Re: [PATCH v10 04/30] x86/resctrl: Optimize cpumask_any_housekeeping()

[Yury Norov]

On Fri, May 09, 2025 at 08:39:51AM +0000, Shaopeng Tan (Fujitsu) wrote:
> Hello James,
> 
> > From: "Yury Norov [NVIDIA]" <yury.norov@xxxxxxxxx>
> > 
> > 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@xxxxxxx>
> > Reviewed-by: James Morse <james.morse@xxxxxxx>
> > Reviewed-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
> > Signed-off-by: Yury Norov [NVIDIA] <yury.norov@xxxxxxxxx>
> > Signed-off-by: James Morse <james.morse@xxxxxxx>
> > ---
> >  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.

Thanks,
Yury