netdev - Re: [PATCH net-next 5/9] net/sched: support per action hw stats

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Message-ID: <ff11679c-2fe3-eeaf-44c9-6a96f43313dd@nvidia.com>
Date:   Sun, 5 Feb 2023 15:01:27 +0200
From:   Oz Shlomo <ozsh@...dia.com>
To:     Simon Horman <simon.horman@...igine.com>
Cc:     netdev@...r.kernel.org, Saeed Mahameed <saeedm@...dia.com>,
        Roi Dayan <roid@...dia.com>, Jiri Pirko <jiri@...dia.com>,
        Marcelo Ricardo Leitner <mleitner@...hat.com>,
        Baowen Zheng <baowen.zheng@...igine.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Edward Cree <ecree.xilinx@...il.com>
Subject: Re: [PATCH net-next 5/9] net/sched: support per action hw stats


On 03/02/2023 16:33, Simon Horman wrote:
> On Wed, Feb 01, 2023 at 06:10:34PM +0200, Oz Shlomo wrote:
>> There are currently two mechanisms for populating hardware stats:
>> 1. Using flow_offload api to query the flow's statistics.
>>     The api assumes that the same stats values apply to all
>>     the flow's actions.
>>     This assumption breaks when action drops or jumps over following
>>     actions.
>> 2. Using hw_action api to query specific action stats via a driver
>>     callback method. This api assures the correct action stats for
>>     the offloaded action, however, it does not apply to the rest of the
>>     actions in the flow's actions array.
>>
>> Extend the flow_offload stats callback to indicate that a per action
>> stats update is required.
>> Use the existing flow_offload_action api to query the action's hw stats.
>> In addition, currently the tc action stats utility only updates hw actions.
>> Reuse the existing action stats cb infrastructure to query any action
>> stats.
>>
>> Signed-off-by: Oz Shlomo <ozsh@...dia.com>
> ...
>
>> diff --git a/include/net/pkt_cls.h b/include/net/pkt_cls.h
>> index be21764a3b34..d4315757d1a2 100644
>> --- a/include/net/pkt_cls.h
>> +++ b/include/net/pkt_cls.h
>> @@ -292,9 +292,15 @@ static inline void tcf_exts_put_net(struct tcf_exts *exts)
>>   #define tcf_act_for_each_action(i, a, actions) \
>>   	for (i = 0; i < TCA_ACT_MAX_PRIO && ((a) = actions[i]); i++)
>>   
>> +static bool tc_act_in_hw(struct tc_action *act)
>> +{
>> +	return !!act->in_hw_count;
>> +}
>> +
>>   static inline void
>>   tcf_exts_hw_stats_update(const struct tcf_exts *exts,
>> -			 struct flow_stats *stats)
>> +			 struct flow_stats *stats,
>> +			 bool use_act_stats)
>>   {
>>   #ifdef CONFIG_NET_CLS_ACT
>>   	int i;
>> @@ -302,16 +308,18 @@ static inline void tcf_exts_put_net(struct tcf_exts *exts)
>>   	for (i = 0; i < exts->nr_actions; i++) {
>>   		struct tc_action *a = exts->actions[i];
>>   
>> -		/* if stats from hw, just skip */
>> -		if (tcf_action_update_hw_stats(a)) {
>> -			preempt_disable();
>> -			tcf_action_stats_update(a, stats->bytes, stats->pkts, stats->drops,
>> -						stats->lastused, true);
>> -			preempt_enable();
>> -
>> -			a->used_hw_stats = stats->used_hw_stats;
>> -			a->used_hw_stats_valid = stats->used_hw_stats_valid;
>> +		if (use_act_stats || tc_act_in_hw(a)) {
>> +			tcf_action_update_hw_stats(a);
> Hi Oz,
>
> I am a unclear why it is ok to continue here even if
> tcf_action_update_hw_stats() fails.  There seem to be cases other than
> !tc_act_in_hw() at play here, which prior to this patch, would execute the
> code below that is now outside this if clause.
You're right, my bad
>> +			continue;
>>   		}
>> +
>> +		preempt_disable();
>> +		tcf_action_stats_update(a, stats->bytes, stats->pkts, stats->drops,
>> +					stats->lastused, true);
>> +		preempt_enable();
>> +
>> +		a->used_hw_stats = stats->used_hw_stats;
>> +		a->used_hw_stats_valid = stats->used_hw_stats_valid;
>>   	}
>>   #endif
>>   }
>> @@ -769,6 +777,7 @@ struct tc_cls_matchall_offload {
>>   	enum tc_matchall_command command;
>>   	struct flow_rule *rule;
>>   	struct flow_stats stats;
>> +	bool use_act_stats;
>>   	unsigned long cookie;
>>   };
>>   
>> diff --git a/net/sched/act_api.c b/net/sched/act_api.c
>> index 917827199102..eda58b78da13 100644
>> --- a/net/sched/act_api.c
>> +++ b/net/sched/act_api.c
>> @@ -169,11 +169,6 @@ static bool tc_act_skip_sw(u32 flags)
>>   	return (flags & TCA_ACT_FLAGS_SKIP_SW) ? true : false;
>>   }
>>   
>> -static bool tc_act_in_hw(struct tc_action *act)
>> -{
>> -	return !!act->in_hw_count;
>> -}
>> -
>>   /* SKIP_HW and SKIP_SW are mutually exclusive flags. */
>>   static bool tc_act_flags_valid(u32 flags)
>>   {
>> @@ -308,9 +303,6 @@ int tcf_action_update_hw_stats(struct tc_action *action)
>>   	struct flow_offload_action fl_act = {};
>>   	int err;
>>   
>> -	if (!tc_act_in_hw(action))
>> -		return -EOPNOTSUPP;
>> -
>>   	err = offload_action_init(&fl_act, action, FLOW_ACT_STATS, NULL);
>>   	if (err)
>>   		return err;
> ...