netdev - Re: [PATCH v2] RPS: Sparse connection optimizations

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Date:	Fri, 04 May 2012 09:47:49 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Deng-Cheng Zhu <dczhu@...s.com>
Cc:	Tom Herbert <therbert@...gle.com>, davem@...emloft.net,
	netdev@...r.kernel.org
Subject: Re: [PATCH v2] RPS: Sparse connection optimizations - v2

On Fri, 2012-05-04 at 12:25 +0800, Deng-Cheng Zhu wrote:
> On 05/04/2012 11:22 AM, Tom Herbert wrote:
> >> +struct cpu_flow {
> >> +       struct net_device *dev;
> >> +       u32 rxhash;
> >> +       unsigned long ts;
> >> +};
> >
> > This seems like overkill, we already have the rps_flow_table and this
> > used in accelerated RFS so the device can also take advantage of
> > steering.
> 
> I think the mechanisms of rps_dev_flow_table and cpu_flow (in this
> patch) are different: The former works along with rps_sock_flow_table
> whose CPU info is based on recvmsg by the application. But for the tests
> like what I did, there's no application involved.
> 
> 
> Deng-Cheng

I really suggest you speak with MIPS arch maintainers about these IRQ
being all serviced by CPU0.

Adding tweaks in network stack to lower the impact of this huge problem
is a no go.



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