From: Fenghua Yu per cpu data section contains two types of data. One set which is exclusively accessed by the local cpu and the other set which is per cpu, but also shared by remote cpus. In the current kernel, these two sets are not clearely separated out. This can potentially cause the same data cacheline shared between the two sets of data, which will result in unnecessary bouncing of the cacheline between cpus. One way to fix the problem is to cacheline align the remotely accessed per cpu data, both at the beginning and at the end. Because of the padding at both ends, this will likely cause some memory wastage and also the interface to achieve this is not clean. This patch: Moves the remotely accessed per cpu data (which is currently marked as ____cacheline_aligned_in_smp) into a different section, where all the data elements are cacheline aligned. And as such, this differentiates the local only data and remotely accessed data cleanly. Signed-off-by: Fenghua Yu Acked-by: Suresh Siddha Cc: Rusty Russell Cc: Christoph Lameter Cc: Cc: "Luck, Tony" Cc: Andi Kleen Signed-off-by: Andrew Morton --- arch/alpha/kernel/vmlinux.lds.S | 5 +---- arch/arm/kernel/vmlinux.lds.S | 1 + arch/cris/arch-v32/vmlinux.lds.S | 5 +---- arch/frv/kernel/vmlinux.lds.S | 5 +---- arch/i386/kernel/vmlinux.lds.S | 1 + arch/ia64/kernel/vmlinux.lds.S | 1 + arch/m32r/kernel/vmlinux.lds.S | 5 +---- arch/mips/kernel/vmlinux.lds.S | 5 +---- arch/parisc/kernel/vmlinux.lds.S | 7 +++---- arch/powerpc/kernel/vmlinux.lds.S | 1 + arch/ppc/kernel/vmlinux.lds.S | 5 +---- arch/s390/kernel/vmlinux.lds.S | 5 +---- arch/sh/kernel/vmlinux.lds.S | 5 +---- arch/sh64/kernel/vmlinux.lds.S | 5 ++++- arch/sparc/kernel/vmlinux.lds.S | 5 +---- arch/sparc64/kernel/vmlinux.lds.S | 6 ++---- arch/x86_64/kernel/vmlinux.lds.S | 6 ++---- arch/xtensa/kernel/vmlinux.lds.S | 5 +---- include/asm-generic/percpu.h | 8 ++++++++ include/asm-generic/vmlinux.lds.h | 8 ++++++++ include/asm-i386/percpu.h | 5 +++++ include/asm-ia64/percpu.h | 10 ++++++++++ include/asm-powerpc/percpu.h | 7 +++++++ include/asm-s390/percpu.h | 7 +++++++ include/asm-sparc64/percpu.h | 7 +++++++ include/asm-x86_64/percpu.h | 7 +++++++ 26 files changed, 84 insertions(+), 53 deletions(-) diff -puN arch/alpha/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 arch/alpha/kernel/vmlinux.lds.S --- a/arch/alpha/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 +++ a/arch/alpha/kernel/vmlinux.lds.S @@ -69,10 +69,7 @@ SECTIONS . = ALIGN(8); SECURITY_INIT - . = ALIGN(8192); - __per_cpu_start = .; - .data.percpu : { *(.data.percpu) } - __per_cpu_end = .; + PERCPU(8192) . = ALIGN(2*8192); __init_end = .; diff -puN arch/arm/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 arch/arm/kernel/vmlinux.lds.S --- a/arch/arm/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 +++ a/arch/arm/kernel/vmlinux.lds.S @@ -66,6 +66,7 @@ SECTIONS . = ALIGN(4096); __per_cpu_start = .; *(.data.percpu) + *(.data.percpu.shared_aligned) __per_cpu_end = .; #ifndef CONFIG_XIP_KERNEL __init_begin = _stext; diff -puN arch/cris/arch-v32/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 arch/cris/arch-v32/vmlinux.lds.S --- a/arch/cris/arch-v32/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 +++ a/arch/cris/arch-v32/vmlinux.lds.S @@ -91,10 +91,7 @@ SECTIONS } SECURITY_INIT - . = ALIGN (8192); - __per_cpu_start = .; - .data.percpu : { *(.data.percpu) } - __per_cpu_end = .; + PERCPU(8192) #ifdef CONFIG_BLK_DEV_INITRD .init.ramfs : { diff -puN arch/frv/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 