Subject: Re: ipsec impact on performance

From: Sowmini Varadhan <[email-masked]>
Date: Tue, 1 Dec 2015 13:37:20 -0500

On (12/01/15 10:18), Tom Herbert wrote:
> >      8.5-9.5 Gbps clear traffic, TSO disabled, so GSO, GRO is in effect
> >      3-4 Gbps clear traffic, with both TSO/GSO disabled
> >      1.8-2 Gbps for esp-null.
> 
> Are you losing checksum offload also?

I tried with both checksum offload on and off.
For the GSO case, doesnt make a huge difference to perf. 
For my patch, I disable h/w cksum offload, so that I can leverage
from the existing cksum calculations in the existing GSO code. That helps
a bit (goes from 3 Gbps -> 3.2 Gbps, but I need a 2x jump here)

> Thanks for the nice data! We could certainly implement GRO/GSO for
> esp-null to get your numbers up but I don't think that would be very
> useful to anyone. Do you have the performance numbers using real
> encryption?

I was using esp-null merely to not have the crypto itself perturb
the numbers (i.e., just focus on the s/w overhead for now), but here
are the numbers for the stock linux kernel stack
                Gbps  peak cpu util
esp-null         1.8   71%
aes-gcm-c-256    1.6   79%
aes-ccm-a-128    0.7   96%

That trend made me think that if we can get esp-null to be as close
as possible to GSO/GRO, the rest will follow closely behind.

So is my patch in the right direction? Anything obvious I am missing?
I'd like to budge that number beyond 3 Gbps :-)

--Sowmini