• Eric Dumazet's avatar
    percpu: introduce DEFINE_PER_CPU_PAGE_ALIGNED() macro · 63cc8c75
    Eric Dumazet authored
    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: default avatarEric Dumazet <dada1@cosmosbay.com>
    Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    63cc8c75
vmlinux_32.lds.S 5.32 KB