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Subject: Re: [net-next RFC v3 6/7] net: ravb: Use NAPI threaded mode on 1-core
 CPUs with GbEth IP
To: Paul Barker <paul.barker.ct@bp.renesas.com>, "David S. Miller"
	<davem@davemloft.net>, Eric Dumazet <edumazet@google.com>, Jakub Kicinski
	<kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>
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	Geert Uytterhoeven <geert+renesas@glider.be>, <netdev@vger.kernel.org>,
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References: <20240415094804.8016-1-paul.barker.ct@bp.renesas.com>
 <20240415094804.8016-7-paul.barker.ct@bp.renesas.com>
From: Sergey Shtylyov <s.shtylyov@omp.ru>
Organization: Open Mobile Platform
Message-ID: <66667ef2-2e0b-3c31-66ad-d6d6514919c7@omp.ru>
Date: Fri, 19 Apr 2024 23:32:16 +0300
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On 4/15/24 12:48 PM, Paul Barker wrote:

> NAPI Threaded mode (along with the previously enabled SW IRQ Coalescing)
> is required to improve network stack performance for single core SoCs
> using the GbEth IP (currently the RZ/G2L SoC family and the RZ/G3S SoC).
> 
> This patch gives the following improvements during testing with iperf3.
> 
>   * RZ/G2UL:
>     * TCP TX: +32% bandwidth (638Mbps -> 841Mbps)
>     * TXP RX: +8.8% bandwidth (667Mbps -> 726Mbps)
>     * UDP RX: +104% bandwidth (53Mbps -> 108Mbps)
> 
>   * RZ/G3S:
>     * TCP TX: 29% bandwidth (529Mbps -> 681Mbps)
>     * UDP RX: +1290% bandwidth (6.46Mbps -> 90Mbps)
> 
>   * RZ/Five:
>     * UDP RX: Test no longer crashes (0 -> 20 Mbps)
> 
> This patch gives the following reductions in performance in the same
> testing:
> 
>   * RZ/G2UL:
>     * UDP TX: -7.5% bandwidth (594Mbps -> 549Mbps)
> 
>   * RZ/G3S:
>     * UDP TX: -5% bandwidth (625Mbps -> 594Mbps)
> 
> These losses are considered acceptable given the benefits shown above.
> If UDP TX bandwidth must be maximised for a particular use case, NAPI
> threaded mode can be disabled at runtime via sysfs writes.
> 
> The improvement of UDP RX bandwidth for the single core SoCs (RZ/G2UL &
> RZ/G3S) is particularly critical.
> 
> Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>

Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>

[...]

MBR, Sergey