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

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Message-ID: <VI1PR05MB35209D291846A0D2FA9AFD08BF170@VI1PR05MB3520.eurprd05.prod.outlook.com>
Date:   Fri, 12 Jan 2018 00:05:29 +0000
From:   Yuval Mintz <yuvalm@...lanox.com>
To:     Jakub Kicinski <kubakici@...pl>
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

> > > > +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.

*we* surely understand that now. I'm just mentioning it might
confuse future offloaders; No strong objection here.
And I agree the alternative [passing pointers to each momentary stat]
is quite ugly.