Re: Linux stack performance drop (TCP and UDP) in 3.10 kernel in routed scenario

[Suprasad Mutalik Desai <suprasad.desai@gmail.com>]

Hi David,

On Thu, Jun 5, 2014 at 12:48 AM, David Miller <davem@davemloft.net> wrote:
> From: Suprasad Mutalik Desai <suprasad.desai@gmail.com>
> Date: Wed, 4 Jun 2014 14:34:10 +0530
>
>> I guess plain routing scenario was NOT thought through while removing
>> the routing cache code.
>
> It is exactly the scenerio that was considered.
>
> The routing cache was susceptible to trivial denial of service
> attacks, it therefore had to be removed.
>
> It also scaled poorly with large numbers of active flows.

Based on your and Eric's explanation , i clearly understand the
purpose of removing route cache.

But as there was no alternative proposed after removing route cache
mechanism, this is causing a side effect of low throughput in an
embedded router scenario with limited cache and memory resources. With
a limited cache in an embedded router environment checking the routing
table for the dst for every packet (routed scenario) is a heavy
operation which can lead to poor stack  performance.

So, I request you to please suggest on how to address this topic w.r.t
embedded devices ( routers) which has limited memory resources ?

Thanks and Regards,
Suprasad.