netdev - Re: Re: [PATCH v1 net] net/sched: taprio: enforce minimum value for picos_per

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Message-ID: <20250725052150.48532-1-takamitz@amazon.co.jp>
Date: Fri, 25 Jul 2025 14:21:50 +0900
From: Takamitsu Iwai <takamitz@...zon.co.jp>
To: <vinicius.gomes@...el.com>
CC: <davem@...emloft.net>, <edumazet@...gle.com>, <horms@...nel.org>,
	<jhs@...atatu.com>, <jiri@...nulli.us>, <kuba@...nel.org>,
	<kuniyu@...gle.com>, <netdev@...r.kernel.org>, <olteanv@...il.com>,
	<pabeni@...hat.com>, <syzbot+398e1ee4ca2cac05fddb@...kaller.appspotmail.com>,
	<takamitz@...zon.co.jp>, <takamitz@...zon.com>, <xiyou.wangcong@...il.com>
Subject: Re: Re: [PATCH v1 net] net/sched: taprio: enforce minimum value for picos_per_byte

On 2025/07/25, 3:58, "Vinicius Costa Gomes" <vinicius.gomes@...el.com <mailto:vinicius.gomes@...el.com>> wrote:
> Takamitsu Iwai <takamitz@...zon.co.jp <mailto:takamitz@...zon.co.jp>> writes:
> > @@ -1299,7 +1305,7 @@ static void taprio_set_picos_per_byte(struct net_device *dev,
> > speed = ecmd.base.speed;
> >
> > skip:
> > - picos_per_byte = (USEC_PER_SEC * 8) / speed;
> > + picos_per_byte = max((USEC_PER_SEC * 8) / speed,
> > TAPRIO_PICOS_PER_BYTE_MIN);
> 
> 
> Thinking if it's worth displaying an error to the user here? something
> like "Linkspeed %d is greater than what can be tracked, schedule may be
> inacurate". I am worried that at this point, taprio won't be able to
> obey the configured schedule and the user should know about that.
> 
> 
> If we see people complaining about it in the real world, we can change
> the units, or do something else.

Thank you for your feedback on this patch.

I agree with adding message about this here. I'll revise the patch to add 
a pr_warn() message when the calculated picos_per_byte would be below the
minimum threshold.


Thanks.
Takamitsu