arch/frv/kernel/vmlinux.lds.S --- a/arch/frv/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 +++ a/arch/frv/kernel/vmlinux.lds.S @@ -57,10 +57,7 @@ SECTIONS __alt_instructions_end = .; .altinstr_replacement : { *(.altinstr_replacement) } - . = ALIGN(4096); - __per_cpu_start = .; - .data.percpu : { *(.data.percpu) } - __per_cpu_end = .; + PERCPU(4096) #ifdef CONFIG_BLK_DEV_INITRD . = ALIGN(4096); diff -puN arch/i386/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 arch/i386/kernel/vmlinux.lds.S --- a/arch/i386/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 +++ a/arch/i386/kernel/vmlinux.lds.S @@ -183,6 +183,7 @@ SECTIONS .data.percpu : AT(ADDR(.data.percpu) - LOAD_OFFSET) { __per_cpu_start = .; *(.data.percpu) + *(.data.percpu.shared_aligned) __per_cpu_end = .; } . = ALIGN(4096); diff -puN arch/ia64/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 arch/ia64/kernel/vmlinux.lds.S --- a/arch/ia64/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 +++ a/arch/ia64/kernel/vmlinux.lds.S @@ -206,6 +206,7 @@ SECTIONS { __per_cpu_start = .; *(.data.percpu) + *(.data.percpu.shared_aligned) __per_cpu_end = .; } . = __phys_per_cpu_start + PERCPU_PAGE_SIZE; /* ensure percpu data fits diff -puN arch/m32r/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 arch/m32r/kernel/vmlinux.lds.S --- a/arch/m32r/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 +++ a/arch/m32r/kernel/vmlinux.lds.S @@ -110,10 +110,7 @@ SECTIONS __initramfs_end = .; #endif - . = ALIGN(4096); - __per_cpu_start = .; - .data.percpu : { *(.data.percpu) } - __per_cpu_end = .; + PERCPU(4096) . = ALIGN(4096); __init_end = .; /* freed after init ends here */ diff -puN arch/mips/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 arch/mips/kernel/vmlinux.lds.S --- a/arch/mips/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 +++ a/arch/mips/kernel/vmlinux.lds.S @@ -119,10 +119,7 @@ SECTIONS .init.ramfs : { *(.init.ramfs) } __initramfs_end = .; #endif - . = ALIGN(_PAGE_SIZE); - __per_cpu_start = .; - .data.percpu : { *(.data.percpu) } - __per_cpu_end = .; + PERCPU(_PAGE_SIZE) . = ALIGN(_PAGE_SIZE); __init_end = .; /* freed after init ends here */ diff -puN arch/parisc/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 arch/parisc/kernel/vmlinux.lds.S --- a/arch/parisc/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 +++ a/arch/parisc/kernel/vmlinux.lds.S @@ -181,10 +181,9 @@ SECTIONS .init.ramfs : { *(.init.ramfs) } __initramfs_end = .; #endif - . = ALIGN(ASM_PAGE_SIZE); - __per_cpu_start = .; - .data.percpu : { *(.data.percpu) } - __per_cpu_end = .; + + PERCPU(ASM_PAGE_SIZE) + . = ALIGN(ASM_PAGE_SIZE); __init_end = .; /* freed after init ends here */ diff -puN arch/powerpc/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 arch/powerpc/kernel/vmlinux.lds.S --- a/arch/powerpc/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 +++ a/arch/powerpc/kernel/vmlinux.lds.S @@ -143,6 +143,7 @@ SECTIONS .data.percpu : { __per_cpu_start = .; *(.data.percpu) + *(.data.percpu.shared_aligned) __per_cpu_end = .; } diff -puN arch/ppc/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 arch/ppc/kernel/vmlinux.lds.S --- a/arch/ppc/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 +++ a/arch/ppc/kernel/vmlinux.lds.S @@ -130,10 +130,7 @@ SECTIONS __ftr_fixup : { *(__ftr_fixup) } __stop___ftr_fixup = .; - . = ALIGN(4096); - __per_cpu_start = .; - .data.percpu : { *(.data.percpu) } - __per_cpu_end = .; + PERCPU(4096) #ifdef CONFIG_BLK_DEV_INITRD . = ALIGN(4096); diff -puN arch/s390/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 