Re: [PATCH: 2.6.13-15-SMP 3/3] network: concurrently runsoftirqnetwork code on SMP

[Stephen Hemminger <shemminger@linux-foundation.org>]

On Tue, 25 Sep 2007 23:36:25 +0800
"john ye" <johny@asimco.com.cn> wrote:

> Jamal,
> 
> You pointed out a key point: it's NOT acceptable if massive packet re-ordering couldn¡¯t be avoided.
> I debugged function tcp_ofo_queue in net/ipv4/tcp_input.c & monitored out_of_order_queue, found that re-ordering
> becomes unacceptable with the softirq load grows.
> 
> It's simple to avoid out-of-order packets by changing random dispatch into dispatch based on source ip address.
> e.g. cpu = iph->saddr % nr_cpus. while cpu is like a hash entry.
> Considering that BS patch is mainly used on server with many incoming connections,
> dispatch by IP should balance CPU load well.
> 
> The test is under way, it's not bad so far.
> The queue spin_lock seems not cost much.
> 
> Below is the bcpp beautified module code. Last time code mess is caused by outlook express which killed tabs.
> 
> Thanks.
> 
> John Ye

There is a standard hash called RSS, that many drivers support because it is
used by other operating systems.