linux-kernel - RE: [PATCH v10 04/30] x86/resctrl: Optimize cpumask_any

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Message-ID:
 <OSZPR01MB8798309112398B9D78A76B8D8B96A@OSZPR01MB8798.jpnprd01.prod.outlook.com>
Date: Tue, 13 May 2025 02:42:19 +0000
From: "Shaopeng Tan (Fujitsu)" <tan.shaopeng@...itsu.com>
To: 'Yury Norov' <yury.norov@...il.com>
CC: 'James Morse' <james.morse@....com>, "x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Reinette
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Subject: RE: [PATCH v10 04/30] x86/resctrl: Optimize
 cpumask_any_housekeeping()

Hello Yury,

> Subject: Re: [PATCH v10 04/30] x86/resctrl: Optimize
> cpumask_any_housekeeping()
> 
> On Fri, May 09, 2025 at 08:39:51AM +0000, Shaopeng Tan (Fujitsu) wrote:
> > Hello James,
> >
> > > From: "Yury Norov [NVIDIA]" <yury.norov@...il.com>
> > >
> > > With the lack of cpumask_any_andnot_but(),
> > > cpumask_any_housekeeping() has to abuse cpumask_nth() functions.
> > >
> > > Update cpumask_any_housekeeping() to use the new
> cpumask_any_but()
> > > and cpumask_any_andnot_but(). These two functions understand
> > > RESCTRL_PICK_ANY_CPU, which simplifies
> cpumask_any_housekeeping()
> > > significantly.
> > >
> > > Tested-by: James Morse <james.morse@....com>
> > > Reviewed-by: James Morse <james.morse@....com>
> > > Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
> > > Signed-off-by: Yury Norov [NVIDIA] <yury.norov@...il.com>
> > > Signed-off-by: James Morse <james.morse@....com>
> > > ---
> > >  arch/x86/kernel/cpu/resctrl/internal.h | 28
> > > +++++++-------------------
> > >  1 file changed, 7 insertions(+), 21 deletions(-)
> > >
> > > diff --git a/arch/x86/kernel/cpu/resctrl/internal.h
> > > b/arch/x86/kernel/cpu/resctrl/internal.h
> > > index eaae99602b61..25b61e466715 100644
> > > --- a/arch/x86/kernel/cpu/resctrl/internal.h
> > > +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> > > @@ -47,30 +47,16 @@
> > >  static inline unsigned int
> > >  cpumask_any_housekeeping(const struct cpumask *mask, int
> > > exclude_cpu) {
> > > -	unsigned int cpu, hk_cpu;
> > > -
> > > -	if (exclude_cpu == RESCTRL_PICK_ANY_CPU)
> > > -		cpu = cpumask_any(mask);
> > > -	else
> > > -		cpu = cpumask_any_but(mask, exclude_cpu);
> > > -
> > > -	/* Only continue if tick_nohz_full_mask has been initialized. */
> > > -	if (!tick_nohz_full_enabled())
> > > -		return cpu;
> > > -
> > > -	/* If the CPU picked isn't marked nohz_full nothing more needs doing.
> > > */
> > > -	if (cpu < nr_cpu_ids && !tick_nohz_full_cpu(cpu))
> > > -		return cpu;
> > > +	unsigned int cpu;
> > >
> > >  	/* Try to find a CPU that isn't nohz_full to use in preference */
> > > -	hk_cpu = cpumask_nth_andnot(0, mask, tick_nohz_full_mask);
> > > -	if (hk_cpu == exclude_cpu)
> > > -		hk_cpu = cpumask_nth_andnot(1, mask,
> > > tick_nohz_full_mask);
> >
> > It seems that the cpumask_nth_andnot() function is no longer used
> > anywhere, so it's better to remove it from ./include/linux/cpumask.h.
> 
> Yeah. Can you send a patch after this series will get merged? I'll move it with my
> branch then.

Okay, I will send a patch after this series is merged.
Reviewed-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>

Best regards,
Shaopeng TAN