netdev - Re: [PATCH net-next v2] net/sched: act_police: add support for packet-per-second policing

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Date:   Mon, 1 Feb 2021 13:33:53 +0100
From:   Simon Horman <simon.horman@...ronome.com>
To:     Jamal Hadi Salim <jhs@...atatu.com>
Cc:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...lanox.com>, netdev@...r.kernel.org,
        oss-drivers@...ronome.com, Baowen Zheng <baowen.zheng@...igine.com>
Subject: Re: [PATCH net-next v2] net/sched: act_police: add support for
 packet-per-second policing

On Fri, Jan 29, 2021 at 09:30:00AM -0500, Jamal Hadi Salim wrote:
> On 2021-01-29 5:28 a.m., Simon Horman wrote:
> > From: Baowen Zheng <baowen.zheng@...igine.com>
> > 
> > Allow a policer action to enforce a rate-limit based on packets-per-second,
> > configurable using a packet-per-second rate and burst parameters. This may
> > be used in conjunction with existing byte-per-second rate limiting in the
> > same policer action.
> > 
> > e.g.
> > tc filter add dev tap1 parent ffff: u32 match \
> >                u32 0 0 police pkts_rate 3000 pkts_burst 1000
> > 
> > Testing was unable to uncover a performance impact of this change on
> > existing features.
> > 
> 
> Ido's comment is important: Why not make packet rate vs byte rate
> mutually exclusive? If someone uses packet rate then you make sure
> they dont interleave with attributes for byte rate and vice-versa.
> 
> I dont see featurewise impact - but certainly the extra check
> in the fastpath will likely have a small performance impact
> at high rates. Probably not a big deal (if Eric D. is not looking).
> Side note: this policer (with your addition) is now supporting 3 policer
> algorithms - i wonder if it makes sense to start spliting the different
> policers (which will solve the performance impact).

Sorry, I somehow missed Ido's email until you and he pointed it out
in this thread.

Regarding splitting up the policer action. I think there is some value to
the current setup in terms of code re-use and allowing combinations of
features. But I do agree it would be a conversation worth having at some
point.