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

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Message-ID: <CAJMXqXZV+tGPi5_d-ndeLYfx-yV6WiyDRBaqMcs0dYNTKfZHrw@mail.gmail.com>
Date:	Thu, 5 Jun 2014 07:47:48 +0530
From:	Suprasad Mutalik Desai <suprasad.desai@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	davem@...emloft.ne
Subject: Re: Linux stack performance drop (TCP and UDP) in 3.10 kernel in
 routed scenario

Hi David,

On Thu, Jun 5, 2014 at 12:48 AM, David Miller <davem@...emloft.net> wrote:
> From: Suprasad Mutalik Desai <suprasad.desai@...il.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.
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