arch/s390/kernel/vmlinux.lds.S --- a/arch/s390/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 +++ a/arch/s390/kernel/vmlinux.lds.S @@ -107,10 +107,7 @@ SECTIONS . = ALIGN(2); __initramfs_end = .; #endif - . = ALIGN(4096); - __per_cpu_start = .; - .data.percpu : { *(.data.percpu) } - __per_cpu_end = .; + PERCPU(4096) . = ALIGN(4096); __init_end = .; /* freed after init ends here */ diff -puN arch/sh/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 arch/sh/kernel/vmlinux.lds.S --- a/arch/sh/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 +++ a/arch/sh/kernel/vmlinux.lds.S @@ -60,10 +60,7 @@ SECTIONS . = ALIGN(PAGE_SIZE); __nosave_end = .; - . = ALIGN(PAGE_SIZE); - __per_cpu_start = .; - .data.percpu : { *(.data.percpu) } - __per_cpu_end = .; + PERCPU(PAGE_SIZE) .data.cacheline_aligned : { *(.data.cacheline_aligned) } _edata = .; /* End of data section */ diff -puN arch/sh64/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 arch/sh64/kernel/vmlinux.lds.S --- a/arch/sh64/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 +++ a/arch/sh64/kernel/vmlinux.lds.S @@ -87,7 +87,10 @@ SECTIONS . = ALIGN(PAGE_SIZE); __per_cpu_start = .; - .data.percpu : C_PHYS(.data.percpu) { *(.data.percpu) } + .data.percpu : C_PHYS(.data.percpu) { + *(.data.percpu) + *(.data.percpu.shared_aligned) + } __per_cpu_end = . ; .data.cacheline_aligned : C_PHYS(.data.cacheline_aligned) { *(.data.cacheline_aligned) } diff -puN arch/sparc/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 arch/sparc/kernel/vmlinux.lds.S --- a/arch/sparc/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 +++ a/arch/sparc/kernel/vmlinux.lds.S @@ -65,10 +65,7 @@ SECTIONS __initramfs_end = .; #endif - . = ALIGN(4096); - __per_cpu_start = .; - .data.percpu : { *(.data.percpu) } - __per_cpu_end = .; + PERCPU(4096) . = ALIGN(4096); __init_end = .; . = ALIGN(32); diff -puN arch/sparc64/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 arch/sparc64/kernel/vmlinux.lds.S --- a/arch/sparc64/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 +++ a/arch/sparc64/kernel/vmlinux.lds.S @@ -90,10 +90,8 @@ SECTIONS __initramfs_end = .; #endif - . = ALIGN(PAGE_SIZE); - __per_cpu_start = .; - .data.percpu : { *(.data.percpu) } - __per_cpu_end = .; + PERCPU(PAGE_SIZE) + . = ALIGN(PAGE_SIZE); __init_end = .; __bss_start = .; diff -puN arch/x86_64/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 arch/x86_64/kernel/vmlinux.lds.S --- a/arch/x86_64/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 +++ a/arch/x86_64/kernel/vmlinux.lds.S @@ -210,10 +210,8 @@ SECTIONS __initramfs_end = .; #endif - . = ALIGN(4096); - __per_cpu_start = .; - .data.percpu : AT(ADDR(.data.percpu) - LOAD_OFFSET) { *(.data.percpu) } - __per_cpu_end = .; + PERCPU(4096) + . = ALIGN(4096); __init_end = .; diff -puN arch/xtensa/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 arch/xtensa/kernel/vmlinux.lds.S --- a/arch/xtensa/kernel/vmlinux.lds.S~define-new-percpu-interface-for-shared-data-version-4 +++ a/arch/xtensa/kernel/vmlinux.lds.S @@ -190,10 +190,7 @@ SECTIONS __initramfs_end = .; #endif - . = ALIGN(4096); - __per_cpu_start = .; - .data.percpu : { *(.data.percpu) } - __per_cpu_end = .; + PERCPU(4096) /* We need this dummy segment here */ diff -puN include/asm-generic/percpu.h~define-new-percpu-interface-for-shared-data-version-4 include/asm-generic/percpu.h --- a/include/asm-generic/percpu.h~define-new-percpu-interface-for-shared-data-version-4 +++ a/include/asm-generic/percpu.h @@ -14,6 +14,11 @@ extern unsigned long __per_cpu_offset[NR #define DEFINE_PER_CPU(type, name) \ __attribute__((__section__(".data.percpu"))) __typeof__(type) per_cpu__##name +#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ + __attribute__((__section__(".data.percpu.shared_aligned"))) \ + __typeof__(type) per_cpu__##name \ + ____cacheline_aligned_in_smp + /* var is in discarded region: offset to particular copy we want */ #define per_cpu(var, cpu) (*({ \ extern int simple_identifier_##var(void); \ @@ -34,6 +39,9 @@ do { \ #define DEFINE_PER_CPU(type, name) \ __typeof__(type) per_cpu__##name +#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ + DEFINE_PER_CPU(type, name) + #define per_cpu(var, cpu) (*((void)(cpu), &per_cpu__##var)) #define __get_cpu_var(var) per_cpu__##var #define __raw_get_cpu_var(var) per_cpu__##var diff -puN include/asm-generic/vmlinux.lds.h~define-new-percpu-interface-for-shared-data-version-4 include/asm-generic/vmlinux.lds.h --- a/include/asm-generic/vmlinux.lds.h~define-new-percpu-interface-for-shared-data-version-4 +++ a/include/asm-generic/vmlinux.lds.h @@ -267,3 +267,11 @@ *(.initcall7.init) \ *(.initcall7s.init) +#define PERCPU(align) \ + . = ALIGN(align); \ + __per_cpu_start = .; \ + .data.percpu : AT(ADDR(.data.percpu) - LOAD_OFFSET) { \ + *(.data.percpu) \ + *(.data.percpu.shared_aligned) \ + } \ + __per_cpu_end = .; diff -puN include/asm-i386/percpu.h~define-new-percpu-interface-for-shared-data-version-4 include/asm-i386/percpu.h --- a/include/asm-i386/percpu.h~define-new-percpu-interface-for-shared-data-version-4 +++ a/include/asm-i386/percpu.h @@ -54,6 +54,11 @@ extern unsigned long __per_cpu_offset[]; #define DEFINE_PER_CPU(type, name) \ __attribute__((__section__(".data.percpu"))) __typeof__(type) per_cpu__##name +#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ + __attribute__((__section__(".data.percpu.shared_aligned"))) \ + __typeof__(type) per_cpu__##name \ + ____cacheline_aligned_in_smp + /* We can use this directly for local CPU (faster). */ DECLARE_PER_CPU(unsigned long, this_cpu_off); diff -puN include/asm-ia64/percpu.h~define-new-percpu-interface-for-shared-data-version-4 include/asm-ia64/percpu.h --- a/include/asm-ia64/percpu.h~define-new-percpu-interface-for-shared-data-version-4 +++ a/include/asm-ia64/percpu.h @@ -29,6 +29,16 @@ __attribute__((__section__(".data.percpu"))) \ __SMALL_ADDR_AREA __typeof__(type) per_cpu__##name +#ifdef CONFIG_SMP +#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ + __attribute__((__section__(".data.percpu.shared_aligned"))) \ + __SMALL_ADDR_AREA __typeof__(type) per_cpu__##name \ + ____cacheline_aligned_in_smp +#else +#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ + DEFINE_PER_CPU(type, name) +#endif + /* * Pretty much a literal copy of asm-generic/percpu.h, except that percpu_modcopy() is an * external routine, to avoid include-hell. diff -puN include/asm-powerpc/percpu.h~define-new-percpu-interface-for-shared-data-version-4 include/asm-powerpc/percpu.h --- a/include/asm-powerpc/percpu.h~define-new-percpu-interface-for-shared-data-version-4 +++ a/include/asm-powerpc/percpu.h @@ -20,6 +20,11 @@ #define DEFINE_PER_CPU(type, name) \ __attribute__((__section__(".data.percpu"))) __typeof__(type) per_cpu__##name +#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ + __attribute__((__section__(".data.percpu.shared_aligned"))) \ + __typeof__(type) per_cpu__##name \ + ____cacheline_aligned_in_smp + /* var is in discarded region: offset to particular copy we want */ #define per_cpu(var, cpu) (*RELOC_HIDE(&per_cpu__##var, __per_cpu_offset(cpu))) #define __get_cpu_var(var) (*RELOC_HIDE(&per_cpu__##var, __my_cpu_offset())) @@ -40,6 +45,8 @@ extern void setup_per_cpu_areas(void); #define DEFINE_PER_CPU(type, name) \ __typeof__(type) per_cpu__##name +#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ + DEFINE_PER_CPU(type, name) #define per_cpu(var, cpu) (*((void)(cpu), &per_cpu__##var)) #define __get_cpu_var(var) per_cpu__##var diff -puN include/asm-s390/percpu.h~define-new-percpu-interface-for-shared-data-version-4 include/asm-s390/percpu.h --- a/include/asm-s390/percpu.h~define-new-percpu-interface-for-shared-data-version-4 +++ a/include/asm-s390/percpu.h @@ -41,6 +41,11 @@ extern unsigned long __per_cpu_offset[NR __attribute__((__section__(".data.percpu"))) \ __typeof__(type) per_cpu__##name +#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ + __attribute__((__section__(".data.percpu.shared_aligned"))) \ + __typeof__(type) per_cpu__##name \ + ____cacheline_aligned_in_smp + #define __get_cpu_var(var) __reloc_hide(var,S390_lowcore.percpu_offset) #define __raw_get_cpu_var(var) __reloc_hide(var,S390_lowcore.percpu_offset) #define per_cpu(var,cpu) __reloc_hide(var,__per_cpu_offset[cpu]) @@ -59,6 +64,8 @@ do { \ #define DEFINE_PER_CPU(type, name) \ __typeof__(type) per_cpu__##name +#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ + DEFINE_PER_CPU(type, name) #define __get_cpu_var(var) __reloc_hide(var,0) #define __raw_get_cpu_var(var) __reloc_hide(var,0) diff -puN include/asm-sparc64/percpu.h~define-new-percpu-interface-for-shared-data-version-4 include/asm-sparc64/percpu.h --- a/include/asm-sparc64/percpu.h~define-new-percpu-interface-for-shared-data-version-4 +++ a/include/asm-sparc64/percpu.h @@ -18,6 +18,11 @@ extern unsigned long __per_cpu_shift; #define DEFINE_PER_CPU(type, name) \ __attribute__((__section__(".data.percpu"))) __typeof__(type) per_cpu__##name +#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ + __attribute__((__section__(".data.percpu.shared_aligned"))) \ + __typeof__(type) per_cpu__##name \ + ____cacheline_aligned_in_smp + register unsigned long __local_per_cpu_offset asm("g5"); /* var is in discarded region: offset to particular copy we want */ @@ -38,6 +43,8 @@ do { \ #define real_setup_per_cpu_areas() do { } while (0) #define DEFINE_PER_CPU(type, name) \ __typeof__(type) per_cpu__##name +#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ + DEFINE_PER_CPU(type, name) #define per_cpu(var, cpu) (*((void)cpu, &per_cpu__##var)) #define __get_cpu_var(var) per_cpu__##var diff -puN include/asm-x86_64/percpu.h~define-new-percpu-interface-for-shared-data-version-4 include/asm-x86_64/percpu.h --- a/include/asm-x86_64/percpu.h~define-new-percpu-interface-for-shared-data-version-4 +++ a/include/asm-x86_64/percpu.h @@ -20,6 +20,11 @@ #define DEFINE_PER_CPU(type, name) \ __attribute__((__section__(".data.percpu"))) __typeof__(type) per_cpu__##name +#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ + __attribute__((__section__(".data.percpu.shared_aligned"))) \ + __typeof__(type) per_cpu__##name \ + ____cacheline_internodealigned_in_smp + /* var is in discarded region: offset to particular copy we want */ #define per_cpu(var, cpu) (*({ \ extern int simple_identifier_##var(void); \ @@ -46,6 +51,8 @@ extern void setup_per_cpu_areas(void); #define DEFINE_PER_CPU(type, name) \ __typeof__(type) per_cpu__##name +#define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ + DEFINE_PER_CPU(type, name) #define per_cpu(var, cpu) (*((void)(cpu), &per_cpu__##var)) #define __get_cpu_var(var) per_cpu__##var _