On Thu, Jan 23, 2025 at 10:47 AM Joe Damato <jdamato@xxxxxxxxxx> wrote:
>
> On Thu, Jan 23, 2025 at 10:40:43AM +0800, Jason Wang wrote:
> > On Thu, Jan 23, 2025 at 1:41 AM Joe Damato <jdamato@xxxxxxxxxx> wrote:
> > >
> > > On Wed, Jan 22, 2025 at 02:12:46PM +0800, Jason Wang wrote:
> > > > On Wed, Jan 22, 2025 at 3:11 AM Joe Damato <jdamato@xxxxxxxxxx> wrote:
> > > > >
> > > > > Slight refactor to prepare the code for NAPI to queue mapping. No
> > > > > functional changes.
> > > > >
> > > > > Signed-off-by: Joe Damato <jdamato@xxxxxxxxxx>
> > > > > Reviewed-by: Gerhard Engleder <gerhard@xxxxxxxxxxxxxxxxxxxxx>
> > > > > Tested-by: Lei Yang <leiyang@xxxxxxxxxx>
> > > > > ---
> > > > > v2:
> > > > > - Previously patch 1 in the v1.
> > > > > - Added Reviewed-by and Tested-by tags to commit message. No
> > > > > functional changes.
> > > > >
> > > > > drivers/net/virtio_net.c | 10 ++++++++--
> > > > > 1 file changed, 8 insertions(+), 2 deletions(-)
> > > > >
> > > > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > > > > index 7646ddd9bef7..cff18c66b54a 100644
> > > > > --- a/drivers/net/virtio_net.c
> > > > > +++ b/drivers/net/virtio_net.c
> > > > > @@ -2789,7 +2789,8 @@ static void skb_recv_done(struct virtqueue *rvq)
> > > > > virtqueue_napi_schedule(&rq->napi, rvq);
> > > > > }
> > > > >
> > > > > -static void virtnet_napi_enable(struct virtqueue *vq, struct napi_struct *napi)
> > > > > +static void virtnet_napi_do_enable(struct virtqueue *vq,
> > > > > + struct napi_struct *napi)
> > > > > {
> > > > > napi_enable(napi);
> > > >
> > > > Nit: it might be better to not have this helper to avoid a misuse of
> > > > this function directly.
> > >
> > > Sorry, I'm probably missing something here.
> > >
> > > Both virtnet_napi_enable and virtnet_napi_tx_enable need the logic
> > > in virtnet_napi_do_enable.
> > >
> > > Are you suggesting that I remove virtnet_napi_do_enable and repeat
> > > the block of code in there twice (in virtnet_napi_enable and
> > > virtnet_napi_tx_enable)?
> >
> > I think I miss something here, it looks like virtnet_napi_tx_enable()
> > calls virtnet_napi_do_enable() directly.
> >
> > I would like to know why we don't call netif_queue_set_napi() for TX NAPI here?
>
> Please see both the cover letter and the commit message of the next
> commit which addresses this question.
>
> TX-only NAPIs do not have NAPI IDs so there is nothing to map.
Interesting, but I have more questions
1) why need a driver to know the NAPI implementation like this?
2) does NAPI know (or why it needs to know) whether or not it's a TX
or not? I only see the following code in napi_hash_add():
static void napi_hash_add(struct napi_struct *napi)
{
unsigned long flags;
if (test_bit(NAPI_STATE_NO_BUSY_POLL, &napi->state))
return;
...
__napi_hash_add_with_id(napi, napi_gen_id);
spin_unlock_irqrestore(&napi_hash_lock, flags);
}
It seems it only matters with NAPI_STATE_NO_BUSY_POLL.
And if NAPI knows everything, should it be better to just do the
linking in napi_enable/disable() instead of letting each driver do it
by itself?
Thanks
>
