linux-kernel - [PATCH v3 24/59] x86/percpu: Move cpu_number next to current

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Message-ID: <20220915111145.387678283@infradead.org>
Date:   Thu, 15 Sep 2022 13:11:03 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org, x86@...nel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Andrew Cooper <Andrew.Cooper3@...rix.com>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Johannes Wikner <kwikner@...z.ch>,
        Alyssa Milburn <alyssa.milburn@...ux.intel.com>,
        Jann Horn <jannh@...gle.com>, "H.J. Lu" <hjl.tools@...il.com>,
        Joao Moreira <joao.moreira@...el.com>,
        Joseph Nuzman <joseph.nuzman@...el.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Juergen Gross <jgross@...e.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH v3 24/59] x86/percpu: Move cpu_number next to current_task

From: Thomas Gleixner <tglx@...utronix.de>

Also add cpu_number to the pcpu_hot structure, it is often referenced
and this cacheline is there.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/include/asm/current.h |    1 +
 arch/x86/include/asm/smp.h     |   12 +++++-------
 arch/x86/kernel/setup_percpu.c |    5 +----
 3 files changed, 7 insertions(+), 11 deletions(-)

--- a/arch/x86/include/asm/current.h
+++ b/arch/x86/include/asm/current.h
@@ -16,6 +16,7 @@ struct pcpu_hot {
 		struct {
 			struct task_struct	*current_task;
 			int			preempt_count;
+			int			cpu_number;
 		};
 		u8	pad[64];
 	};
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -3,10 +3,10 @@
 #define _ASM_X86_SMP_H
 #ifndef __ASSEMBLY__
 #include <linux/cpumask.h>
-#include <asm/percpu.h>
 
-#include <asm/thread_info.h>
 #include <asm/cpumask.h>
+#include <asm/current.h>
+#include <asm/thread_info.h>
 
 extern int smp_num_siblings;
 extern unsigned int num_processors;
@@ -19,7 +19,6 @@ DECLARE_PER_CPU_READ_MOSTLY(cpumask_var_
 DECLARE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_l2c_shared_map);
 DECLARE_PER_CPU_READ_MOSTLY(u16, cpu_llc_id);
 DECLARE_PER_CPU_READ_MOSTLY(u16, cpu_l2c_id);
-DECLARE_PER_CPU_READ_MOSTLY(int, cpu_number);
 
 static inline struct cpumask *cpu_llc_shared_mask(int cpu)
 {
@@ -160,11 +159,10 @@ asmlinkage __visible void smp_reboot_int
 
 /*
  * This function is needed by all SMP systems. It must _always_ be valid
- * from the initial startup. We map APIC_BASE very early in page_setup(),
- * so this is correct in the x86 case.
+ * from the initial startup.
  */
-#define raw_smp_processor_id()  this_cpu_read(cpu_number)
-#define __smp_processor_id() __this_cpu_read(cpu_number)
+#define raw_smp_processor_id()  this_cpu_read(pcpu_hot.cpu_number)
+#define __smp_processor_id() __this_cpu_read(pcpu_hot.cpu_number)
 
 #ifdef CONFIG_X86_32
 extern int safe_smp_processor_id(void);
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -23,9 +23,6 @@
 #include <asm/cpu.h>
 #include <asm/stackprotector.h>
 
-DEFINE_PER_CPU_READ_MOSTLY(int, cpu_number);
-EXPORT_PER_CPU_SYMBOL(cpu_number);
-
 #ifdef CONFIG_X86_64
 #define BOOT_PERCPU_OFFSET ((unsigned long)__per_cpu_load)
 #else
@@ -172,7 +169,7 @@ void __init setup_per_cpu_areas(void)
 	for_each_possible_cpu(cpu) {
 		per_cpu_offset(cpu) = delta + pcpu_unit_offsets[cpu];
 		per_cpu(this_cpu_off, cpu) = per_cpu_offset(cpu);
-		per_cpu(cpu_number, cpu) = cpu;
+		per_cpu(pcpu_hot.cpu_number, cpu) = cpu;
 		setup_percpu_segment(cpu);
 		/*
 		 * Copy data used in early init routines from the