linux-kernel - Re: [Intel-wired-lan] [PATCH v2 net] ixgbe: allow to increase MTU to some extent with XDP enabled

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Message-ID: <192d7154-78a6-e7a0-2810-109b864bbb4f@intel.com>
Date:   Tue, 31 Jan 2023 12:07:35 +0100
From:   Alexander Lobakin <alexandr.lobakin@...el.com>
To:     Jason Xing <kerneljasonxing@...il.com>
CC:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        <jesse.brandeburg@...el.com>, <anthony.l.nguyen@...el.com>,
        <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
        <pabeni@...hat.com>, <richardcochran@...il.com>, <ast@...nel.org>,
        <daniel@...earbox.net>, <hawk@...nel.org>,
        <john.fastabend@...il.com>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <intel-wired-lan@...ts.osuosl.org>,
        <bpf@...r.kernel.org>, Jason Xing <kernelxing@...cent.com>
Subject: Re: [Intel-wired-lan] [PATCH v2 net] ixgbe: allow to increase MTU to
 some extent with XDP enabled

From: Jason Xing <kerneljasonxing@...il.com>
Date: Tue, 31 Jan 2023 11:00:05 +0800

> On Mon, Jan 30, 2023 at 11:09 PM Maciej Fijalkowski
> <maciej.fijalkowski@...el.com> wrote:
>>
>> On Fri, Jan 27, 2023 at 08:20:18PM +0800, Jason Xing wrote:
>>> From: Jason Xing <kernelxing@...cent.com>
>>>
>>> I encountered one case where I cannot increase the MTU size directly
>>> from 1500 to 2000 with XDP enabled if the server is equipped with
>>> IXGBE card, which happened on thousands of servers in production
>>> environment.
>>
> 
>> You said in this thread that you've done several tests - what were they?
> 
> Tests against XDP are running on the server side when MTU varies from
> 1500 to 3050 (not including ETH_HLEN, ETH_FCS_LEN and VLAN_HLEN) for a

BTW, if ixgbe allows you to set MTU of 3050, it needs to be fixed. Intel
drivers at some point didn't include the second VLAN tag into account,
thus it was possible to trigger issues on Q-in-Q setups. AICS, not all
of them were fixed.

> few days.
> I choose the iperf tool to test the maximum throughput and observe the
> behavior when the machines are under greater pressure. Also, I use
> netperf to send different size packets to the server side with
> different modes (TCP_RR/_STREAM) applied.
[...]

Thanks,
Olek