Re: [PATCH net-next v3 2/5] net: add sysfs attribute to control napi threaded mode

[Wei Wang <weiwan@google.com>]

On Wed, Nov 18, 2020 at 12:36 PM Randy Dunlap <rdunlap@infradead.org> wrote:
>
> On 11/18/20 11:10 AM, Wei Wang wrote:
> > From: Paolo Abeni <pabeni@redhat.com>
> >
> > this patch adds a new sysfs attribute to the network
> > device class. Said attribute is a bitmask that allows controlling
> > the threaded mode for all the napi instances of the given
> > network device.
> >
> > The threaded mode can be switched only if related network device
> > is down.
> >
> > Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> > Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
> > Signed-off-by: Wei Wang <weiwan@google.com>
> > Reviewed-by: Eric Dumazet <edumazet@google.com>
>
> Hi,
>
> Could someone describe the bitmask (is it a bit per instance of the
> network device?).
> And how to use the sysfs interface, please?
>

It is 1 bit per napi. Depending on the driver implementation, 1 napi
could correspond to 1 tx queue, or 1 rx queue, or 1 pair of tx/rx
queues.
To set bits in the bit mask, you could do:
echo 0-14 > /sys/class/net/<dev>/threaded
to set consecutive bits.
or:
echo 0,2,4,6,8 >  /sys/class/net/<dev>/threaded
to set individual bits.

To clear the bit mask, you could do:
echo > /sys/class/net/<dev>/threaded

> > ---
> >  net/core/net-sysfs.c | 103 +++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 103 insertions(+)
> >
> > diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
> > index 94fff0700bdd..df8dd25e5e4b 100644
> > --- a/net/core/net-sysfs.c
> > +++ b/net/core/net-sysfs.c
>
>
> thanks.
> --
> ~Randy
>