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authorEric Dumazet <dada1@cosmosbay.com>2008-05-12 15:44:40 +0200
committerThomas Gleixner <tglx@linutronix.de>2008-05-25 07:03:46 +0200
commit63cc8c75156462d4b42cbdd76c293b7eee7ddbfe (patch)
treee014b4c61399f8f74347352e6ea76ddf1502dcfa /include
parent75d3bce2fc0a80f435fe12f2c9ed2632c8ac29e4 (diff)
downloadop-kernel-dev-63cc8c75156462d4b42cbdd76c293b7eee7ddbfe.zip
op-kernel-dev-63cc8c75156462d4b42cbdd76c293b7eee7ddbfe.tar.gz
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>
Diffstat (limited to 'include')
-rw-r--r--include/asm-generic/vmlinux.lds.h1
-rw-r--r--include/linux/percpu.h7
2 files changed, 8 insertions, 0 deletions
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index f054778..69e5c11 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 4cdd393..2edacc8 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)
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