Subject: Re: ipsec impact on performance

From: Sowmini Varadhan <[email-masked]>
Date: Wed, 2 Dec 2015 08:25:11 -0500

On (12/02/15 12:41), David Laight wrote:
> 
> Also what/how are you measuring cpu use.
> I'm not sure anything on Linux gives you a truly accurate value
> when processes are running for very short periods.

I was using mpstat, while running iperf. Should I be using
something else? or running it for longer intervals?

but I hope we are not doomed at 1 Gbps, or else security itself would
come at a very unattractive cost. Anyway, even aside from crypto.
we need to have some way to add TCP options (that depend on the 
contents of the tcp header) etc post-GSO, in the interest of not 
ossifying the stack.

> On an SMP system you also get big effects when work is switched
> between cpus. I've got some tests that run a lot faster if I
> put all but one of the cpus into a busy-loop in userspace
> (eg: while :; do :; done)!

yes Rick Jones also pointed the same thing to me, and one of the
things I was going to try out later today is to instrument the
effects of pinning irqs and iperf threads to a specific cpu.

--Sowmini