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    Subject[patch 1/7] Increase default reserve percpu area
    SLUB now requires a portion of the per cpu reserve. There are on average
    about 70 real slabs on a system (aliases do not count) and each needs 12 bytes
    of per cpu space. Thats 840 bytes. In debug mode all slabs will be real slabs
    which will make us end up with 150 -> 1800.

    Things work fine without this patch but then slub will reduce the percpu reserve
    for modules.

    Percpu data must be available regardless if modules are in use or not. So get
    rid of the #ifdef CONFIG_MODULES.

    Make the size of the percpu area dependant on the size of a machine word. That
    way we have larger sizes for 64 bit machines. 64 bit machines need more percpu
    memory since the pointer and counters may have double the size. Plus there is
    lots of memory available on 64 bit.

    Signed-off-by: Christoph Lameter <>

    Index: linux-2.6/include/linux/percpu.h
    --- linux-2.6.orig/include/linux/percpu.h 2008-11-05 12:05:46.000000000 -0600
    +++ linux-2.6/include/linux/percpu.h 2008-11-05 14:29:15.000000000 -0600
    @@ -44,7 +44,7 @@
    extern unsigned int percpu_reserve;
    /* Enough to cover all DEFINE_PER_CPUs in kernel, including modules. */
    #ifndef PERCPU_AREA_SIZE
    -#define PERCPU_RESERVE_SIZE 8192
    +#define PERCPU_RESERVE_SIZE (sizeof(unsigned long) * 2500)

    #define PERCPU_AREA_SIZE \
    (__per_cpu_end - __per_cpu_start + percpu_reserve)

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      Last update: 2008-11-06 00:27    [W:0.045 / U:11.760 seconds]
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