netdev - Re: [PATCH net-next 4/5] eth: fbnic: add PCIe hardware statistics

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Message-ID: <1ed2ba1e-b87f-4738-9d72-da7c5a7180e2@lunn.ch>
Date: Sun, 17 Nov 2024 21:19:00 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Jakub Kicinski <kuba@...nel.org>
Cc: davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
	pabeni@...hat.com, alexanderduyck@...com,
	Sanman Pradhan <sanman.p211993@...il.com>
Subject: Re: [PATCH net-next 4/5] eth: fbnic: add PCIe hardware statistics

> +/* PUL User Registers*/
> +#define FBNIC_PUL_USER_OB_RD_TLP_CNT_31_0 \
> +					0x3106e		/* 0xc41b8 */

Is there a comment somewhere which explains what these comments mean?
Otherwise they appear to be useless magic numbers.

> +static void fbnic_hw_stat_rst64(struct fbnic_dev *fbd, u32 reg, s32 offset,
> +				struct fbnic_stat_counter *stat)
> +{
> +	/* Record initial counter values and compute deltas from there to ensure
> +	 * stats start at 0 after reboot/reset. This avoids exposing absolute
> +	 * hardware counter values to userspace.
> +	 */
> +	stat->u.old_reg_value_64 = fbnic_stat_rd64(fbd, reg, offset);

I don't know how you use these stats, but now they are in debugfs, do
they actually need to be 0 after reboot/reset? For most debugging
performance issues with statistics, i want to know how much a counter
goes up per second, so userspace will be reading the values twice with
a sleep, and doing a subtractions anyway. So why not make the kernel
code simpler?

     Andrew