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

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Date:   Sun, 5 Feb 2023 15:02:28 +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 16:51, 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>
>> ---
>>   include/net/flow_offload.h |  1 +
>>   include/net/pkt_cls.h      | 29 +++++++++++++++++++----------
>>   net/sched/act_api.c        |  8 --------
>>   net/sched/cls_flower.c     |  2 +-
>>   net/sched/cls_matchall.c   |  2 +-
>>   5 files changed, 22 insertions(+), 20 deletions(-)
>>
>> diff --git a/include/net/flow_offload.h b/include/net/flow_offload.h
>> index d177bf5f0e1a..27decadd4f5f 100644
>> --- a/include/net/flow_offload.h
>> +++ b/include/net/flow_offload.h
>> @@ -597,6 +597,7 @@ struct flow_cls_offload {
>>   	unsigned long cookie;
>>   	struct flow_rule *rule;
>>   	struct flow_stats stats;
>> +	bool use_act_stats;
>>   	u32 classid;
>>   };
> Hi Oz,
>
> It's probably not important, but I thought it is worth bringing
> to your attention.
>
> The placement of use_act_stats above  puts it on a different
> cacheline (on x86_64) to stats. Which does not seem to be idea
> as those fields are accessed together.
>
> There is a 4 byte hole immediately above above cookie,
> on the same cacheline as stats, which can accommodate use_act_stats.

Good catch.

I will move use_act_stats for better cache alignment.

>>   
>> 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
> ...
>
>> @@ -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;
>>   };
> I believe the same logic applies to this change too.
>
> ...
>
>> diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
>> index cb04739a13ce..885c95191ccf 100644
>> --- a/net/sched/cls_flower.c
>> +++ b/net/sched/cls_flower.c
>> @@ -502,7 +502,7 @@ static void fl_hw_update_stats(struct tcf_proto *tp, struct cls_fl_filter *f,
>>   	tc_setup_cb_call(block, TC_SETUP_CLSFLOWER, &cls_flower, false,
>>   			 rtnl_held);
>>   
>> -	tcf_exts_hw_stats_update(&f->exts, &cls_flower.stats);
>> +	tcf_exts_hw_stats_update(&f->exts, &cls_flower.stats, cls_flower.use_act_stats);
>>   }
>>   
>>   static void __fl_put(struct cls_fl_filter *f)
>> diff --git a/net/sched/cls_matchall.c b/net/sched/cls_matchall.c
>> index b3883d3d4dbd..fa3bbd187eb9 100644
>> --- a/net/sched/cls_matchall.c
>> +++ b/net/sched/cls_matchall.c
>> @@ -331,7 +331,7 @@ static void mall_stats_hw_filter(struct tcf_proto *tp,
>>   
>>   	tc_setup_cb_call(block, TC_SETUP_CLSMATCHALL, &cls_mall, false, true);
>>   
>> -	tcf_exts_hw_stats_update(&head->exts, &cls_mall.stats);
>> +	tcf_exts_hw_stats_update(&head->exts, &cls_mall.stats, cls_mall.use_act_stats);
>>   }
>>   
>>   static int mall_dump(struct net *net, struct tcf_proto *tp, void *fh,