netdev - Re: [RFC v3 net-next] net: core: devlink: add 'dropped' stats field for DROP trap action

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Message-ID: <AM0P190MB07389749FDC9EE63F1F8435CE4B69@AM0P190MB0738.EURP190.PROD.OUTLOOK.COM>
Date:   Mon, 1 Feb 2021 14:54:55 +0000
From:   Oleksandr Mazur <oleksandr.mazur@...ision.eu>
To:     Jakub Kicinski <kuba@...nel.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "jiri@...dia.com" <jiri@...dia.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC v3 net-next] net: core: devlink: add 'dropped' stats field
 for DROP trap action


On Fri, 29 Jan 2021 11:15:43 +0000 Oleksandr Mazur wrote:
> > >Thinking about it again - if the action can be changed wouldn't it 
> > >be best for the user to actually get a "HW condition hit" counter,
> >> which would increment regardless of SW config (incl. policers)?  
> >
> > >Otherwise if admin logs onto the box and temporarily enables a trap 
> >> for debug this count would disappear.  
>> 
>> But still this counter makes sense only for 'drop' action.

>Okay, well, "dropped while trap was disabled" seems a lot less useful
>of a definition than "number of times this trap would trigger" but if
>that's all the HW can provide then it is what it is.

>Does the HW also count packets dropped because of overload / overflow
>or some other event, or purely dropped because disabled?

Hw starts counting traffic (hw drops) only when action has been explicitly set to be 'DROP';