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Message-ID: <MN0PR12MB5953E37D081382AF52C309E2B7CEA@MN0PR12MB5953.namprd12.prod.outlook.com>
Date: Mon, 9 Oct 2023 19:41:35 +0000
From: "Pandey, Radhey Shyam" <radhey.shyam.pandey@....com>
To: Jakub Kicinski <kuba@...nel.org>
CC: "davem@...emloft.net" <davem@...emloft.net>,
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<krzysztof.kozlowski+dt@...aro.org>,
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Subject: RE: [PATCH net-next v7 3/3] net: axienet: Introduce dmaengine support
> -----Original Message-----
> From: Jakub Kicinski <kuba@...nel.org>
> Sent: Saturday, October 7, 2023 3:03 AM
> To: Pandey, Radhey Shyam <radhey.shyam.pandey@....com>
> Cc: davem@...emloft.net; edumazet@...gle.com; pabeni@...hat.com;
> robh+dt@...nel.org; krzysztof.kozlowski+dt@...aro.org;
> conor+dt@...nel.org; Simek, Michal <michal.simek@....com>;
> linux@...linux.org.uk; f.fainelli@...il.com; netdev@...r.kernel.org;
> devicetree@...r.kernel.org; linux-kernel@...r.kernel.org; linux-arm-
> kernel@...ts.infradead.org; git (AMD-Xilinx) <git@....com>
> Subject: Re: [PATCH net-next v7 3/3] net: axienet: Introduce dmaengine
> support
>
> On Fri, 6 Oct 2023 19:04:29 +0000 Pandey, Radhey Shyam wrote:
> > > > + netif_stop_queue(ndev);
> > > > + if (net_ratelimit())
> > > > + netdev_warn(ndev, "TX ring unexpectedly full\n");
> > >
> > > I don't see you stopping the queue when the ring gets full, am I not
> > > looking into the right place? Otherwise this is sort of expected to
> > > occasionally hapen
> >
> > We are calling stop_queue if TX ring is full. Is that what you meant?
> > netif_stop_queue(ndev);
>
> But somewhere else or just here after printing the warning?
There is call to netif_stop_queue(ndev) just before this netdev_warn.
I copied below for quick reference.
+ sg_len = skb_shinfo(skb)->nr_frags + 1;
+ if (!CIRC_SPACE(lp->tx_ring_head, lp->tx_ring_tail, TX_BD_NUM_MAX)) {
+ netif_stop_queue(ndev);
+ if (net_ratelimit())
+ netdev_warn(ndev, "TX ring unexpectedly full\n");
+ return NETDEV_TX_BUSY;
+ }
However, I noticed above check doesn't account for all frags - so will
modify the if check to see if available space is less than sg_len. If yes, then
stop the queue and return busy , else continue with xmit.
>
> The recommended flow is to stop the queue after enqueuing a packet
> successfully, if the remaining space is not enough to hold an skb with all frags
> populated. That avoids ever returning BUSY.
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