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    Subject[RFC patch] Use IPI_shortcut for lapic timer broadcast
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    Hello,

    We need to use IPI shortcut to send lapic timer broadcast
    to avoid the latency of sending IPI one bye one on systems with many
    logical processors when NO_HZ is disabled.
    Without this patch,I have seen upstream kernel with RHEL 5 kernel
    config boot hang .

    The patch also changes physflat_send_IPI_all to IPI shortcut mode.

    Please review, and apply.

    **The patch is enclosed in text attachment*
    **Using web client to send the patch* *
    **below is for review, please apply attached patch*/

    Thanks,
    Luming


    Signed-off-by: Yu Luming <luming.yu@intel.com>

    apic.c | 4 +++-
    apic_flat_64.c | 7 ++++++-
    2 files changed, 9 insertions(+), 2 deletions(-)

    --- linux-2.6.30-rc6/arch/x86/kernel/apic/apic.c.0 2009-06-28
    20:22:55.000000000 -0600
    +++ linux-2.6.30-rc6/arch/x86/kernel/apic/apic.c 2009-06-29
    00:21:44.000000000 -0600
    @@ -419,7 +419,9 @@
    static void lapic_timer_broadcast(const struct cpumask *mask)
    {
    #ifdef CONFIG_SMP
    - apic->send_IPI_mask(mask, LOCAL_TIMER_VECTOR);
    + if (cpus_empty(*mask))
    + return;
    + apic->send_IPI_all(LOCAL_TIMER_VECTOR);
    #endif
    }

    --- linux-2.6.30-rc6/arch/x86/kernel/apic/apic_flat_64.c.0 2009-06-29
    00:13:26.000000000 -0600
    +++ linux-2.6.30-rc6/arch/x86/kernel/apic/apic_flat_64.c 2009-06-29
    00:11:23.000000000 -0600
    @@ -274,7 +274,12 @@

    static void physflat_send_IPI_all(int vector)
    {
    - physflat_send_IPI_mask(cpu_online_mask, vector);
    + if (vector == NMI_VECTOR) {
    + physflat_send_IPI_mask(cpu_online_mask, vector);
    + } else {
    + __default_send_IPI_shortcut(APIC_DEST_ALLINC,
    + vector, apic->dest_logical);
    + }
    }

    static unsigned int physflat_cpu_mask_to_apicid(const struct cpumask *cpumask)[unhandled content-type:application/octet-stream]
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      Last update: 2009-06-29 08:59    [W:0.020 / U:1.712 seconds]
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