Messages in this thread Patch in this message | | | Date | Tue, 01 Jan 2008 17:55:53 +0100 | From | Eric Dumazet <> | Subject | [PATCH] X86 : Introduce DEFINE_PER_CPU_PAGE_ALIGNED() macro for x86 arch to shrink percpu section |
| |
Hi Ingo
Here is a patch against linux-2.6-x86 git
Thank you
[PATCH] X86 : Introduce DEFINE_PER_CPU_PAGE_ALIGNED() macro for x86 arch to shrink percpu section
While examining holes in percpu section I found this :
c0659008 D per_cpu__cpu_number c065900c D per_cpu__irq_regs <BIG HOLE of about 4000 bytes> c065a000 D per_cpu__gdt_page c065b000 d per_cpu__next_check
This is because gdt_page is a percpu variable, defined with a page alignement, and linker is doing its job.
I introduced a new macro DEFINE_PER_CPU_PAGE_ALIGNED() to avoid wasting this space. All page aligned variables are put in a separate subsection .data.percpu.page_aligned
This macro is defined for x86/generic architectures only but could be added to other arches if needed.
Before patch :
# size -A vmlinux | grep percpu .data.percpu 26144 3227328512
After patch :
# size -A vmlinux | grep percpu .data.percpu 22048 3227328512
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
arch/x86/kernel/cpu/common.c | 2 +- arch/x86/kernel/vmlinux_32.lds.S | 1 + include/asm-generic/percpu.h | 4 ++++ include/asm-generic/vmlinux.lds.h | 1 + include/asm-x86/percpu_32.h | 4 ++++ include/asm-x86/percpu_64.h | 4 ++++ 6 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index e2fcf20..a262d4c 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -21,7 +21,7 @@ #include "cpu.h" -DEFINE_PER_CPU(struct gdt_page, gdt_page) = { .gdt = { +DEFINE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page) = { .gdt = { [GDT_ENTRY_KERNEL_CS] = { 0x0000ffff, 0x00cf9a00 }, [GDT_ENTRY_KERNEL_DS] = { 0x0000ffff, 0x00cf9200 }, [GDT_ENTRY_DEFAULT_USER_CS] = { 0x0000ffff, 0x00cffa00 }, diff --git a/arch/x86/kernel/vmlinux_32.lds.S b/arch/x86/kernel/vmlinux_32.lds.S index 7d72cce..b579e8b 100644 --- a/arch/x86/kernel/vmlinux_32.lds.S +++ b/arch/x86/kernel/vmlinux_32.lds.S @@ -182,6 +182,7 @@ SECTIONS . = ALIGN(4096); .data.percpu : AT(ADDR(.data.percpu) - LOAD_OFFSET) { __per_cpu_start = .; + *(.data.percpu.page_aligned) *(.data.percpu) *(.data.percpu.shared_aligned) __per_cpu_end = .; diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h index d85172e..6c89cda 100644 --- a/include/asm-generic/percpu.h +++ b/include/asm-generic/percpu.h @@ -14,6 +14,10 @@ extern unsigned long __per_cpu_offset[NR_CPUS]; #define DEFINE_PER_CPU(type, name) \ __attribute__((__section__(".data.percpu"))) __typeof__(type) per_cpu__##name +#define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \ + __attribute__((__section__(".data.percpu.page_aligned"))) \ + __typeof__(type) per_cpu__##name + #define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ __attribute__((__section__(".data.percpu.shared_aligned"))) \ __typeof__(type) per_cpu__##name \ diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 9f584cc..68aaf68 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -259,6 +259,7 @@ . = ALIGN(align); \ __per_cpu_start = .; \ .data.percpu : AT(ADDR(.data.percpu) - LOAD_OFFSET) { \ + *(.data.percpu.page_aligned) \ *(.data.percpu) \ *(.data.percpu.shared_aligned) \ } \ diff --git a/include/asm-x86/percpu_32.h b/include/asm-x86/percpu_32.h index a7ebd43..a515897 100644 --- a/include/asm-x86/percpu_32.h +++ b/include/asm-x86/percpu_32.h @@ -54,6 +54,10 @@ 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_PAGE_ALIGNED(type, name) \ + __attribute__((__section__(".data.percpu.page_aligned"))) \ + __typeof__(type) per_cpu__##name + #define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ __attribute__((__section__(".data.percpu.shared_aligned"))) \ __typeof__(type) per_cpu__##name \ diff --git a/include/asm-x86/percpu_64.h b/include/asm-x86/percpu_64.h index 5abd482..9949008 100644 --- a/include/asm-x86/percpu_64.h +++ b/include/asm-x86/percpu_64.h @@ -20,6 +20,10 @@ #define DEFINE_PER_CPU(type, name) \ __attribute__((__section__(".data.percpu"))) __typeof__(type) per_cpu__##name +#define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \ + __attribute__((__section__(".data.percpu.page_aligned"))) \ + __typeof__(type) per_cpu__##name + #define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ __attribute__((__section__(".data.percpu.shared_aligned"))) \ __typeof__(type) per_cpu__##name \ | |