Re: [PATCH v4 1/1] rps: core implementation

[Tom Herbert <therbert@google.com>]

On Fri, Nov 20, 2009 at 3:39 PM, David Miller <davem@davemloft.net> wrote:
> From: Tom Herbert <therbert@google.com>
> Date: Fri, 20 Nov 2009 15:28:58 -0800
>
>> +             /* Schedule NAPI for backlog device */
>> +             if (napi_schedule_prep(&queue->backlog)) {
>> +                     if (cpu != smp_processor_id()) {
>> +                             cpu_set(cpu,
>> +                                 get_cpu_var(rps_remote_softirq_cpus));
>> +                             __raise_softirq_irqoff(NET_RX_SOFTIRQ);
>> +                     } else
>> +                             __napi_schedule(&queue->backlog);
>> +             }
>> +             goto enqueue;
>> +     }
>
> I still think, like Jared, this should occur at the end of the NAPI
> ->poll() run.
>

We only set the bit in remote_softirq_cpus in here.  The actual IPIs
are sent at the end net_rx_action.  I'm not exactly sure what you're
thinking on this...

> Otherwise show us numbers indicating that it makes a big difference.
> :-)
>