Re: [dpdk-dev] [PATCH v3 1/2] lib/librte_meter: add RFC4115 trTCM meter support

["Eelco Chaudron" <echaudro@redhat.com>]

On 21 Dec 2018, at 17:15, Dumitrescu, Cristian wrote:

> Hi Eelco,
>
> <snip>
>
>>
>> +/** trTCM parameters per metered traffic flow. The CIR, EIT, CBS and 
>> EBS
>
> Small typo here: EIT to be replaced by EIR.
>
>> +parameters only count bytes of IP packets and do not include link 
>> specific
>> +headers. The CBS and EBS need to be greater than zero if CIR and EIR 
>> are
>> +none-zero respectively.*/
>> +struct rte_meter_trtcm_rfc4115_params {
>> +	uint64_t cir; /**< Committed Information Rate (CIR). Measured in
>> bytes per second. */
>> +	uint64_t eir; /**< Excess Information Rate (EIR). Measured in bytes
>> per second. */
>> +	uint64_t cbs; /**< Committed Burst Size (CBS). Measured in bytes.
>> */
>> +	uint64_t ebs; /**< Excess Burst Size (EBS). Measured in bytes. */
>> +};
>> +
>
> <snip>
>
>> +static inline enum rte_meter_color __rte_experimental
>> +rte_meter_trtcm_rfc4115_color_blind_check(
>> +	struct rte_meter_trtcm_rfc4115 *m,
>> +	struct rte_meter_trtcm_rfc4115_profile *p,
>> +	uint64_t time,
>> +	uint32_t pkt_len)
>> +{
>> +	uint64_t time_diff_tc, time_diff_te, n_periods_tc, n_periods_te, 
>> tc,
>> te;
>> +
>> +	/* Bucket update */
>> +	time_diff_tc = time - m->time_tc;
>> +	time_diff_te = time - m->time_te;
>> +	n_periods_tc = time_diff_tc / p->cir_period;
>> +	n_periods_te = time_diff_te / p->eir_period;
>> +	m->time_tc += n_periods_tc * p->cir_period;
>> +	m->time_te += n_periods_te * p->eir_period;
>> +
>> +	tc = m->tc + n_periods_tc * p->cir_bytes_per_period;
>> +	if (tc > p->cbs)
>> +		tc = p->cbs;
>> +
>> +	te = m->te + n_periods_te * p->eir_bytes_per_period;
>> +	if (te > p->ebs)
>> +		te = p->ebs;
>> +
>> +	/* Color logic */
>> +	if (tc >= pkt_len) {
>> +		m->tc = tc - pkt_len;
>> +		m->te = te;
>> +		return e_RTE_METER_GREEN;
>> +	} else if (te >= pkt_len) {
>> +		m->tc = tc;
>> +		m->te = te - pkt_len;
>> +		return e_RTE_METER_YELLOW;
>> +	}
>> +
>> +	/* If we end up here the color is RED */
>> +	m->tc = tc;
>> +	m->te = te;
>> +	return e_RTE_METER_RED;
>> +}
>> +
>
> Since the branch (tc >= pkt_len) == TRUE always returns, I suggest we 
> remove the following "else", as it is redundant:
>
> 	/* Color logic */
> 	if (tc >= pkt_len) {
> 		m->tc = tc - pkt_len;
> 		m->te = te;
> 		return e_RTE_METER_GREEN;
> 	}
>
> 	if (te >= pkt_len) {
> 		m->tc = tc;
> 		m->te = te - pkt_len;
> 		return e_RTE_METER_YELLOW;
> 	}
>
> 	/* If we end up here the color is RED */
> 	m->tc = tc;
> 	m->te = te;
> 	return e_RTE_METER_RED;
>
>
>> +static inline enum rte_meter_color __rte_experimental
>> +rte_meter_trtcm_rfc4115_color_aware_check(
>> +	struct rte_meter_trtcm_rfc4115 *m,
>> +	struct rte_meter_trtcm_rfc4115_profile *p,
>> +	uint64_t time,
>> +	uint32_t pkt_len,
>> +	enum rte_meter_color pkt_color)
>> +{
>> +	uint64_t time_diff_tc, time_diff_te, n_periods_tc, n_periods_te, 
>> tc,
>> te;
>> +
>> +	/* Bucket update */
>> +	time_diff_tc = time - m->time_tc;
>> +	time_diff_te = time - m->time_te;
>> +	n_periods_tc = time_diff_tc / p->cir_period;
>> +	n_periods_te = time_diff_te / p->eir_period;
>> +	m->time_tc += n_periods_tc * p->cir_period;
>> +	m->time_te += n_periods_te * p->eir_period;
>> +
>> +	tc = m->tc + n_periods_tc * p->cir_bytes_per_period;
>> +	if (tc > p->cbs)
>> +		tc = p->cbs;
>> +
>> +	te = m->te + n_periods_te * p->eir_bytes_per_period;
>> +	if (te > p->ebs)
>> +		te = p->ebs;
>> +
>> +	/* Color logic */
>> +	if (pkt_color == e_RTE_METER_GREEN) {
>> +		if (tc >= pkt_len) {
>> +			m->tc = tc - pkt_len;
>> +			m->te = te;
>> +			return e_RTE_METER_GREEN;
>> +		} else if (te >= pkt_len) {
>> +			m->tc = tc;
>> +			m->te = te - pkt_len;
>> +			return e_RTE_METER_YELLOW;
>> +		}
>> +	} else if (pkt_color == e_RTE_METER_YELLOW && te >= pkt_len) {
>> +		m->tc = tc;
>> +		m->te = te - pkt_len;
>> +		return e_RTE_METER_YELLOW;
>> +	}
>> +
>> +	/* If we end up here the color is RED */
>> +	m->tc = tc;
>> +	m->te = te;
>> +	return e_RTE_METER_RED;
>> +}
>> +
>> +
>
> I suggest we follow the logic from the diagram in the RFC rather than 
> the logic in the text preceding the diagram. Although the two 
> descriptions are equivalent (after a bit of thinking), the diagram 
> seems more optimal to me:
>
> 	/* Color logic */
> 	if ((pkt_color == e_RTE_METER_GREEN) && (tc >= pkt_len)) {
> 		m->tc = tc - pkt_len;
> 		m->te = te;
> 		return e_RTE_METER_GREEN;
> 	}
>
> 	if ((pkt_color != e_RTE_METER_RED) && (te >= pkt_len)) {
> 		m->tc = tc;
> 		m->te = te - pkt_len;
> 		return e_RTE_METER_YELLOW;
> 	}
>
> 	/* If we end up here the color is RED */
> 	m->tc = tc;
> 	m->te = te;
> 	return e_RTE_METER_RED;
>
> <snip>
>
> Thanks,
> Cristian

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//Eelco