From: yuankuiz@codeaurora.org
To: Thomas Gleixner <tglx@linutronix.de>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
Linux PM <linux-pm@vger.kernel.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Frederic Weisbecker <fweisbec@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>, Len Brown <len.brown@intel.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linux-pm-owner@vger.kernel.org
Subject: Re: [PATCH] time: tick-sched: use bool for tick_stopped
Date: Tue, 10 Apr 2018 18:07:17 +0800 [thread overview]
Message-ID: <a7d6dddd7d4f9fdc0be8f94251af237f@codeaurora.org> (raw)
In-Reply-To: <alpine.DEB.2.21.1804101110080.2058@nanos.tec.linutronix.de>
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
next prev parent reply other threads:[~2018-04-10 10:07 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-10 7:33 Subject: [PATCH] [PATCH] time: tick-sched: use bool for tick_stopped yuankuiz
2018-04-10 7:45 ` yuankuiz
2018-04-10 8:51 ` yuankuiz
2018-04-10 8:54 ` yuankuiz
2018-04-10 7:55 ` Subject: [PATCH] " Thomas Gleixner
2018-04-10 8:12 ` yuankuiz
2018-04-10 8:00 ` Rafael J. Wysocki
2018-04-10 8:15 ` yuankuiz
2018-04-10 9:10 ` Thomas Gleixner
2018-04-10 10:07 ` yuankuiz [this message]
2018-04-10 11:06 ` Thomas Gleixner
2018-04-10 14:08 ` yuankuiz
2018-04-10 14:49 ` yuankuiz
2018-04-10 23:09 ` yuankuiz
2018-04-10 23:20 ` yuankuiz
2018-04-20 1:47 ` yuankuiz
2018-04-20 6:44 ` yuankuiz
2018-04-20 19:24 ` Joe Perches
2018-04-25 7:01 ` yuankuiz
2018-04-10 11:26 ` Peter Zijlstra
2018-04-10 12:07 ` Thomas Gleixner
2018-04-10 12:26 ` Peter Zijlstra
2018-04-10 12:33 ` Subject: [PATCH] " Peter Zijlstra
2018-04-10 15:14 ` Joe Perches
2018-04-10 16:30 ` Peter Zijlstra
2018-04-10 15:41 ` [PATCH] checkpatch: whinge about bool bitfields Joe Perches
2018-04-10 18:19 ` [PATCH] checkpatch: Add a --strict test for structs with bool member definitions Joe Perches
2018-04-10 21:39 ` Andrew Morton
2018-04-10 21:53 ` Joe Perches
2018-04-10 22:00 ` Andrew Morton
2018-04-11 8:15 ` Peter Zijlstra
2018-04-11 16:29 ` Andrew Morton
2018-04-11 16:51 ` Joe Perches
2018-04-12 6:22 ` Julia Lawall
2018-04-12 6:42 ` Joe Perches
2018-04-12 7:03 ` Julia Lawall
2018-04-12 8:13 ` Peter Zijlstra
2018-04-14 21:19 ` Julia Lawall
2018-04-17 9:07 ` yuankuiz
2018-04-18 18:38 ` Joe Perches
2018-04-19 4:40 ` Julia Lawall
2018-04-19 4:51 ` Joe Perches
2018-04-19 5:16 ` Julia Lawall
2018-04-19 6:48 ` yuankuiz
2018-04-19 10:42 ` yuankuiz
2018-04-20 1:31 ` yuankuiz
2018-04-11 17:00 ` Peter Zijlstra
2018-04-12 7:47 ` Ingo Molnar
2018-04-12 8:11 ` Peter Zijlstra
2018-04-12 9:35 ` Andrea Parri
2018-04-12 11:50 ` Peter Zijlstra
2018-04-12 12:01 ` Joe Perches
2018-04-12 12:08 ` Peter Zijlstra
2018-04-12 12:38 ` Joe Perches
2018-04-12 16:47 ` Andrew Morton
2018-04-12 11:52 ` Kalle Valo
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