linux-kernel - RE: [PATCH net] net: fec: tx processing does not call XDP APIs if budget is 0

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Message-ID: <AM5PR04MB313925B5EF7F4A1ABFBFFB5A8801A@AM5PR04MB3139.eurprd04.prod.outlook.com>
Date:   Thu, 27 Jul 2023 05:32:51 +0000
From:   Wei Fang <wei.fang@....com>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     Alexander Duyck <alexander.duyck@...il.com>,
        dl-linux-imx <linux-imx@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        Shenwei Wang <shenwei.wang@....com>,
        Clark Wang <xiaoning.wang@....com>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH net] net: fec: tx processing does not call XDP APIs if
 budget is 0

> On Thu, 27 Jul 2023 02:08:32 +0000 Wei Fang wrote:
> > > Actually after talking with Jakub a bit more there is an issue here,
> > > but not freeing the frames isn't the solution. We likely need to
> > > just fix the page pool code so that it doesn't attempt to recycle
> > > the frames if operating in IRQ context.
> > >
> > > The way this is dealt with for skbs is that we queue skbs if we are
> > > in IRQ context so that it can be deferred to be freed by the
> > > net_tx_action. We likely need to look at doing something similar for
> > > page_pool pages or XDP frames.
> > >
> > After reading your discussion with Jakub, I understand this issue a bit more.
> > But we are not sure when this issue will be fixed in page pool,
> > currently we can only tolerate a delay in sending of a netpoll
> > message. So I think this patch is necessary, and I will refine it in
> > the future when the page pool has fixed the issue. In addition, as you
> > mentioned before, napi_consume_skb should be used to instead of
> dev_kfree_skb_any, so I will improve this patch in version 2.
> 
> I think so too, since the patch can only help, you already wrote it and it won't
> be extra backporting work since the code is only present in
> 6.5 - I think it's worth applying. And we can refine things as page pool
> limitations get listed (the napi_consume_skb() is net-next material, anyway).
Okay, thank you. :)