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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 /include/linux/percpu.h | |
| parent | 75d3bce2fc0a80f435fe12f2c9ed2632c8ac29e4 (diff) | |
| download | lwn-63cc8c75156462d4b42cbdd76c293b7eee7ddbfe.tar.gz lwn-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>
Diffstat (limited to 'include/linux/percpu.h')
| -rw-r--r-- | include/linux/percpu.h | 7 |
1 files changed, 7 insertions, 0 deletions
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) |