netdev - Re: [RFC PATCH net-next v6 4/4] netvsc: refactor notifier/event handling code to use the bypass framework

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Date:   Tue, 10 Apr 2018 14:26:08 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Sridhar Samudrala <sridhar.samudrala@...el.com>
Cc:     mst@...hat.com, davem@...emloft.net, netdev@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        virtio-dev@...ts.oasis-open.org, jesse.brandeburg@...el.com,
        alexander.h.duyck@...el.com, kubakici@...pl, jasowang@...hat.com,
        loseweigh@...il.com, jiri@...nulli.us
Subject: Re: [RFC PATCH net-next v6 4/4] netvsc: refactor notifier/event
 handling code to use the bypass framework

On Tue, 10 Apr 2018 11:59:50 -0700
Sridhar Samudrala <sridhar.samudrala@...el.com> wrote:

> Use the registration/notification framework supported by the generic
> bypass infrastructure.
> 
> Signed-off-by: Sridhar Samudrala <sridhar.samudrala@...el.com>
> ---

Thanks for doing this.  Your current version has couple show stopper
issues.

First, the slave device is instantly taking over the slave.
This doesn't allow udev/systemd to do its device rename of the slave
device. Netvsc uses a delayed work to workaround this.

Secondly, the select queue needs to call queue selection in VF.
The bonding/teaming logic doesn't work well for UDP flows.
Commit b3bf5666a510 ("hv_netvsc: defer queue selection to VF")
fixed this performance problem.

Lastly, more indirection is bad in current climate.

I am not completely adverse to this but it needs to be fast, simple
and completely transparent.