linux-kernel - [PATCH] x86: convert a few more per-CPU items to read-mostly ones

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Date:	Tue, 04 Nov 2014 08:26:42 +0000
From:	"Jan Beulich" <JBeulich@...e.com>
To:	<mingo@...e.hu>, <tglx@...utronix.de>, <hpa@...or.com>
Cc:	<linux-kernel@...r.kernel.org>
Subject: [PATCH] x86: convert a few more per-CPU items to read-mostly
 ones

Both this_cpu_off and cpu_info aren't getting modified post boot, yet
are being accessed on enough code paths that grouping them with other
frequently read items seems desirable. For cpu_info this at the same
time implies removing the cache line alignment (which afaict became
pointless when it got converted to per-CPU data years ago).

Signed-off-by: Jan Beulich <jbeulich@...e.com>
---
 arch/x86/include/asm/percpu.h    |    2 +-
 arch/x86/include/asm/processor.h |    4 ++--
 arch/x86/kernel/setup_percpu.c   |    2 +-
 arch/x86/kernel/smpboot.c        |    2 +-
 4 files changed, 5 insertions(+), 5 deletions(-)

--- 3.18-rc3/arch/x86/include/asm/percpu.h
+++ 3.18-rc3-x86-cpu-info-read-mostly/arch/x86/include/asm/percpu.h
@@ -522,7 +522,7 @@ static inline int x86_this_cpu_variable_
 #include <asm-generic/percpu.h>
 
 /* We can use this directly for local CPU (faster). */
-DECLARE_PER_CPU(unsigned long, this_cpu_off);
+DECLARE_PER_CPU_READ_MOSTLY(unsigned long, this_cpu_off);
 
 #endif /* !__ASSEMBLY__ */
 
--- 3.18-rc3/arch/x86/include/asm/processor.h
+++ 3.18-rc3-x86-cpu-info-read-mostly/arch/x86/include/asm/processor.h
@@ -127,7 +127,7 @@ struct cpuinfo_x86 {
 	/* Index into per_cpu list: */
 	u16			cpu_index;
 	u32			microcode;
-} __attribute__((__aligned__(SMP_CACHE_BYTES)));
+};
 
 #define X86_VENDOR_INTEL	0
 #define X86_VENDOR_CYRIX	1
@@ -151,7 +151,7 @@ extern __u32			cpu_caps_cleared[NCAPINTS
 extern __u32			cpu_caps_set[NCAPINTS];
 
 #ifdef CONFIG_SMP
-DECLARE_PER_CPU_SHARED_ALIGNED(struct cpuinfo_x86, cpu_info);
+DECLARE_PER_CPU_READ_MOSTLY(struct cpuinfo_x86, cpu_info);
 #define cpu_data(cpu)		per_cpu(cpu_info, cpu)
 #else
 #define cpu_info		boot_cpu_data
--- 3.18-rc3/arch/x86/kernel/setup_percpu.c
+++ 3.18-rc3-x86-cpu-info-read-mostly/arch/x86/kernel/setup_percpu.c
@@ -30,7 +30,7 @@ EXPORT_PER_CPU_SYMBOL(cpu_number);
 #define BOOT_PERCPU_OFFSET 0
 #endif
 
-DEFINE_PER_CPU(unsigned long, this_cpu_off) = BOOT_PERCPU_OFFSET;
+DEFINE_PER_CPU_READ_MOSTLY(unsigned long, this_cpu_off) = BOOT_PERCPU_OFFSET;
 EXPORT_PER_CPU_SYMBOL(this_cpu_off);
 
 unsigned long __per_cpu_offset[NR_CPUS] __read_mostly = {
--- 3.18-rc3/arch/x86/kernel/smpboot.c
+++ 3.18-rc3-x86-cpu-info-read-mostly/arch/x86/kernel/smpboot.c
@@ -99,7 +99,7 @@ EXPORT_PER_CPU_SYMBOL(cpu_core_map);
 DEFINE_PER_CPU_READ_MOSTLY(cpumask_var_t, cpu_llc_shared_map);
 
 /* Per CPU bogomips and other parameters */
-DEFINE_PER_CPU_SHARED_ALIGNED(struct cpuinfo_x86, cpu_info);
+DEFINE_PER_CPU_READ_MOSTLY(struct cpuinfo_x86, cpu_info);
 EXPORT_PER_CPU_SYMBOL(cpu_info);
 
 atomic_t init_deasserted;



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