linux-kernel - [tip: x86/cache] x86/resctrl: Optimize cpumask_any

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Message-ID: <174747618489.406.16388124501789539670.tip-bot2@tip-bot2>
Date: Sat, 17 May 2025 10:03:04 -0000
From: "tip-bot2 for Yury Norov [NVIDIA]" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Yury Norov [NVIDIA]" <yury.norov@...il.com>,
 James Morse <james.morse@....com>, "Borislav Petkov (AMD)" <bp@...en8.de>,
 Reinette Chatre <reinette.chatre@...el.com>,
 Shaopeng Tan <tan.shaopeng@...fujitsu.com>, Fenghua Yu <fenghuay@...dia.com>,
 Tony Luck <tony.luck@...el.com>, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/cache] x86/resctrl: Optimize cpumask_any_housekeeping()

The following commit has been merged into the x86/cache branch of tip:

Commit-ID:     94f7531430285b4ec600693f7222c2ca29bd7472
Gitweb:        https://git.kernel.org/tip/94f7531430285b4ec600693f7222c2ca29bd7472
Author:        Yury Norov [NVIDIA] <yury.norov@...il.com>
AuthorDate:    Thu, 15 May 2025 16:58:34 
Committer:     Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Thu, 15 May 2025 20:53:26 +02:00

x86/resctrl: Optimize cpumask_any_housekeeping()

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.

Signed-off-by: Yury Norov [NVIDIA] <yury.norov@...il.com>
Signed-off-by: James Morse <james.morse@....com>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Reviewed-by: James Morse <james.morse@....com>
Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
Reviewed-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
Reviewed-by: Fenghua Yu <fenghuay@...dia.com>
Tested-by: Fenghua Yu <fenghuay@...dia.com>
Tested-by: James Morse <james.morse@....com>
Tested-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
Tested-by: Tony Luck <tony.luck@...el.com>
Link: https://lore.kernel.org/20250515165855.31452-5-james.morse@arm.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 eaae996..25b61e4 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 (hk_cpu < nr_cpu_ids)
-		cpu = hk_cpu;
+	if (tick_nohz_full_enabled()) {
+		cpu = cpumask_any_andnot_but(mask, tick_nohz_full_mask, exclude_cpu);
+		if (cpu < nr_cpu_ids)
+			return cpu;
+	}
 
-	return cpu;
+	return cpumask_any_but(mask, exclude_cpu);
 }
 
 struct rdt_fs_context {