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From:   Shinas Rasheed <srasheed@marvell.com>
To:     Jakub Kicinski <kuba@kernel.org>,
        Eric Dumazet <edumazet@google.com>
CC:     "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Haseeb Gani <hgani@marvell.com>,
        Vimlesh Kumar <vimleshk@marvell.com>,
        "egallen@redhat.com" <egallen@redhat.com>,
        "mschmidt@redhat.com" <mschmidt@redhat.com>,
        "pabeni@redhat.com" <pabeni@redhat.com>,
        "horms@kernel.org" <horms@kernel.org>,
        "davem@davemloft.net" <davem@davemloft.net>,
        "wizhao@redhat.com" <wizhao@redhat.com>,
        "konguyen@redhat.com" <konguyen@redhat.com>,
        Veerasenareddy Burru <vburru@marvell.com>,
        Sathesh B Edara <sedara@marvell.com>
Subject: RE: [EXT] Re: [PATCH net-next v2 3/4] octeon_ep: implement xmit_more
 in transmit
Thread-Topic: [EXT] Re: [PATCH net-next v2 3/4] octeon_ep: implement xmit_more
 in transmit
Thread-Index: AQHaBomdyCzd/AB+BUOLdgCH/VlJFbBZpWyAgAIItnKAAHrBAIABV/rw
Date:   Fri, 27 Oct 2023 11:25:16 +0000
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> -----Original Message-----
> From: Jakub Kicinski <kuba@kernel.org>
> Sent: Thursday, October 26, 2023 8:15 PM
> To: Shinas Rasheed <srasheed@marvell.com>
> Cc: netdev@vger.kernel.org; linux-kernel@vger.kernel.org; Haseeb Gani
> <hgani@marvell.com>; Vimlesh Kumar <vimleshk@marvell.com>;
> egallen@redhat.com; mschmidt@redhat.com; pabeni@redhat.com;
> horms@kernel.org; davem@davemloft.net; wizhao@redhat.com;
> konguyen@redhat.com; Veerasenareddy Burru <vburru@marvell.com>;
> Sathesh B Edara <sedara@marvell.com>; Eric Dumazet
> <edumazet@google.com>
> Subject: Re: [EXT] Re: [PATCH net-next v2 3/4] octeon_ep: implement
> xmit_more in transmit
>=20
> On Thu, 26 Oct 2023 07:57:54 +0000 Shinas Rasheed wrote:
> > >The recommended way of implementing 'driver flow control'
> > is to stop the queue once next packet may not fit, and then use
> > netif_xmit_stopped() when deciding whether we need to flush or we can
> > trust xmit_more. see
> > https://urldefense.proofpoint.com/v2/url?u=3Dhttps-
> 3A__www.kernel.org_doc_html_next_networking_driver.html-23transmit-
> 2Dpath-2Dguidelines&d=3DDwICAg&c=3DnKjWec2b6R0mOyPaz7xtfQ&r=3D1OxLD4y-
> oxrlgQ1rjXgWtmLz1pnaDjD96sDq-
> cKUwK4&m=3DFyJHTb5Z2u9DTFSYPU38S5kPcP5KvwGWzY-
> DPcqOl1gdnm7ToZhTFpyvhLMqh1hd&s=3DdBMmwfWKAi0UH3nrz7j9kYnAodDj
> uN3LZ5tC2aL_Prs&e=3D
> >
> > >> In the skeleton code above, as I understand each tx desc holds a skb=
 frag
> and hence there can be possibility of receiving a full-sized skb, stoppin=
g the
> queue but on receiving another normal skb we should observe our queue to
> be stopped. This doesn't arise in our case as even if the skb is full-siz=
ed, it will
> only use a single tx descriptor so we can be sure if queue has been stopp=
ed,
> the write index will only be updated once posted (and read) tx descriptor=
s
> are processed in napi context and queues awoken.
> >
> > Please correct me if I'm wrong anywhere (sorry if so) to further my
> understanding, and again thanks for your time!
>=20
> Could you please do some training on how to use normal / mailing list
> style email at Marvell? Multiple people from Marvell can't quote
> replies correctly, it makes it hard to have a conversation and help
> y'all.
Hi Jacub, apologizing for format errors on my part, will try to rectify in =
coming mails. Sorry again.


> -----Original Message-----
> From: Eric Dumazet <edumazet@google.com>
> Sent: Thursday, October 26, 2023 1:59 PM
> To: Shinas Rasheed <srasheed@marvell.com>
> Cc: Jakub Kicinski <kuba@kernel.org>; netdev@vger.kernel.org; linux-
> kernel@vger.kernel.org; Haseeb Gani <hgani@marvell.com>; Vimlesh Kumar
> <vimleshk@marvell.com>; egallen@redhat.com; mschmidt@redhat.com;
> pabeni@redhat.com; horms@kernel.org; davem@davemloft.net;
> wizhao@redhat.com; konguyen@redhat.com; Veerasenareddy Burru
> <vburru@marvell.com>; Sathesh B Edara <sedara@marvell.com>
> Subject: Re: [EXT] Re: [PATCH net-next v2 3/4] octeon_ep: implement
> xmit_more in transmit
>=20
> Fact that octep_start_xmit() can return NETDEV_TX_BUSY is very suspicious=
.
>=20
> I do not think a driver can implement xmit_more and keep
> NETDEV_TX_BUSY at the same time.
>=20
> Please make sure to remove NETDEV_TX_BUSY first, by stopping the queue
> earlier.

Hi Eric, I think I understand your point and shall submit an updated patch.=
 Thanks your time!