netdev - Re: [patch net-next 3/5] net: sch: prio: Add offload ability to PRIO qdisc

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Date:   Thu, 11 Jan 2018 16:00:13 -0800
From:   Jakub Kicinski <kubakici@...pl>
To:     Yuval Mintz <yuvalm@...lanox.com>
Cc:     Jiri Pirko <jiri@...nulli.us>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Nogah Frankel <nogahf@...lanox.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "Ido Schimmel" <idosch@...lanox.com>, mlxsw <mlxsw@...lanox.com>,
        "jhs@...atatu.com" <jhs@...atatu.com>,
        "xiyou.wangcong@...il.com" <xiyou.wangcong@...il.com>
Subject: Re: [patch net-next 3/5] net: sch: prio: Add offload ability to
 PRIO qdisc

On Thu, 11 Jan 2018 23:50:27 +0000, Yuval Mintz wrote:
> > > +struct tc_prio_qopt_offload_params {
> > > +	int bands;
> > > +	u8 priomap[TC_PRIO_MAX + 1];
> > > +	/* In case that a prio qdisc is offloaded and now is changed to a
> > > +	 * non-offloadedable config, it needs to update the backlog value
> > > +	 * to negate the HW backlog value.
> > > +	 */
> > > +	u32 *backlog;
> > > +};  
> > 
> > Could we please pass the full qstats on replace and destroy.  This
> > simplifies the driver code and allows handling the qlen as well as
> > backlog.  Please see the 2 patch series I sent earlier yesterday.  
> 
> That might give the false impression that offloading driver is expected
> to correct all the qstats fields during destruction, whereas for most of
> them it doesn't seem appropriate.

The driver is supposed to return the momentary stats to their
original/SW-only value.  And the driver knows exactly which stats 
those are, just look at your patch 5, you handle backlog completely
differently than other stats already.