On Wed, 2007-03-28 at 03:39, Jack Steiner wrote:
> This patch adds an optional method for purging the TLB on SN IA64 systems.
> The change should not affect any non-SN system.
>
> Signed-off-by: Jack Steiner <[EMAIL PROTECTED]>
>
> ---
>
> +void
> +smp_flush_tlb_cpumask (cpumask_t xcpumask)
> +{
> + unsigned short counts[NR_CPUS];
> + cpumask_t cpumask = xcpumask;
> + int count, mycpu, cpu, flush_mycpu = 0;
> +
> + preempt_disable();
> + mycpu = smp_processor_id();
> +
> + for_each_cpu_mask(cpu, cpumask) {
> + counts[cpu] = per_cpu(local_flush_count, cpu);
> + mb();
> + if (cpu == mycpu)
> + flush_mycpu = 1;
> + else
> + smp_send_local_flush_tlb(cpu);
> + }
> +
> + if (flush_mycpu)
> + smp_local_flush_tlb();
> +
> + for_each_cpu_mask(cpu, cpumask) {
> + count = 0;
> + while(counts[cpu] == per_cpu(local_flush_count, cpu)) {
Due to 64k offset of percpu data, the same percpu variable on different
CPUs are very likely to be on the same cacheline of some levels of
cache.
So I think the operation on local_flush_count may be very cache
unfriendly...
Zou Nan hai
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