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

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Message-Id: <20250508171858.9197-5-james.morse@arm.com>
Date: Thu,  8 May 2025 17:18:32 +0000
From: James Morse <james.morse@....com>
To: x86@...nel.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>,
	James Morse <james.morse@....com>,
	shameerali.kolothum.thodi@...wei.com,
	D Scott Phillips OS <scott@...amperecomputing.com>,
	carl@...amperecomputing.com,
	lcherian@...vell.com,
	bobo.shaobowang@...wei.com,
	tan.shaopeng@...itsu.com,
	baolin.wang@...ux.alibaba.com,
	Jamie Iles <quic_jiles@...cinc.com>,
	Xin Hao <xhao@...ux.alibaba.com>,
	peternewman@...gle.com,
	dfustini@...libre.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,
	"Yury Norov [NVIDIA]" <yury.norov@...il.com>
Subject: [PATCH v10 04/30] x86/resctrl: Optimize cpumask_any_housekeeping()

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);
+	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