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

["Samudrala, Sridhar" <sridhar.samudrala@intel.com>]

On 4/10/2018 2:26 PM, Stephen Hemminger wrote:
> On Tue, 10 Apr 2018 11:59:50 -0700
> Sridhar Samudrala <sridhar.samudrala@intel.com> wrote:
>
> > Use the registration/notification framework supported by the generic
> > bypass infrastructure.
> >
> > Signed-off-by: Sridhar Samudrala <sridhar.samudrala@intel.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.

OK. I guess you are referring to the dev_set_mtu() and dev_open() calls that are
made in bypass_slave_register() and you want to defer them to be done after
a delay.  I could avoid these calls in case of netvsc based on bypass_ops.


> 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.

netvsc should not be using bypass_select_queue() as  that ndo op gets used
only with 3-netdev model.
Anyway, will look into updating bypass_select_queue() based on your fix.

> 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.

Not sure we can avoid this indirection if we want to commonize the code,  but use
different models for virtio-net and netvsc.

On the other hand, these patches avoid calls to get_netvsc_bymac() and
get_netvsc_by_ref() that go through all the devices for all the netdev events.
netvsc lookups should be much faster.

Thanks
Sridhar