netdev - Re: [PATCH iproute2-next] tc/htb: Hierarchical QoS hardware offload

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Date:   Tue, 2 Feb 2021 08:32:06 -0700
From:   David Ahern <dsahern@...il.com>
To:     Maxim Mikityanskiy <maximmi@...dia.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>
Cc:     Saeed Mahameed <saeedm@...dia.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Tariq Toukan <tariqt@...dia.com>,
        Yossi Kuperman <yossiku@...dia.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        netdev@...r.kernel.org, Maxim Mikityanskiy <maximmi@...lanox.com>
Subject: Re: [PATCH iproute2-next] tc/htb: Hierarchical QoS hardware offload

On 2/2/21 4:46 AM, Maxim Mikityanskiy wrote:
> On 2021-01-29 18:05, David Ahern wrote:
>> On 12/15/20 12:42 AM, Maxim Mikityanskiy wrote:
>>> This commit adds support for configuring HTB in offload mode. HTB
>>> offload eliminates the single qdisc lock in the datapath and offloads
>>> the algorithm to the NIC. The new 'offload' parameter is added to
>>> enable this mode:
>>>
>>>      # tc qdisc replace dev eth0 root handle 1: htb offload
>>>
>>> Classes are created as usual, but filters should be moved to clsact for
>>> lock-free classification (filters attached to HTB itself are not
>>> supported in the offload mode):
>>>
>>>      # tc filter add dev eth0 egress protocol ip flower dst_port 80
>>>      action skbedit priority 1:10
>>
>> please add the dump in both stdout and json here.
> 
> Do you mean to add example output to the commit message?

yes.

>>>   diff --git a/tc/q_htb.c b/tc/q_htb.c
>>> index c609e974..fd11dad6 100644
>>> --- a/tc/q_htb.c
>>> +++ b/tc/q_htb.c
>>> @@ -30,11 +30,12 @@
>>>   static void explain(void)
>>>   {
>>>       fprintf(stderr, "Usage: ... qdisc add ... htb [default N] [r2q
>>> N]\n"
>>> -        "                      [direct_qlen P]\n"
>>> +        "                      [direct_qlen P] [offload]\n"
>>>           " default  minor id of class to which unclassified packets
>>> are sent {0}\n"
>>>           " r2q      DRR quantums are computed as rate in Bps/r2q
>>> {10}\n"
>>>           " debug    string of 16 numbers each 0-3 {0}\n\n"
>>>           " direct_qlen  Limit of the direct queue {in packets}\n"
>>> +        " offload  hardware offload\n"
>>
>> why 'offload hardware offload'? does not make sense to me and
> 
> "offload" is a new parameter, and "hardware offload" is the description,
> just like the other parameters above.
> 
>> you don't
>> reference hardware below.
> 
> Where should I reference it?

I see now. More words are needed to make it clear 'hardware offload' is
the explanation of offload. As it is, the words run together as 'offload
 hardware offload' which is the source of my confusion.