netdev - Re: [RFC v3 net-next 13/18] net/sched: Introduce the TBS Qdisc

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Message-ID: <768e8da5-502e-d36f-0f32-9324eaca4a1d@intel.com>
Date:   Mon, 23 Apr 2018 11:21:34 -0700
From:   Jesus Sanchez-Palencia <jesus.sanchez-palencia@...el.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     netdev@...r.kernel.org, jhs@...atatu.com, xiyou.wangcong@...il.com,
        jiri@...nulli.us, vinicius.gomes@...el.com,
        richardcochran@...il.com, intel-wired-lan@...ts.osuosl.org,
        anna-maria@...utronix.de, henrik@...tad.us, john.stultz@...aro.org,
        levi.pearson@...man.com, edumazet@...gle.com, willemb@...gle.com,
        mlichvar@...hat.com
Subject: Re: [RFC v3 net-next 13/18] net/sched: Introduce the TBS Qdisc

Hi Thomas,


On 03/21/2018 06:46 AM, Thomas Gleixner wrote:
> On Tue, 6 Mar 2018, Jesus Sanchez-Palencia wrote:
>> +struct tbs_sched_data {
>> +	bool sorting;
>> +	int clockid;
>> +	int queue;
>> +	s32 delta; /* in ns */
>> +	ktime_t last; /* The txtime of the last skb sent to the netdevice. */
>> +	struct rb_root head;
> 
> Hmm. You are reimplementing timerqueue open coded. Have you checked whether
> you could reuse the timerqueue implementation?
> 
> That requires to add a timerqueue node to struct skbuff
> 
> @@ -671,7 +671,8 @@ struct sk_buff {
>  				unsigned long		dev_scratch;
>  			};
>  		};
> -		struct rb_node	rbnode; /* used in netem & tcp stack */
> +		struct rb_node		rbnode; /* used in netem & tcp stack */
> +		struct timerqueue_node	tqnode;
>  	};
>  	struct sock		*sk;
> 
> Then you can use timerqueue_head in your scheduler data and all the open
> coded rbtree handling goes away.


I just noticed that doing the above increases the size of struct sk_buff by 8
bytes - struct timerqueue_node is 32bytes long while struct rb_node is only
24bytes long.

Given the feedback we got here before against touching struct sk_buff at all for
non-generic use cases, I will keep the implementation of sch_tbs.c as is, thus
keeping the open-coded version for now, ok?

Thanks,
Jesus


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