netdev - Re: [PATCH] taprio: Set the value of picos_per_byte before fill sched

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Date:   Sat, 1 Oct 2022 08:44:56 +0800
From:   jianghaoran <jianghaoran@...inos.cn>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     vinicius.gomes@...el.com, jhs@...atatu.com, jiri@...nulli.us,
        davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        vladimir.oltean@....com
Subject: Re: [PATCH] taprio: Set the value of picos_per_byte before fill
 sched_entry



在 2022/10/1 上午8:42, jianghaoran 写道:
> 
> 在 2022/9/30 上午10:18, Jakub Kicinski 写道:
>> On Wed, 28 Sep 2022 14:58:30 +0800 jianghaoran wrote:
>>> If the value of picos_per_byte is set after fill sched_entry,
>>> as a result, the min_duration calculated by length_to_duration is 0,
>>> and the validity of the input interval cannot be judged,
>>> too small intervals couldn't allow any packet to be transmitted.
>>
>> Meaning an invalid configuration is accepted but no packets
>> can ever be transmitted?  Could you make the user-visible
>> issue clearer?
> 
> Yes, It's possible that the user specifies an too small interval that 
> couldn't allow any packet to be transmitted.According to the following example,
> the interval is set to 9, and the network port enp5s0f0 cannot send any 
> data
> 
>>> It will appear like commit b5b73b26b3ca ("taprio:
>>> Fix allowing too small intervals") described problem.
>>> Here is a further modification of this problem.
>>>
>>> example:
>>
>> Here as well it seems worthwhile to mention what this is an example of.
>> e.g. "example configuration which will not be able to transmit packets"
>>
>>> tc qdisc replace dev enp5s0f0 parent root handle 100 taprio \
>>>                num_tc 3 \
>>>                map 2 2 1 0 2 2 2 2 2 2 2 2 2 2 2 2 \
>>>                queues 1@0 1@1 2@2 \
>>>                base-time  1528743495910289987 \
>>>                sched-entry S 01 9 \
>>>           sched-entry S 02 9 \
>>>           sched-entry S 04 9 \
>>>                clockid CLOCK_TAI
>>
>> Please add a Fixes tag pointing to the first commit where the issue was
>> present, and CC Vladimir Oltean <vladimir.oltean@....com> on the next
>> version.
>>
> Thank you for your suggestion. I will modify it as suggested