RE:Re: [v1,net-next 3/4] net: qos: police action add index for tc flower offloading

RE:Re: [v1,net-next 3/4] net: qos: police action add index for tc flower offloading

[Po Liu]

> -----Original Message-----
> From: Jamal Hadi Salim <jhs@mojatatu.com>
> Sent: 2020年6月24日 20:45
> To: Po Liu <po.liu@nxp.com>; davem@davemloft.net; linux-
> kernel@vger.kernel.org; netdev@vger.kernel.org; idosch@idosch.org
> Cc: jiri@resnulli.us; vinicius.gomes@intel.com; vlad@buslov.dev; Claudiu
> Manoil <claudiu.manoil@nxp.com>; Vladimir Oltean
> <vladimir.oltean@nxp.com>; Alexandru Marginean
> <alexandru.marginean@nxp.com>; michael.chan@broadcom.com;
> vishal@chelsio.com; saeedm@mellanox.com; leon@kernel.org;
> jiri@mellanox.com; idosch@mellanox.com;
> alexandre.belloni@bootlin.com; UNGLinuxDriver@microchip.com;
> kuba@kernel.org; xiyou.wangcong@gmail.com;
> simon.horman@netronome.com; pablo@netfilter.org;
> moshe@mellanox.com; m-karicheri2@ti.com;
> andre.guedes@linux.intel.com; stephen@networkplumber.org; Edward
> Cree <ecree@solarflare.com>
> Subject: Re: [v1,net-next 3/4] net: qos: police action add index for tc
> flower offloading
> > 
> On 2020-06-23 7:52 p.m., Po Liu wrote:
> > Hi Jamal,
> >
> >
> 
> >>>> My question: Is this any different from how stats are structured?
> >>>
> 
> [..]
> >> My question: Why cant you apply the same semantics for the counters?
> >> Does your hardware have an indexed counter/stats table? If yes then
> >> you
> >
> > Yes,
> 
> That is the point i was trying to get to. Basically:
> You have a counter table which is referenced by "index"
> You also have a meter/policer table which is referenced by "index".

They should be one same group and same meaning.

> 
> For policers, they maintain their own stats. So when i say:
> tc ... flower ... action police ... index 5 The index referred to is in the
> policer table
> 

Sure. Means police with No. 5 entry. 

> But for other actions, example when i say:
> tc ... flower ... action drop index 10

Still the question, does gact action drop could bind with index? It doesn't meanful.

> The index is in the counter/stats table.
> It is not exactly "10" in hardware, the driver magically hides it from the
> user - so it could be hw counter index 1234

Not exactly. Current flower offloading stats means get the chain index for that flow filter. The other actions should bind to that chain index. Like IEEE802.1Qci, what I am doing is bind gate action to filter chain(mandatory). And also police action as optional. There is stream counter table which summary the counters pass gate action entry and police action entry for that chain index(there is a bit different if two chain sharing same action list).
One chain counter which tc show stats get counter source:
struct psfp_streamfilter_counters {
        u64 matching_frames_count;
        u64 passing_frames_count;
        u64 not_passing_frames_count;
        u64 passing_sdu_count;
        u64 not_passing_sdu_count;
        u64 red_frames_count;
};

When pass to the user space, summarize as:
        stats.pkts = counters.matching_frames_count +  counters.not_passing_sdu_count - filter->stats.pkts;
        stats.drops = counters.not_passing_frames_count + counters.not_passing_sdu_count +   counters.red_frames_count - filter->stats.drops;

But in software side, it is showing in the action list. And action gate and police exactly showing the counters that chain index. Not the true counters of index action gate or index police. This is the limitation of get the offloading stats.


> 
> The old approach is to assume the classifier (flower in this
> case) has a counter. The reason for this assumption is older hardware was
> designed to deal with a single action per match.
> So a counter to the filter is also the counter to the
> (single) action. I get the feeling your hardware fits in that space.

No, hardware could have gate+police actions but bind to one stream filter counter table in IEEE 802.1Qci.

