Re: [dpdk-dev] [PATCH v2] Allow -ve frame_overhead values

["Dumitrescu, Cristian" <cristian.dumitrescu@intel.com>]

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of
> alanrobertsonatt@gmail.com
> Sent: Tuesday, January 16, 2018 3:32 PM
> To: Dumitrescu, Cristian <cristian.dumitrescu@intel.com>
> Cc: dev@dpdk.org; Alan Robertson <ar771e@att.com>; Alan Robertson
> <alan.robertson@att.com>
> Subject: [dpdk-dev] [PATCH v2] Allow -ve frame_overhead values
> 
> From: Alan Robertson <ar771e@att.com>
> 
> When forwarding traffic across a TDM network the ethernet header will
> be replaced with a ML-PPP one thereby reducing the size of the packet.
> 
> Signed-off-by: Alan Robertson <alan.robertson@att.com>
> ---
>  lib/librte_sched/rte_sched.c | 14 +++++++++++++-
>  lib/librte_sched/rte_sched.h |  5 +++--
>  2 files changed, 16 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/librte_sched/rte_sched.c b/lib/librte_sched/rte_sched.c
> index ad2f7c6d5..c971fd0d4 100644
> --- a/lib/librte_sched/rte_sched.c
> +++ b/lib/librte_sched/rte_sched.c
> @@ -187,7 +187,7 @@ struct rte_sched_port {
>  	uint32_t n_pipes_per_subport;
>  	uint32_t rate;
>  	uint32_t mtu;
> -	uint32_t frame_overhead;
> +	int32_t frame_overhead;
>  	uint16_t qsize[RTE_SCHED_TRAFFIC_CLASSES_PER_PIPE];
>  	uint32_t n_pipe_profiles;
>  	uint32_t pipe_tc3_rate_max;
> @@ -1591,6 +1591,10 @@ grinder_credits_check(struct rte_sched_port
> *port, uint32_t pos)
>  	uint32_t pipe_tc_credits = pipe->tc_credits[tc_index];
>  	int enough_credits;
> 
> +#ifdef RTE_SCHED_DEBUG
> +	assert((int)(pkt->pkt_len + port->frame_overhead) > 0);
> +#endif /* RTE_SCHED_DEBUG */
> +
>  	/* Check queue credits */
>  	enough_credits = (pkt_len <= subport_tb_credits) &&
>  		(pkt_len <= subport_tc_credits) &&
> @@ -1629,6 +1633,10 @@ grinder_credits_check(struct rte_sched_port
> *port, uint32_t pos)
>  	uint32_t pipe_tc_ov_credits = pipe_tc_ov_mask1[tc_index];
>  	int enough_credits;
> 
> +#ifdef RTE_SCHED_DEBUG
> +	assert((int)(pkt->pkt_len + port->frame_overhead) > 0);
> +#endif /* RTE_SCHED_DEBUG */
> +
>  	/* Check pipe and subport credits */
>  	enough_credits = (pkt_len <= subport_tb_credits) &&
>  		(pkt_len <= subport_tc_credits) &&
> @@ -1663,6 +1671,10 @@ grinder_schedule(struct rte_sched_port *port,
> uint32_t pos)
>  	if (!grinder_credits_check(port, pos))
>  		return 0;
> 
> +#ifdef RTE_SCHED_DEBUG
> +	assert((int)(pkt->pkt_len + port->frame_overhead) > 0);
> +#endif /* RTE_SCHED_DEBUG */
> +
>  	/* Advance port time */
>  	port->time += pkt_len;
> 
> diff --git a/lib/librte_sched/rte_sched.h b/lib/librte_sched/rte_sched.h
> index 5d2a688dc..3e135c1e5 100644
> --- a/lib/librte_sched/rte_sched.h
> +++ b/lib/librte_sched/rte_sched.h
> @@ -190,8 +190,9 @@ struct rte_sched_port_params {
>  	uint32_t mtu;                    /**< Maximum Ethernet frame size
>  					  * (measured in bytes).
>  					  * Should not include the framing
> overhead. */
> -	uint32_t frame_overhead;         /**< Framing overhead per packet
> -					  * (measured in bytes) */
> +	int32_t frame_overhead;
> +	/**< Framing overhead per packet (measured in bytes).
> +	 * Can have negative value. */
>  	uint32_t n_subports_per_port;    /**< Number of subports */
>  	uint32_t n_pipes_per_subport;    /**< Number of pipes per subport
> */
>  	uint16_t qsize[RTE_SCHED_TRAFFIC_CLASSES_PER_PIPE];
> --
> 2.11.0
> 

Hi Alan,

This patch is straightforward now, but it has build failures, do you plan to send a v3 to fix them?

Essentially, you need to replace assert() calls from your code with RTE_ASSERT/RTE_VERIFY from rte_debug.h.

Also, I don't see the point in having the assert in grinder_credits_check(), as this is purely a check on packet length, not credits.  IMO we should have the assert in grinder_schedule() as the first instruction, before the call to grinder_credits_check(), as this is a sort of validating the inputs into the scheduling decision.

Thanks,
Cristian