linux-kernel - Re: [PATCH net-next] net: ps3_gelic_net: Use napi_alloc_skb() and napi_gro

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Message-ID: <aS1qciHDiLaK-c2f@horms.kernel.org>
Date: Mon, 1 Dec 2025 10:14:10 +0000
From: Simon Horman <horms@...nel.org>
To: Florian Fuchs <fuchsfl@...il.com>
Cc: Geoff Levand <geoff@...radead.org>, netdev@...r.kernel.org,
	Jakub Kicinski <kuba@...nel.org>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <chleroy@...nel.org>,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] net: ps3_gelic_net: Use napi_alloc_skb() and
 napi_gro_receive()

On Sun, Nov 30, 2025 at 08:41:55PM +0100, Florian Fuchs wrote:
> Use the napi functions napi_alloc_skb() and napi_gro_receive() instead
> of netdev_alloc_skb() and netif_receive_skb() for more efficient packet
> receiving. The switch to napi aware functions increases the RX
> throughput, reduces the occurrence of retransmissions and improves the
> resilience against SKB allocation failures.
> 
> Signed-off-by: Florian Fuchs <fuchsfl@...il.com>
> ---
> Note: This change has been tested on real hardware Sony PS3 (CECHL04 PAL),
> the patch was tested for many hours, with continuous system load, high
> network transfer load and injected failslab errors.
> 
> In my tests, the RX throughput increased up to 100% and reduced the
> occurrence of retransmissions drastically, with GRO enabled:
> 
> iperf3 before and after the commit, where PS3 (with this driver) is on
> the receiving side:
> Before: [  5]   0.00-10.00  sec   551 MBytes   462 Mbits/sec receiver
> After:  [  5]   0.00-10.00  sec  1.09 GBytes   939 Mbits/sec receiver
> 
> stats from the sending client to the PS3:
> Before: [  5]   0.00-10.00  sec   552 MBytes   463 Mbits/sec  3151 sender
> After:  [  5]   0.00-10.00  sec  1.09 GBytes   940 Mbits/sec   37  sender

Hi Florian,

Thanks for the rest results and confirming this has
been exercised on real HW.

Thinking out loud:

* I see that the napi_mode argument to gelic_descr_prepare_rx ensures
  that napi_alloc_skb() is only called from softirq context.

* I see that the driver already calls napi_complete_done() in
  it's poll callback, a pre-requisite for using napi_alloc_skb().

So as I understand things the use of the NAPI API by this patch is correct.

And this provides a nice example of the advantages of using this part
of the API.

Reviewed-by: Simon Horman <horms@...nel.org>