> 
> Modern use cases have evolved from the ACL single match and action
> approach. Maintaining the old thought/architecture breaks in two use
> cases:
> 1) when you have multiple actions per policy filter. You need counter-per-
> action for various reasons

Action index only for set an action entry in hardware, and not get stats by that index.
So I don't think it is problem of  exposing action index to the driver break the rule. This is the limitation of get the offloading stats, there is no counters get by action index. 

> 2) Sharing of counters across filters and action. This can be achieve
> 
> tc supports the above and is sufficient to cover the old use cases.
> I am just worried, architecturally, we are restricting ourselves to the old
> scheme.
> 
> Another reason this is important is for the sake of analytics.
> A user space app can poll just for the stats table in hardware (or the
> cached version in the kernel) and reduce the amount of data crossing to
> user space..
> 
> cheers,
> jamal
> 
> 
> 
> 


Br,
Po Liu

Re: [v1,net-next 3/4] net: qos: police action add index for tc flower offloading

[Jamal Hadi Salim]

On 2020-06-24 8:34 p.m., Po Liu wrote:
> 
> 
>> -----Original Message-----

>> That is the point i was trying to get to. Basically:
>> You have a counter table which is referenced by "index"
>> You also have a meter/policer table which is referenced by "index".
> 
> They should be one same group and same meaning.
> 

Didnt follow. You mean the index is the same for both the
stat and policer?

>>
>> For policers, they maintain their own stats. So when i say:
>> tc ... flower ... action police ... index 5 The index referred to is in the
>> policer table
>>
> 
> Sure. Means police with No. 5 entry.
> 
>> But for other actions, example when i say:
>> tc ... flower ... action drop index 10
> 
> Still the question, does gact action drop could bind with index? It doesn't meanful.
> 

Depends on your hardware. From this discussion i am
trying to understand where the constraint is for your case.
Whether it is your h/w or the TSN spec.
For a sample counting which is flexible see here:
https://p4.org/p4-spec/docs/PSA.html#sec-counters

That concept is not specific to P4 but rather to
newer flow-based hardware.

More context:
The assumption these days is we can have a _lot_ of flows with a lot
of actions.
Then you want to be able to collect the stats separately, possibly one
counter entry for each action of interest.
Why is this important?f For analytics uses cases,
when you are retrieving the stats you want to reduce the amount of
data being retrieved. Typically these stats are polled every X seconds.
For starters, you dont dump filters (which in your case seems to be
the only way to get the stats).
In current tc, you dump the actions. But that could be improved so
you can just dump the stats. The mapping of stats index to actions
is known to the entity doing the dump.

Does that make sense?

>> The index is in the counter/stats table.
>> It is not exactly "10" in hardware, the driver magically hides it from the
>> user - so it could be hw counter index 1234
> 
> Not exactly. Current flower offloading stats means get the chain index for that flow filter. The other actions should bind to that chain index.
 >

So if i read correctly: You have an index per filter pointing to the
counter table.
Is this something _you_ decided to do in software or is it how the
hardware works? (note i referred to this as "legacy ACL" approach
earlier. It worked like that in old hardware because the main use
case was to have one action on a match (drop/accept kind).

>Like IEEE802.1Qci, what I am doing is bind gate action to filter chain(mandatory). And also police action as optional.

I cant seem to find this spec online. Is it freely available?
Also, if i understand you correctly you are saying according to this
spec you can only have the following type of policy:
tc .. filter match-spec-here .. \
action gate gate-action-attributes \
action police ...

That "action gate" MUST always be present
but "action police" is optional?

> There is stream counter table which summary the counters pass gate action entry and police action entry for that chain index(there is a bit different if two chain sharing same action list).
> One chain counter which tc show stats get counter source:
> struct psfp_streamfilter_counters {
>          u64 matching_frames_count;
>          u64 passing_frames_count;
>          u64 not_passing_frames_count;
>          u64 passing_sdu_count;
>          u64 not_passing_sdu_count;
>          u64 red_frames_count;
> };
>

Assuming psfp is something defined in IEEE802.1Qci and the spec will
describe these?
Is the filter  "index" pointing to one of those in some counter table?


