netdev - Re: Single core gets pegged on multi-core PPTP server

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Date:	Fri, 20 Jan 2012 00:55:36 +0200
From:	Emanuil Hristov <int986@...il.com>
To:	Bradley Peterson <despite@...il.com>
Cc:	paulus@...ba.org, linux-ppp@...r.kernel.org,
	netdev@...r.kernel.org, int986@...il.com
Subject: Re: Single core gets pegged on multi-core PPTP server

Hi,
try with more recent version of accel-ppp (1.5 is lastest) and newer
kernel - there
are several critical bugs in older kernels


P.S the project accel-pptp has changed its name to accel-ppp

cheers

On Fri, Jan 20, 2012 at 12:35 AM, Bradley Peterson <despite@...il.com> wrote:
> Hello,
>
> I am trying to test the capacity of a linux PPTP server, both in
> number of connections, and in packets per second.  I am using kernel
> 2.6.38.8, with the ppp, pptp, and gre modules, and accel-pptp 0.8.3.
> I have RPS, RFS, and XPS enabled on the network devices for SMP
> support.
>
> But I'm seeing one CPU get pegged out with soft interrupt, while the
> others are almost completely idle.
>
> In my current test, I'm starting 250 pptp connections from another
> server, then running iperf across each connection.  The client machine
> pegs out, sure, but I'm surprised the server pegs out a single CPU.
> With RPS, I would expect softirq's to be more balanced.
>
> Where could the bottleneck be?  Do all ppp packets need to be
> processed serially?
>
> Brad
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