Re: [PATCH v2 net-next] softirq: reduce latencies

Joe Perches
2013-01-04T08:15:52Z

On Thu, 2013-01-03 at 23:49 -0800, Eric Dumazet wrote:
> In various network workloads, __do_softirq() latencies can be up
> to 20 ms if HZ=1000, and 200 ms if HZ=100.
> This patch changes the fallback to ksoftirqd condition to :
> - A time limit of 2 ms.

[]
> diff --git a/kernel/softirq.c b/kernel/softirq.c
[]
> +#define MAX_SOFTIRQ_TIME max(1, (2*HZ/1000))

And if HZ is 10000?

> asmlinkage void __do_softirq(void)
> {
[]
> + unsigned long end = jiffies + MAX_SOFTIRQ_TIME;

Perhaps MAX_SOFTIRQ_TIME should be

#define MAX_SOFTIRQ_TIME msecs_to_jiffies(2)

though it would be nicer if it were a compile time constant.