> When pass to the user space, summarize as:
>          stats.pkts = counters.matching_frames_count +  counters.not_passing_sdu_count - filter->stats.pkts;
 >
>          stats.drops = counters.not_passing_frames_count + counters.not_passing_sdu_count +   counters.red_frames_count - filter->stats.drops;
>

Thanks for the explanation.
What is filter->stats?
The rest of those counters seem related to the gate action.
How do you account for policing actions?

cheers,
jamal

RE:Re: [v1,net-next 3/4] net: qos: police action add index for tc flower offloading

[Po Liu]

Hi Ido,

Sorry, ignore previous email.

> -----Original Message-----
> From: Ido Schimmel <idosch@idosch.org>
> Sent: 2020年6月23日 15:10
> To: Po Liu <po.liu@nxp.com>
> Cc: davem@davemloft.net; linux-kernel@vger.kernel.org;
> netdev@vger.kernel.org; jiri@resnulli.us; vinicius.gomes@intel.com;
> vlad@buslov.dev; Claudiu Manoil <claudiu.manoil@nxp.com>; Vladimir
> Oltean <vladimir.oltean@nxp.com>; Alexandru Marginean
> <alexandru.marginean@nxp.com>; michael.chan@broadcom.com;
> vishal@chelsio.com; saeedm@mellanox.com; leon@kernel.org;
> jiri@mellanox.com; idosch@mellanox.com;
> alexandre.belloni@bootlin.com; UNGLinuxDriver@microchip.com;
> kuba@kernel.org; jhs@mojatatu.com; xiyou.wangcong@gmail.com;
> simon.horman@netronome.com; pablo@netfilter.org;
> moshe@mellanox.com; m-karicheri2@ti.com;
> andre.guedes@linux.intel.com; stephen@networkplumber.org
> Subject: Re: [v1,net-next 3/4] net: qos: police action add index for tc
> flower offloading
> 
> On Tue, Jun 23, 2020 at 02:34:11PM +0800, Po Liu wrote:
> > From: Po Liu <Po.Liu@nxp.com>
> >
> > Hardware may own many entries for police flow. So that make one(or
> >  multi) flow to be policed by one hardware entry. This patch add the
> > police action index provide to the driver side make it mapping the
> > driver hardware entry index.
> 
> Maybe first mention that it is possible for multiple filters in software to
> share the same policer. Something like:
> 
> "
> It is possible for several tc filters to share the same police action by
> specifying the action's index when installing the filters.
> 
> Propagate this index to device drivers through the flow offload
> intermediate representation, so that drivers could share a single hardware
> policer between multiple filters.
> "
> 

Thanks, I would change this commit message.

> >
> > Signed-off-by: Po Liu <Po.Liu@nxp.com>
> > ---
> >  include/net/flow_offload.h | 1 +
> >  net/sched/cls_api.c        | 1 +
> >  2 files changed, 2 insertions(+)
> >
> > diff --git a/include/net/flow_offload.h b/include/net/flow_offload.h
> > index c2ef19c6b27d..eed98075b1ae 100644
> > --- a/include/net/flow_offload.h
> > +++ b/include/net/flow_offload.h
> > @@ -232,6 +232,7 @@ struct flow_action_entry {
> >                       bool                    truncate;
> >               } sample;
> >               struct {                                /* FLOW_ACTION_POLICE */
> > +                     u32                     index;
> >                       s64                     burst;
> >                       u64                     rate_bytes_ps;
> >                       u32                     mtu;
> > diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c index
> > 6aba7d5ba1ec..fdc4c89ca1fa 100644
> > --- a/net/sched/cls_api.c
> > +++ b/net/sched/cls_api.c
> > @@ -3659,6 +3659,7 @@ int tc_setup_flow_action(struct flow_action
> *flow_action,
> >                       entry->police.rate_bytes_ps =
> >                               tcf_police_rate_bytes_ps(act);
> >                       entry->police.mtu = tcf_police_tcfp_mtu(act);
> > +                     entry->police.index = act->tcfa_index;
> >               } else if (is_tcf_ct(act)) {
> >                       entry->id = FLOW_ACTION_CT;
> >                       entry->ct.action = tcf_ct_action(act);
> > --
> > 2.17.1
> >


Br,
Po Liu