netdev - Re: [patch net-next RFC 0/8] Add support for pipeline debug (dpipe)

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Message-ID: <20170216164029.GE17550@lunn.ch>
Date:   Thu, 16 Feb 2017 17:40:29 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, arkadis@...lanox.com,
        idosch@...lanox.com, mlxsw@...lanox.com, jhs@...atatu.com,
        ivecera@...hat.com, roopa@...ulusnetworks.com,
        f.fainelli@...il.com, vivien.didelot@...oirfairelinux.com,
        john.fastabend@...il.com
Subject: Re: [patch net-next RFC 0/8] Add support for pipeline debug (dpipe)

On Thu, Feb 16, 2017 at 05:20:00PM +0100, Jiri Pirko wrote:
> Thu, Feb 16, 2017 at 05:11:50PM CET, andrew@...n.ch wrote:
> >On Thu, Feb 16, 2017 at 04:22:36PM +0100, Jiri Pirko wrote:
> >> From: Jiri Pirko <jiri@...lanox.com>
> >> 
> >> Arkadi says:
> >
> >Hi Jiri, Arkadi
> >
> >It is not mentioned here, but i assume you have a followup patchset
> >which extends the devlink command to enumerate what tables are
> >available and to print them?
> 
> DEVLINK_CMD_DPIPE_TABLES_GET
> command gets you all tables. But it gets it with the content. I guess
> there could be some command to instruct devlink just to dump tables
> without the content.

This does not sound like it will scale very well, as the number of
tables increases. Also, at least in the DSA world, getting a table can
be an expensive operation, lots of MDIO/SPI/I2C transactions. I'd
prefer to be able to just get one specific table, rather than dump
them all.

I can however see cases when it does make sense to have an atomic,
dump everything operation, where you can trust to be consistent across
tables.

> >Hopefully it will be more obvious when the user space patches are
> >available.
> 
> I'll ask Arkadi to send the devlink userspace patches as RFC as well.

Great, thanks.

       Andrew