dynamically use the irqbalance

[Dong_Wei]

Hi, all.
  I want to dynamically use irqbalance on X86 processor. My design is 
like the following:
  1) if we boot kernel with "noirqbalance", then irqbalance is always 
disabled.
  2) if we boot kernel without "noirqbalance", we can enable/disable 
irqbalance in runtime.

I create a proc_fs entry /proc/sys/kernel/irqbalance
This symbol I adding is in file arch/i386/kernel/io_apic.c
/proc/sys/kernel/irqbalance = 0 /* disable irqbalance in runtime */
/proc/sys/kernel/irqbalance = 1 /* enable irqbalance in runtime */

The core function is like the following:
irqbalance_irq_flag = -1; /* this is the last time irqbalance used */
irqbalance_enable = 1; /* set it to enable by default */
static int balanced_irq(void *unused)
{
    int i;
    unsigned long prev_balance_time = jiffies;
    long time_remaining = balanced_irq_interval;

    daemonize("kirqd");

    /* push everything to CPU 0 to give us a starting point.  */
    for (i = 0 ; i < NR_IRQS ; i++) {
        irq_desc[i].pending_mask = cpumask_of_cpu(0);
        set_pending_irq(i, cpumask_of_cpu(0));
    }

    for ( ; ; ) {
        time_remaining = schedule_timeout_interruptible(time_remaining);
        try_to_freeze();
        if(irqbalance_enable) {
             if (time_after(jiffies, 
prev_balance_time+balanced_irq_interval)) {
                 preempt_disable();
                 do_irq_balance();
                 prev_balance_time = jiffies;
                 time_remaining = balanced_irq_interval;
                 preempt_enable();
                 irqbalance_irq_flag = 1;
             }
         } else if (irqbalance_irq_flag != 0) {
             /* Is it SAFE to do so? */
             for (i = 0 ; i < NR_IRQS ; i++)
                 set_pending_irq(i, cpumask_of_cpu(0));
             irqbalance_irq_flag = 0;
         }
     }
     return 0;
}

When we change /proc/sys/kernel/irqbalance from 1 to 0, I move all the 
irqs to CPU#0, Is it safe to do so? or will lead to some very dangerous 
thing?

Please help me to review my design, thanks in advance.

BTW: I can't join the linux-kernel maillist, for our mail server now has 
 some problems. If anyone replies my mail. Pls CC to me.


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