netdev - Re: [PATCH net-next V2] eth: fbnic: Add ethtool support for IRQ coalescing

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Message-ID: <bd76941d-a6fa-483d-8f91-a5d699b6b945@lunn.ch>
Date: Fri, 14 Feb 2025 13:55:56 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Mohsin Bashir <mohsin.bashr@...il.com>
Cc: netdev@...r.kernel.org, alexanderduyck@...com, kuba@...nel.org,
	andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com,
	pabeni@...hat.com, linux@...linux.org.uk, sanman.p211993@...il.com,
	vadim.fedorenko@...ux.dev, suhui@...china.com, horms@...nel.org,
	sdf@...ichev.me, jdamato@...tly.com, brett.creeley@....com,
	przemyslaw.kitszel@...el.com, colin.i.king@...il.com,
	kernel-team@...a.com
Subject: Re: [PATCH net-next V2] eth: fbnic: Add ethtool support for IRQ
 coalescing

On Thu, Feb 13, 2025 at 07:50:37PM -0800, Mohsin Bashir wrote:
> Add ethtool support to configure the IRQ coalescing behavior. Support
> separate timers for Rx and Tx for time based coalescing. For frame based
> configuration, currently we only support the Rx side.
> 
> The hardware allows configuration of descriptor count instead of frame
> count requiring conversion between the two. We assume 2 descriptors
> per frame, one for the metadata and one for the data segment.
> 
> When rx-frames are not configured, we set the RX descriptor count to
> half the ring size as a fail safe.
> 
> Default configuration:
> ethtool -c eth0 | grep -E "rx-usecs:|tx-usecs:|rx-frames:"
> rx-usecs:       30
> rx-frames:      0
> tx-usecs:       35
> 
> IRQ rate test:
> With single iperf flow we monitor IRQ rate while changing the tx-usesc and
> rx-usecs to high and low values.
> 
> ethtool -C eth0 rx-frames 8192 rx-usecs 150 tx-usecs 150
> irq/sec   13k
> irq/sec   14k
> irq/sec   14k
> 
> ethtool -C eth0 rx-frames 8192 rx-usecs 10 tx-usecs 10
> irq/sec  27k
> irq/sec  28k
> irq/sec  28k
> 
> Validating the use of extack:
> ethtool -C eth0 rx-frames 16384
> netlink error: fbnic: rx_frames is above device max
> netlink error: Invalid argument

Nice, thanks.

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew