> > > Signed-off-by: John Zhao <yuankuiz@codeaurora.org>
>> > > ---
>> > > kernel/time/tick-sched.h | 2 +-
>> > > 1 file changed, 1 insertion(+), 1 deletion(-)
>> > >
>> > > diff --git a/kernel/time/tick-sched.h b/kernel/time/tick-sched.h
>> > > index 6de959a..4d34309 100644
>> > > --- a/kernel/time/tick-sched.h
>> > > +++ b/kernel/time/tick-sched.h
>> > > @@ -48,8 +48,8 @@ struct tick_sched {
>> > > unsigned long check_clocks;
>> > > enum tick_nohz_mode nohz_mode;
>> > >
>> > > + bool tick_stopped : 1;
>> > > unsigned int inidle : 1;
>> > > - unsigned int tick_stopped : 1;
>> > > unsigned int idle_active : 1;
>> > > unsigned int do_timer_last : 1;
>> > > unsigned int got_idle_tick : 1;
>> >
>> > I don't think this is a good idea at all.
>> >
>> > Please see https://lkml.org/lkml/2017/11/21/384 for example.
>> [ZJ] Thanks for this sharing. Looks like, this patch fall into the
>> case of
>> "Maybe".
>
> This patch falls into the case 'pointless' because it adds extra
> storage
[ZJ] 1 bit vs 1 bit. no more.

> for no benefit at all.
[ZJ] tick_stopped is returned by the tick_nohz_tick_stopped() which is
bool.
The benefit is no any potiential type conversion could be minded.

>
> Thanks,
>
> tglx

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