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| author | Eric Dumazet <dada1@cosmosbay.com> | 2008-05-12 15:44:40 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2008-05-25 07:03:46 +0200 |
| commit | 63cc8c75156462d4b42cbdd76c293b7eee7ddbfe (patch) | |
| tree | e014b4c61399f8f74347352e6ea76ddf1502dcfa | |
| parent | Merge git://git.kernel.org/pub/scm/linux/kernel/git/sfrench/cifs-2.6 (diff) | |
| download | linux-63cc8c75156462d4b42cbdd76c293b7eee7ddbfe.tar.xz linux-63cc8c75156462d4b42cbdd76c293b7eee7ddbfe.zip | |
percpu: introduce DEFINE_PER_CPU_PAGE_ALIGNED() macro
While examining holes in percpu section I found this :
c05f5000 D per_cpu__current_task
c05f5000 D __per_cpu_start
c05f5004 D per_cpu__cpu_number
c05f5008 D per_cpu__irq_regs
c05f500c d per_cpu__cpu_devices
c05f5040 D per_cpu__cyc2ns
<Big Hole of about 4000 bytes>
c05f6000 d per_cpu__cpuid4_info
c05f6004 d per_cpu__cache_kobject
c05f6008 d per_cpu__index_kobject
<Big Hole of about 4000 bytes>
c05f7000 D per_cpu__gdt_page
This is because gdt_page is a percpu variable, defined with
a page alignement, and linker is doing its job, two times because of .o
nesting in the build process.
I introduced a new macro DEFINE_PER_CPU_PAGE_ALIGNED() to avoid
wasting this space. All page aligned variables (only one at this time)
are put in a separate
subsection .data.percpu.page_aligned, at the very begining of percpu zone.
Before patch , on a x86_32 machine :
.data.percpu 30232 3227471872
.data.percpu 22168 3227471872
Thats 8064 bytes saved for each CPU.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 2 | ||||
| -rw-r--r-- | arch/x86/kernel/vmlinux_32.lds.S | 1 | ||||
| -rw-r--r-- | include/asm-generic/vmlinux.lds.h | 1 | ||||
| -rw-r--r-- | include/linux/percpu.h | 7 |
4 files changed, 10 insertions, 1 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index d0463a946247..b2f54fafb8bc 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 ce5ed083a1e9..0f7c29a8c4ea 100644 --- a/arch/x86/kernel/vmlinux_32.lds.S +++ b/arch/x86/kernel/vmlinux_32.lds.S @@ -189,6 +189,7 @@ SECTIONS . = ALIGN(PAGE_SIZE); .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/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index f054778e916c..69e5c1182fde 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -348,6 +348,7 @@ . = 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/linux/percpu.h b/include/linux/percpu.h index 4cdd393e71e1..2edacc8e6b8b 100644 --- a/include/linux/percpu.h +++ b/include/linux/percpu.h @@ -23,12 +23,19 @@ __attribute__((__section__(SHARED_ALIGNED_SECTION))) \ PER_CPU_ATTRIBUTES __typeof__(type) per_cpu__##name \ ____cacheline_aligned_in_smp + +#define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \ + __attribute__((__section__(".data.percpu.page_aligned"))) \ + PER_CPU_ATTRIBUTES __typeof__(type) per_cpu__##name #else #define DEFINE_PER_CPU(type, name) \ PER_CPU_ATTRIBUTES __typeof__(type) per_cpu__##name #define DEFINE_PER_CPU_SHARED_ALIGNED(type, name) \ DEFINE_PER_CPU(type, name) + +#define DEFINE_PER_CPU_PAGE_ALIGNED(type, name) \ + DEFINE_PER_CPU(type, name) #endif #define EXPORT_PER_CPU_SYMBOL(var) EXPORT_SYMBOL(per_cpu__##var) |