[PATCH v3 23/59] x86/percpu: Move preempt_count next to current_task

Peter Zijlstra
2022-09-15T11:43:29Z

From: Thomas Gleixner <tglx@linutronix.de>

Add preempt_count to pcpu_hot, since it is once of the most used
per-cpu variables.

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/preempt.h | 27 ++++++++++++++-------------
arch/x86/kernel/cpu/common.c | 8 +-------
3 files changed, 16 insertions(+), 20 deletions(-)

--- a/arch/x86/include/asm/current.h
+++ b/arch/x86/include/asm/current.h
@@ -15,6 +15,7 @@ struct pcpu_hot {
union {
struct {
struct task_struct *current_task;
+ int preempt_count;
};
u8 pad[64];
};
--- a/arch/x86/include/asm/preempt.h
+++ b/arch/x86/include/asm/preempt.h
@@ -4,11 +4,11 @@

#include <asm/rmwcc.h>
#include <asm/percpu.h>
+#include <asm/current.h>
+
#include <linux/thread_info.h>
#include <linux/static_call_types.h>

-DECLARE_PER_CPU(int, __preempt_count);
-
/* We use the MSB mostly because its available */
#define PREEMPT_NEED_RESCHED 0x80000000

@@ -24,7 +24,7 @@ DECLARE_PER_CPU(int, __preempt_count);
*/
static __always_inline int preempt_count(void)
{
- return raw_cpu_read_4(__preempt_count) & ~PREEMPT_NEED_RESCHED;
+ return raw_cpu_read_4(pcpu_hot.preempt_count) & ~PREEMPT_NEED_RESCHED;
}

static __always_inline void preempt_count_set(int pc)
@@ -32,10 +32,10 @@ static __always_inline void preempt_coun
int old, new;

do {
- old = raw_cpu_read_4(__preempt_count);
+ old = raw_cpu_read_4(pcpu_hot.preempt_count);
new = (old & PREEMPT_NEED_RESCHED) |
(pc & ~PREEMPT_NEED_RESCHED);
- } while (raw_cpu_cmpxchg_4(__preempt_count, old, new) != old);
+ } while (raw_cpu_cmpxchg_4(pcpu_hot.preempt_count, old, new) != old);
}

/*
@@ -44,7 +44,7 @@ static __always_inline void preempt_coun
#define init_task_preempt_count(p) do { } while (0)

#define init_idle_preempt_count(p, cpu) do { \
- per_cpu(__preempt_count, (cpu)) = PREEMPT_DISABLED; \
+ per_cpu(pcpu_hot.preempt_count, (cpu)) = PREEMPT_DISABLED; \
} while (0)

/*
@@ -58,17 +58,17 @@ static __always_inline void preempt_coun

static __always_inline void set_preempt_need_resched(void)
{
- raw_cpu_and_4(__preempt_count, ~PREEMPT_NEED_RESCHED);
+ raw_cpu_and_4(pcpu_hot.preempt_count, ~PREEMPT_NEED_RESCHED);
}

static __always_inline void clear_preempt_need_resched(void)
{
- raw_cpu_or_4(__preempt_count, PREEMPT_NEED_RESCHED);
+ raw_cpu_or_4(pcpu_hot.preempt_count, PREEMPT_NEED_RESCHED);
}

static __always_inline bool test_preempt_need_resched(void)
{
- return !(raw_cpu_read_4(__preempt_count) & PREEMPT_NEED_RESCHED);
+ return !(raw_cpu_read_4(pcpu_hot.preempt_count) & PREEMPT_NEED_RESCHED);
}

/*
@@ -77,12 +77,12 @@ static __always_inline bool test_preempt

static __always_inline void __preempt_count_add(int val)
{
- raw_cpu_add_4(__preempt_count, val);
+ raw_cpu_add_4(pcpu_hot.preempt_count, val);
}

static __always_inline void __preempt_count_sub(int val)
{
- raw_cpu_add_4(__preempt_count, -val);
+ raw_cpu_add_4(pcpu_hot.preempt_count, -val);
}

/*
@@ -92,7 +92,8 @@ static __always_inline void __preempt_co
*/
static __always_inline bool __preempt_count_dec_and_test(void)
{
- return GEN_UNARY_RMWcc("decl", __preempt_count, e, __percpu_arg([var]));
+ return GEN_UNARY_RMWcc("decl", pcpu_hot.preempt_count, e,
+ __percpu_arg([var]));
}

/*
@@ -100,7 +101,7 @@ static __always_inline bool __preempt_co
*/
static __always_inline bool should_resched(int preempt_offset)
{
- return unlikely(raw_cpu_read_4(__preempt_count) == preempt_offset);
+ return unlikely(raw_cpu_read_4(pcpu_hot.preempt_count) == preempt_offset);
}

#ifdef CONFIG_PREEMPTION
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -2002,6 +2002,7 @@ static __init int setup_clearcpuid(char

DEFINE_PER_CPU_ALIGNED(struct pcpu_hot, pcpu_hot) = {
.current_task = &init_task,
+ .preempt_count = INIT_PREEMPT_COUNT,
};
EXPORT_PER_CPU_SYMBOL(pcpu_hot);

@@ -2010,13 +2011,9 @@ DEFINE_PER_CPU_FIRST(struct fixed_percpu
fixed_percpu_data) __aligned(PAGE_SIZE) __visible;
EXPORT_PER_CPU_SYMBOL_GPL(fixed_percpu_data);

-
DEFINE_PER_CPU(void *, hardirq_stack_ptr);
DEFINE_PER_CPU(bool, hardirq_stack_inuse);

-DEFINE_PER_CPU(int, __preempt_count) = INIT_PREEMPT_COUNT;
-EXPORT_PER_CPU_SYMBOL(__preempt_count);
-
DEFINE_PER_CPU(unsigned long, cpu_current_top_of_stack) = TOP_OF_INIT_STACK;

static void wrmsrl_cstar(unsigned long val)
@@ -2069,9 +2066,6 @@ void syscall_init(void)

#else /* CONFIG_X86_64 */

-DEFINE_PER_CPU(int, __preempt_count) = INIT_PREEMPT_COUNT;
-EXPORT_PER_CPU_SYMBOL(__preempt_count);
-
/*
* On x86_32, vm86 modifies tss.sp0, so sp0 isn't a reliable way to find
* the top of the kernel stack. Use an extra percpu variable to track the