netdev - Re: [PATCH net-next v1 8/9] igc: Add support for exposing frame preemption stats registers

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Date:   Mon, 07 Dec 2020 14:29:54 -0800
From:   Vinicius Costa Gomes <vinicius.gomes@...el.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, jhs@...atatu.com, xiyou.wangcong@...il.com,
        jiri@...nulli.us, m-karicheri2@...com, vladimir.oltean@....com,
        Jose.Abreu@...opsys.com, po.liu@....com,
        intel-wired-lan@...ts.osuosl.org, anthony.l.nguyen@...el.com
Subject: Re: [PATCH net-next v1 8/9] igc: Add support for exposing frame
 preemption stats registers

Jakub Kicinski <kuba@...nel.org> writes:

> On Tue,  1 Dec 2020 20:53:24 -0800 Vinicius Costa Gomes wrote:
>> Expose the Frame Preemption counters, so the number of
>> express/preemptible packets can be monitored by userspace.
>> 
>> These registers are cleared when read, so the value shown is the
>> number of events that happened since the last read.
>> 
>> Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
>
> You mean expose in a register dump? That's not great user experience..

I can agree with that, even after some formatting on the ethtool side:

Preemption statistics:
    TX Preemption event counter: 14070
    Good TX Preemptable Packets: 201957
    Good TX Express Packets: 32031
    TX Preempted Packets: 13259
    RX Preemption event counter: 0
    Good RX Preemptable Packets: 0
    Good RX Preempted Packets: 0
    Preemption Exception Counter:
        OOO_SMDC 0
        OOO_FRAME 0
        OOO_FRAG 0
        MISS_FRAME_FRAG 0

It's less than ideal, but useful for development/debugging.

>
> Are there any stats that the standards mandate?

I just took abother look at the standard, mainly at the MIBs, there are
no statistics related to frame preemption that I could find, only
configuration stuff.

>
> It'd be great if we could come up with some common set and expose them
> via ethtool like the pause frame statistics.

Agreed, will drop this patch, until this common set is agreed upon.


Cheers,
-- 
Vinicius