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    SubjectRe: [PATCH] alloc_percpu() fails to allocate percpu data
    Andrew Morton a écrit :
    > On Wed, 27 Feb 2008 11:59:32 -0800 (PST)
    > Christoph Lameter <> wrote:
    >> Any decision made on what to do about this one? Mike or I can
    >> repost the per cpu allocator against mm? The fix by Eric could be used
    >> in the interim for 2.6.24?
    > I suppose I'll merge Eric's patch when I've tested it fully (well, as fully
    > as I test stuff).
    > It'd be nice to get that cache_line_size()/L1_CACHE_BYTES/L1_CACHE_ALIGN()
    > mess sorted out. If it's a mess - I _think_ it is?

    Just coming back from hollidays, sorry for the delay.

    I can provide a patch so that L1_CACHE_BYTES is not anymore a compile time
    constant if you want, but I am not sure it is worth the trouble ? (and this
    certainly not 2.6.{24|25} stuff :) )

    Current situation :

    L1_CACHE_BYTES is known at compile time, and can be quite large (128 bytes),
    while cache_line_size() gives the real cache line size selected at boot time
    given the hardware capabilities.

    If L1_CACHE_BYTES is not anymore a constant, compiler will also uses plain
    divides to compute L1_CACHE_ALIGN()

    Maybe uses of L1_CACHE_ALIGN() in fastpath would 'force' us to not only
    declare a cache_line_size() but also a cache_line_size_{mask|shift}() so that
    x86 could use :

    #define L1_CACHE_ALIGN(x) ((((x)+cache_line_mask())) >> cache_line_shift())

    #define L1_CACHE_BYTES (cache_line_size())

    But I am not sure we want to play these games (we must also make sure nothing
    in the tree wants a constant L1_CACHE_BYTES and replace by SMP_CACHE_BYTES)

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