From: "Michael S. Tsirkin" <mst@redhat•com>
To: Alvaro Karsz <alvaro.karsz@solid-run•com>
Cc: Jason Wang <jasowang@redhat•com>,
Jakub Kicinski <kuba@kernel•org>, netdev <netdev@vger•kernel.org>,
"David S. Miller" <davem@davemloft•net>,
Eric Dumazet <edumazet@google•com>,
Paolo Abeni <pabeni@redhat•com>
Subject: Re: [PATCH net-next v4] net: virtio_net: notifications coalescing support
Date: Wed, 20 Jul 2022 03:15:27 -0400 [thread overview]
Message-ID: <20220720031436-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <CAJs=3_DHW6qwjjx3ZBH2SVC0kaKviSrHHG+Hsh8-VxAbRNdP7A@mail.gmail.com>
On Wed, Jul 20, 2022 at 10:07:11AM +0300, Alvaro Karsz wrote:
> > Hmm. we currently (ab)use tx_max_coalesced_frames values 0 and 1 to mean tx
> napi on/off.
> > However I am not sure we should treat any value != 1 as napi on.
> >
> > I don't really have good ideas - I think abusing coalescing might
> > have been a mistake. But now that we are there, I feel we need
> > a way for userspace to at least be able to figure out whether
> > setting coalescing to 0 will have nasty side effects.
>
>
> So, how can I proceed from here?
> Maybe we don't need to use tx napi when this feature is negotiated (like Jakub
> suggested in prev. versions)?
> It makes sense, since the number of TX notifications can be reduced by setting
> tx_usecs/tx_max_packets with ethtool.
Hmm Jason had some ideas about extensions in mind when he
coded the current UAPI, let's see if he has ideas.
I'll ruminate on compatibility a bit too.
> > It's also a bit of a spec defect that it does not document corner cases
> > like what do 0 values do, are they different from 1? or what are max values.
> > Not too late to fix?
>
>
> I think that some of the corner cases can be understood from the coalescing
> values.
> For example:
> if rx_usecs=0 we should wait for 0 usecs, meaning that we should send a
> notification immediately.
> But if rx_usecs=1 we should wait for 1 usec.
> The case with max_packets is a little bit unclear for the values 0/1, and it
> seems that in both cases we should send a notification immediately after
> receiving/sending a packet.
>
>
> > So the spec says
> > Device supports notifications coalescing.
> >
> > which makes more sense - there's not a lot guest needs to do here.
>
>
> Noted.
>
> > parameters?
>
>
> I'll change it to "settings".
>
> > why with dash here? And why not just put the comments near the fields
> > themselves?
>
>
> Noted.
next prev parent reply other threads:[~2022-07-20 7:15 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-18 9:11 [PATCH net-next v4] net: virtio_net: notifications coalescing support Alvaro Karsz
2022-07-19 7:03 ` Jason Wang
2022-07-19 7:08 ` Alvaro Karsz
2022-07-19 7:12 ` Jason Wang
2022-07-19 7:18 ` Alvaro Karsz
2022-07-19 7:31 ` Jason Wang
2022-07-20 0:26 ` Jakub Kicinski
2022-07-20 6:45 ` Michael S. Tsirkin
2022-07-20 7:02 ` Jason Wang
2022-07-20 7:05 ` Michael S. Tsirkin
2022-07-20 7:15 ` Jason Wang
2022-07-20 9:05 ` Michael S. Tsirkin
[not found] ` <CAJs=3_DHW6qwjjx3ZBH2SVC0kaKviSrHHG+Hsh8-VxAbRNdP7A@mail.gmail.com>
2022-07-20 7:15 ` Michael S. Tsirkin [this message]
2022-07-20 7:42 ` Jason Wang
2022-07-20 7:45 ` Jason Wang
2022-07-20 7:56 ` Alvaro Karsz
2022-07-20 8:28 ` Jason Wang
2022-07-20 9:09 ` Michael S. Tsirkin
2022-07-20 6:28 ` Michael S. Tsirkin
2022-07-20 8:52 ` Jason Wang
2022-08-09 19:11 ` Michael S. Tsirkin
2022-08-09 19:14 ` Michael S. Tsirkin
2022-08-29 8:46 ` Xuan Zhuo
2022-08-29 9:14 ` Alvaro Karsz
2022-08-29 9:18 ` Xuan Zhuo
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