linux-kernel - Re: [PATCH v1 net-next] net: lan743x: configure interrupt moderation timers based on speed

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Message-ID: <42768d74fc73cd3409f9cdd5c5c872747c2d7216.camel@microchip.com>
Date: Tue, 6 May 2025 04:02:30 +0000
From: <Thangaraj.S@...rochip.com>
To: <andrew@...n.ch>
CC: <Bryan.Whitehead@...rochip.com>, <andrew+netdev@...n.ch>,
	<davem@...emloft.net>, <linux-kernel@...r.kernel.org>, <pabeni@...hat.com>,
	<kuba@...nel.org>, <edumazet@...gle.com>, <netdev@...r.kernel.org>,
	<UNGLinuxDriver@...rochip.com>
Subject: Re: [PATCH v1 net-next] net: lan743x: configure interrupt moderation
 timers based on speed

Hi Andrew,
Thanks for reviewing the patch,

On Mon, 2025-05-05 at 14:15 +0200, Andrew Lunn wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you
> know the content is safe
> 
> On Mon, May 05, 2025 at 12:59:43PM +0530, Thangaraj Samynathan wrote:
> > Configures the interrupt moderation timer value to 64us for 2.5G,
> > 150us for 1G, 330us for 10/100M. Earlier this was 400us for all
> > speeds. This improvess UDP TX and Bidirectional performance to
> > 2.3Gbps from 1.4Gbps in 2.5G. These values are derived after
> > experimenting with different values.
> 
> It would be good to also implement:
> 
>        ethtool -c|--show-coalesce devname
> 
>        ethtool -C|--coalesce devname [adaptive-rx on|off] [adaptive-
> tx on|off]
>               [rx-usecs N] [rx-frames N] [rx-usecs-irq N] [rx-frames-
> irq N]
>               [tx-usecs N] [tx-frames N] [tx-usecs-irq N] [tx-frames-
> irq N]
>               [stats-block-usecs N] [pkt-rate-low N] [rx-usecs-low N]
>               [rx-frames-low N] [tx-usecs-low N] [tx-frames-low N]
>               [pkt-rate-high N] [rx-usecs-high N] [rx-frames-high N]
>               [tx-usecs-high N] [tx-frames-high N] [sample-interval
> N]
>               [cqe-mode-rx on|off] [cqe-mode-tx on|off] [tx-aggr-max-
> bytes N]
>               [tx-aggr-max-frames N] [tx-aggr-time-usecs N]
> 
> so the user can configure it. Sometimes lower power is more important
> than high speed.
> 
>         Andrew

We've tuned the interrupt moderation values based on testing to improve
performance. For now, we’ll keep these fixed values optimized for
performance across all speeds. That said, we agree that adding ethtool
-c/-C support would provide valuable flexibility for users to balance
power and performance, and we’ll consider implementing that in a future
update.