From mboxrd@z Thu Jan 1 00:00:00 1970 From: yuankuiz@codeaurora.org Subject: Re: [PATCH] time: tick-sched: use bool for tick_stopped Date: Tue, 10 Apr 2018 18:07:17 +0800 Message-ID: References: <891d4f632fbff5052e11f2d0b6fac35d@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Thomas Gleixner Cc: "Rafael J. Wysocki" , Linux PM , "Rafael J. Wysocki" , Frederic Weisbecker , Peter Zijlstra , Ingo Molnar , Len Brown , Linux Kernel Mailing List , linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org 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, wrote: >> > > From: John Zhao >> > > >> > > 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 >> > > --- >> > > 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