netdev - Re: [patch net-next 00/10] net: allow user specify TC filter HW stats type

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Message-ID: <20200221102200.1978e10e@kicinski-fedora-PC1C0HJN>
Date:   Fri, 21 Feb 2020 10:22:00 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Jiri Pirko <jiri@...nulli.us>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, saeedm@...lanox.com,
        leon@...nel.org, michael.chan@...adcom.com, vishal@...lsio.com,
        jeffrey.t.kirsher@...el.com, idosch@...lanox.com,
        aelior@...vell.com, peppe.cavallaro@...com,
        alexandre.torgue@...com, jhs@...atatu.com,
        xiyou.wangcong@...il.com, pablo@...filter.org, mlxsw@...lanox.com,
        Edward Cree <ecree@...arflare.com>
Subject: Re: [patch net-next 00/10] net: allow user specify TC filter HW
 stats type

On Fri, 21 Feb 2020 10:56:33 +0100 Jiri Pirko wrote:
> From: Jiri Pirko <jiri@...lanox.com>
> 
> Currently, when user adds a TC filter and the filter gets offloaded,
> the user expects the HW stats to be counted and included in stats dump.
> However, since drivers may implement different types of counting, there
> is no way to specify which one the user is interested in.
> 
> For example for mlx5, only delayed counters are available as the driver
> periodically polls for updated stats.
> 
> In case of mlxsw, the counters are queried on dump time. However, the
> HW resources for this type of counters is quite limited (couple of
> thousands). This limits the amount of supported offloaded filters
> significantly. Without counter assigned, the HW is capable to carry
> millions of those.
> 
> On top of that, mlxsw HW is able to support delayed counters as well in
> greater numbers. That is going to be added in a follow-up patch.
> 
> This patchset allows user to specify one of the following types of HW
> stats for added fitler:
> any - current default, user does not care about the type, just expects
>       any type of stats.
> immediate - queried during dump time
> delayed - polled from HW periodically or sent by HW in async manner
> disabled - no stats needed

Hmm, but the statistics are on actions, it feels a little bit like we
are perpetuating the mistake of counting on filters here.

Would it not work to share actions between filters which don't need
fine grained stats if HW can do more filters than stats?

Let's CC Ed on this.