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    Subject[PATCH] [33/58] x86_64: Avoid too many remote cpu references due to /proc/stat
    Date

    From: Ravikiran G Thirumalai <kiran@scalex86.org>
    Too many remote cpu references due to /proc/stat.

    On x86_64, with newer kernel versions, kstat_irqs is a bit of a problem.
    On every call to kstat_irqs, the process brings in per-cpu data from all
    online cpus. Doing this for NR_IRQS, which is now 256 + 32 * NR_CPUS
    results in (256+32*63) * 63 remote cpu references on a 64 cpu config.
    /proc/stat is parsed by common commands like top, who etc, causing
    lots of cacheline transfers

    This statistic seems useless. Other 'big iron' arches disable this.
    Can we disable computing/reporting this statistic? This piece of
    statistic is not human readable on x86_64 anymore,

    If not, can we optimize computing this statistic so as to avoid
    too many remote references (patch to follow)

    Signed-off-by: Ravikiran Thirumalai <kiran@scalex86.org>
    Signed-off-by: Andi Kleen <ak@suse.de>

    ---
    fs/proc/proc_misc.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    Index: linux/fs/proc/proc_misc.c
    ===================================================================
    --- linux.orig/fs/proc/proc_misc.c
    +++ linux/fs/proc/proc_misc.c
    @@ -499,7 +499,8 @@ static int show_stat(struct seq_file *p,
    }
    seq_printf(p, "intr %llu", (unsigned long long)sum);

    -#if !defined(CONFIG_PPC64) && !defined(CONFIG_ALPHA) && !defined(CONFIG_IA64)
    +#if !defined(CONFIG_PPC64) && !defined(CONFIG_ALPHA) && !defined(CONFIG_IA64) \
    + && !defined(CONFIG_X86_64)
    for (i = 0; i < NR_IRQS; i++)
    seq_printf(p, " %u", kstat_irqs(i));
    #endif
    -
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