Re: [dpdk-dev] KNI discussion in userspace event

[Aws Ismail <aws.ismail@gmail.com>]

Hi Stephen, Ferruh,

As an end-user take on this (hence community comment) :), this ties into
the rte_eth_tap that Keith sent out and it has been acked and reviewed, So
I am trying to see the pros/cons of using this (kni pmd) vs. the tun/tap
PMD [1].

Previously, we were using Ferruh's KDP/KCP patches and those served our
purpose, but since the KDP/KCP idea has been rejected as yet another set of
out-of-tree kernel modules to maintain, it has not gotten much attention
since then.

We are hoping that tun/tap would be the way to go just because it looks
simple and easy to manage from a user app perspective.

Having said that, I am not sure what to make of this KNI PMD given
Stephen's comments. Could any one comment about the overall direction of
which solution to focus on? (tun/tap PMD or KNI pmd)?

[1]: http://dpdk.org/dev/patchwork/patch/16566/   (Keith's tun/tap PMD)

Thanks.

Aws\


On Fri, Oct 28, 2016 at 12:25 PM, Stephen Hemminger <
stephen@networkplumber.org> wrote:

> On Fri, 28 Oct 2016 15:31:50 +0100
> Ferruh Yigit <ferruh.yigit@intel.com> wrote:
>
> > Discussed alternatives were:
> > * Tun/Tap
> > This won't be as fast as KNI and performance is an issue.
>
>
> That is a myth. Both require the some number of copies.
> TUN/TAP copies is a syscall and KNI copies is a kthread.
> Actually, the KNI method is worse because it has kernel thread
> always running chewing a CPU. I.e it is pure poll mode.
>