netdev - Re: [PATCH RFC 0/2] ethtool: Add actual port speed reporting

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Message-ID: <7a681afa-a5fa-3039-873c-d13617484cc9@gmail.com>
Date:   Thu, 3 Nov 2016 18:59:11 +0200
From:   Gal Pressman <galp.dev@...il.com>
To:     "Mintz, Yuval" <Yuval.Mintz@...ium.com>,
        Gal Pressman <galp@...lanox.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "John W. Linville" <linville@...driver.com>,
        Vidya Sagar Ravipati <vidya@...ulusnetworks.com>,
        Saeed Mahameed <saeedm@...lanox.com>
Cc:     David Decotigny <decot@...glers.com>,
        Ben Hutchings <ben@...adent.org.uk>
Subject: Re: [PATCH RFC 0/2] ethtool: Add actual port speed reporting



On 02/11/2016 17:50, Mintz, Yuval wrote:
>> Sending RFC to get feedback for the following ethtool proposal:
>>
>> In some cases such as virtual machines and multi functions (SR-IOV), the actual
>> bandwidth exposed for each machine is not accurately shown in ethtool.
>> Currently ethtool shows only physical port link speed.
>> In our case we would like to show the virtual port operational link speed which
>> in some cases is less than the physical port speed.
>>
>> This will give users better visibility for the actual speed running on their device.
>>
>> $ ethtool ens6
>> ...
>> Speed: 50000Mb/s
>> Actual speed: 25000Mb/s
> 
> Not saying this is a bad thing, but where exactly is it listed that ethtool has
> to show the physical port speed?
> E.g., bnx2x shows the logical speed instead, and has been doing that for years.
> [Perhaps that's a past wrongness, but that's how it goes].
> 
> And besides, one can argue that in the SR-IOV scenario the VF has no business
> knowing the physical port speed.
> 

Good point, but there are more use-cases we should consider.
For example, when using Multi-Host/Flex-10/Multi-PF each PF should
be able to query both physical port speed and actual speed.