netdev - Re: [PATCH V1 net-next 0/5] Add devlink support to ena

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Message-ID: <pj41zltu0vn9o7.fsf@u570694869fb251.ant.amazon.com>
Date:   Thu, 12 Jan 2023 15:47:13 +0200
From:   Shay Agroskin <shayagr@...zon.com>
To:     Gal Pressman <gal@...dia.com>, Jakub Kicinski <kuba@...nel.org>
CC:     "Arinzon, David" <darinzon@...zon.com>,
        David Miller <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "Machulsky, Zorik" <zorik@...zon.com>,
        "Matushevsky, Alexander" <matua@...zon.com>,
        "Bshara, Saeed" <saeedb@...zon.com>,
        "Bshara, Nafea" <nafea@...zon.com>,
        "Saidi, Ali" <alisaidi@...zon.com>,
        "Kiyanovski, Arthur" <akiyano@...zon.com>,
        "Dagan, Noam" <ndagan@...zon.com>,
        "Itzko, Shahar" <itzko@...zon.com>,
        "Abboud, Osama" <osamaabb@...zon.com>
Subject: Re: [PATCH V1 net-next 0/5] Add devlink support to ena


Gal Pressman <gal@...dia.com> writes:

> On 11/01/2023 22:00, Jakub Kicinski wrote:
>> On Wed, 11 Jan 2023 19:31:39 +0000 Arinzon, David wrote:
>>> If the packet network headers are not within the size of the 
>>> LLQ entry, then the packet will
>>> be dropped. So I'll say that c) describes the impact the best 
>>> given that certain types of
>>> traffic will not succeed or have disruptions due to dropped TX 
>>> packets.
>> 
>> I see. Sounds like it could be a fit for
>> DEVLINK_ATTR_ESWITCH_INLINE_MODE ? But that one configures the 
>> depth of
>> the headers copied inline, rather than bytes. We could add a 
>> value for
>> "tunneled" and have that imply 256B LLQ in case of ena.
>> 
>> The other option is to introduce the concept of "max length of 
>> inline
>> data" to ethtool, and add a new netlink attribute to ethtool 
>> -g.
>
> TX copybreak? When the user sets it to > 96 bytes, use the large 
> LLQ.
>
> BTW, shouldn't ethtool's tx_push reflect the fact that LLQs are 
> being
> used? I don't see it used in ena.

Using tx copybreak does sound like it can work for our use 
case. Thanks for the tip Gal (:

Jakub, do you see an issue with utilizing tx_copybreak ethtool 
parameter instead of the devlink param in this patchset ?

Thanks,
Shay