[PATCH v3 24/59] x86/percpu: Move cpu_number next to current_task

Peter Zijlstra
2022-09-15T11:45:25Z

From: Thomas Gleixner <tglx@linutronix.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@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.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