From: Fenghua Yu <fenghua.yu@intel.com>
To: Andy Lutomirski <luto@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
H Peter Anvin <hpa@zytor.com>, Ashok Raj <ashok.raj@intel.com>,
Tony Luck <tony.luck@intel.com>,
Ravi V Shankar <ravi.v.shankar@intel.com>,
linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>
Subject: Re: [PATCH v4 3/5] x86/umwait: Add sysfs interface to control umwait C0.2 state
Date: Mon, 17 Jun 2019 15:51:46 -0700 [thread overview]
Message-ID: <20190617225146.GE217081@romley-ivt3.sc.intel.com> (raw)
In-Reply-To: <CALCETrXnOKo3daWp-oSwaVZagQ_iP7SHCbpoB2VioWhRds5gqw@mail.gmail.com>
On Mon, Jun 17, 2019 at 03:59:28PM -0700, Andy Lutomirski wrote:
> On Mon, Jun 17, 2019 at 3:57 PM Fenghua Yu <fenghua.yu@intel.com> wrote:
> >
> > On Sun, Jun 09, 2019 at 09:26:29PM -0700, Andy Lutomirski wrote:
> > > On Sun, Jun 9, 2019 at 9:14 PM Fenghua Yu <fenghua.yu@intel.com> wrote:
> > > >
> > > > On Sat, Jun 08, 2019 at 03:52:03PM -0700, Andy Lutomirski wrote:
> > > > > On Fri, Jun 7, 2019 at 3:10 PM Fenghua Yu <fenghua.yu@intel.com> wrote:
> > > > > >
> > > > > > C0.2 state in umwait and tpause instructions can be enabled or disabled
> > > > > > on a processor through IA32_UMWAIT_CONTROL MSR register.
> > > > > >
> > > > >
> > > > > > +static u32 get_umwait_control_c02(void)
> > > > > > +{
> > > > > > + return umwait_control_cached & MSR_IA32_UMWAIT_CONTROL_C02;
> > > > > > +}
> > > > > > +
> > > > > > +static u32 get_umwait_control_max_time(void)
> > > > > > +{
> > > > > > + return umwait_control_cached & MSR_IA32_UMWAIT_CONTROL_MAX_TIME;
> > > > > > +}
> > > > > > +
> > > > >
> > > > > I'm not convinced that these helpers make the code any more readable.
> > > >
> > > > The helpers reduce length of statements that call them. Otherwise, all of
> > > > the statements would be easily over 80 characters.
> > > >
> > > > Plus, each of the helpers is called multiple places in #0003 and #0004.
> > > > So the helpers make the patches smaller and cleaner.
> > > >
> > >
> > > I was imagining things like:
> > >
> > > umwait_control_cached &= ~MSR_IA32_UMWAIT_CONTROL_C02;
> > > if (whatever condition)
> > > umwait_control_cached |= MSR_IA32_UMWAIT_CONTROL_C02;
> > > umwait_control_cached &= ~MSR_IA32_UMWAIT_CONTROL_MAX_TIME;
> > > umwait_control_cached |= new_max_time;
> >
> > How about this statement?
> > With the helpers:
> > umwait_control_cached = max_time | get_umwait_control_c02();
> > If there is no helpers, the above statement will need two statements:
> > umwait_control_cached &= ~MSR_IA32_UMWAIT_CONTROL_MAX_TIME;
> > umwait_control_cached |= max_time;
> >
> > Another example:
> > With the helpers:
> > if (umwait_control_c02 == get_umwait_control_c02())
> > If no helpers, the above statement will be long:
> > if (umwait_control_c02 == (umwait_control_cached & MSR_IA32_UMWAIT_CONTROL_C02_DISABLED))
> >
> > There are quite a few places like above examples.
> >
> > The helpers can reduce the length of those long lines and make code more
> > readable and shorter, right?
> >
> > Can I still keep the helpers?
> >
>
> Sure, unless someone else objects.
Thank you very much for your advice!
-Fenghua
next prev parent reply other threads:[~2019-06-17 23:01 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-07 22:00 [PATCH v4 0/5] x86/umwait: Enable user wait instructions Fenghua Yu
2019-06-07 22:00 ` [PATCH v4 1/5] x86/cpufeatures: Enumerate " Fenghua Yu
2019-06-07 22:00 ` [PATCH v4 2/5] x86/umwait: Initialize umwait control values Fenghua Yu
2019-06-08 22:52 ` Andy Lutomirski
2019-06-10 4:13 ` Fenghua Yu
2019-06-10 4:27 ` Andy Lutomirski
2019-06-11 20:46 ` Thomas Gleixner
2019-06-17 20:46 ` Fenghua Yu
2019-06-18 5:43 ` Thomas Gleixner
2019-06-11 8:50 ` Peter Zijlstra
2019-06-11 17:04 ` Fenghua Yu
2019-06-07 22:00 ` [PATCH v4 3/5] x86/umwait: Add sysfs interface to control umwait C0.2 state Fenghua Yu
2019-06-08 22:50 ` Andy Lutomirski
2019-06-10 3:53 ` Fenghua Yu
2019-06-10 4:24 ` Andy Lutomirski
2019-06-10 6:02 ` Fenghua Yu
2019-06-10 13:41 ` Andy Lutomirski
2019-06-17 20:27 ` Fenghua Yu
2019-06-17 23:02 ` Andy Lutomirski
2019-06-17 23:11 ` Fenghua Yu
2019-06-17 23:41 ` Andy Lutomirski
2019-06-18 0:00 ` Fenghua Yu
2019-06-18 0:19 ` Andy Lutomirski
2019-06-18 2:32 ` Fenghua Yu
2019-06-08 22:52 ` Andy Lutomirski
2019-06-10 4:04 ` Fenghua Yu
2019-06-10 4:26 ` Andy Lutomirski
2019-06-17 22:48 ` Fenghua Yu
2019-06-17 22:59 ` Andy Lutomirski
2019-06-17 22:51 ` Fenghua Yu [this message]
2019-06-11 8:54 ` Peter Zijlstra
2019-06-11 16:04 ` Andy Lutomirski
2019-06-11 17:27 ` Peter Zijlstra
2019-06-17 15:14 ` Andy Lutomirski
2019-06-17 18:11 ` Fenghua Yu
2019-06-07 22:00 ` [PATCH v4 4/5] x86/umwait: Add sysfs interface to control umwait maximum time Fenghua Yu
2019-06-07 22:00 ` [PATCH v4 5/5] x86/umwait: Document umwait control sysfs interfaces Fenghua Yu
2019-06-11 9:01 ` [PATCH v4 0/5] x86/umwait: Enable user wait instructions Peter Zijlstra
2019-06-11 17:37 ` Fenghua Yu
2019-06-17 14:19 ` Peter Zijlstra
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