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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID:
 <OSZPR01MB8798F324AB66D9B62495E9088B8AA@OSZPR01MB8798.jpnprd01.prod.outlook.com>
Date: Fri, 9 May 2025 08:39:51 +0000
From: "Shaopeng Tan (Fujitsu)" <tan.shaopeng@...itsu.com>
To: 'James Morse' <james.morse@....com>, "x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC: Reinette Chatre <reinette.chatre@...el.com>, Thomas Gleixner
	<tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov
	<bp@...en8.de>, H Peter Anvin <hpa@...or.com>, Babu Moger
	<Babu.Moger@....com>, "shameerali.kolothum.thodi@...wei.com"
	<shameerali.kolothum.thodi@...wei.com>, D Scott Phillips OS
	<scott@...amperecomputing.com>, "carl@...amperecomputing.com"
	<carl@...amperecomputing.com>, "lcherian@...vell.com" <lcherian@...vell.com>,
	"bobo.shaobowang@...wei.com" <bobo.shaobowang@...wei.com>,
	"baolin.wang@...ux.alibaba.com" <baolin.wang@...ux.alibaba.com>, Jamie Iles
	<quic_jiles@...cinc.com>, Xin Hao <xhao@...ux.alibaba.com>,
	"peternewman@...gle.com" <peternewman@...gle.com>, "dfustini@...libre.com"
	<dfustini@...libre.com>, "amitsinght@...vell.com" <amitsinght@...vell.com>,
	David Hildenbrand <david@...hat.com>, Rex Nie <rex.nie@...uarmicro.com>, Dave
 Martin <dave.martin@....com>, Koba Ko <kobak@...dia.com>, Shanker Donthineni
	<sdonthineni@...dia.com>, "fenghuay@...dia.com" <fenghuay@...dia.com>, "Yury
 Norov [NVIDIA]" <yury.norov@...il.com>
Subject: RE: [PATCH v10 04/30] x86/resctrl: Optimize
 cpumask_any_housekeeping()

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.

Best regards,
Shaopeng TAN

> +	if (tick_nohz_full_enabled()) {
> +		cpu = cpumask_any_andnot_but(mask, tick_nohz_full_mask,
> exclude_cpu);
> +		if (cpu < nr_cpu_ids)
> +			return cpu;
> +	}
> 
> -	if (hk_cpu < nr_cpu_ids)
> -		cpu = hk_cpu;
> -
> -	return cpu;
> +	return cpumask_any_but(mask, exclude_cpu);
>  }
> 
>  struct rdt_fs_context {
> --
> 2.39.5