Re: [dpdk-dev] [RFC PATCH v4 1/3] sched: add PIE based congestion management

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

Hi Wojciech,

> -----Original Message-----
> From: Liguzinski, WojciechX <wojciechx.liguzinski@intel.com>
> Sent: Monday, July 5, 2021 9:04 AM
> To: dev@dpdk.org; Singh, Jasvinder <jasvinder.singh@intel.com>;
> Dumitrescu, Cristian <cristian.dumitrescu@intel.com>
> Cc: Dharmappa, Savinay <savinay.dharmappa@intel.com>; Ajmera, Megha
> <megha.ajmera@intel.com>
> Subject: [RFC PATCH v4 1/3] sched: add PIE based congestion management
> 
> Implement PIE based congestion management based on rfc8033
> 
> Signed-off-by: Liguzinski, WojciechX <wojciechx.liguzinski@intel.com>
> ---
>  drivers/net/softnic/rte_eth_softnic_tm.c |   6 +-
>  lib/sched/meson.build                    |  10 +-
>  lib/sched/rte_pie.c                      |  82 +++++
>  lib/sched/rte_pie.h                      | 393 +++++++++++++++++++++++
>  lib/sched/rte_sched.c                    | 229 +++++++++----
>  lib/sched/rte_sched.h                    |  53 ++-
>  lib/sched/version.map                    |   3 +
>  7 files changed, 685 insertions(+), 91 deletions(-)
>  create mode 100644 lib/sched/rte_pie.c
>  create mode 100644 lib/sched/rte_pie.h
> 

<snip>

> diff --git a/lib/sched/rte_sched.h b/lib/sched/rte_sched.h
> index c1a772b70c..a5fe6266cd 100644
> --- a/lib/sched/rte_sched.h
> +++ b/lib/sched/rte_sched.h
> @@ -61,9 +61,10 @@ extern "C" {
>  #include <rte_mbuf.h>
>  #include <rte_meter.h>
> 
> -/** Random Early Detection (RED) */
> -#ifdef RTE_SCHED_RED
> +/** Active Queue Management */
> +#ifdef RTE_SCHED_AQM

We typically use the term Congestion Management for this, it is already used in rte_tm.h for example. Please replace AQM with CMAN _everywhere_:

#ifdef RTE_SCHED_CMAN

>  #include "rte_red.h"
> +#include "rte_pie.h"
>  #endif
> 
>  /** Maximum number of queues per pipe.
> @@ -110,6 +111,28 @@ extern "C" {
>  #define RTE_SCHED_FRAME_OVERHEAD_DEFAULT      24
>  #endif
> 
> +/**
> + * Active Queue Management (AQM) mode
> + *
> + * This is used for controlling the admission of packets into a packet queue
> or
> + * group of packet queues on congestion.
> + *
> + * The *Random Early Detection (RED)* algorithm works by proactively
> dropping
> + * more and more input packets as the queue occupancy builds up. When
> the queue
> + * is full or almost full, RED effectively works as *tail drop*. The *Weighted
> + * RED* algorithm uses a separate set of RED thresholds for each packet
> color.
> + *
> + * Similar to RED, Proportional Integral Controller Enhanced (PIE) randomly
> + * drops a packet at the onset of the congestion and tries to control the
> + * latency around the target value. The congestion detection, however, is
> based
> + * on the queueing latency instead of the queue length like RED. For more
> + * information, refer RFC8033.
> + */
> +enum rte_sched_aqm_mode {
> +	RTE_SCHED_AQM_WRED, /**< Weighted Random Early Detection
> (WRED) */
> +	RTE_SCHED_AQM_PIE,  /**< Proportional Integral Controller
> Enhanced (PIE) */
> +};
> +
>  /*
>   * Pipe configuration parameters. The period and credits_per_period
>   * parameters are measured in bytes, with one byte meaning the time
> @@ -174,9 +197,17 @@ struct rte_sched_subport_params {
>  	/** Max allowed profiles in the pipe profile table */
>  	uint32_t n_max_pipe_profiles;
> 
> -#ifdef RTE_SCHED_RED
> -	/** RED parameters */
> -	struct rte_red_params
> red_params[RTE_SCHED_TRAFFIC_CLASSES_PER_PIPE][RTE_COLORS];
> +#ifdef RTE_SCHED_AQM
> +	/** Active Queue Management mode */
> +	enum rte_sched_aqm_mode aqm;
> +
> +	RTE_STD_C11
> +	union {
> +		/** WRED parameters */
> +		struct rte_red_params
> wred_params[RTE_SCHED_TRAFFIC_CLASSES_PER_PIPE][RTE_COLORS];
> +		/** PIE parameters */
> +		struct rte_pie_params
> pie_params[RTE_SCHED_TRAFFIC_CLASSES_PER_PIPE];
> +	};
>  #endif
>  };
> 

We cannot have definitions of global variables in header files, we can only have extern declarations in header files and the definition in .c files.

Please create a global structure called rte_sched_cman_params that includes the both the WRED and the PIE parameters:

struct rte_sched_cman_params {
	enum rte_sched_cman cman_mode;

	union {
		/** WRED parameters */
		struct rte_red_params red_params[RTE_SCHED_TRAFFIC_CLASSES_PER_PIPE][RTE_COLORS];

		/** PIE parameters */
		struct rte_pie_params pie_params[RTE_SCHED_TRAFFIC_CLASSES_PER_PIPE];
	};
};

Then please instantiate this structure in one of the .c files.

Please do not rename red to wred (as done in multiple places in this patch set).

> @@ -208,9 +239,9 @@ struct rte_sched_subport_stats {
>  	/** Number of bytes dropped for each traffic class */
>  	uint64_t
> n_bytes_tc_dropped[RTE_SCHED_TRAFFIC_CLASSES_PER_PIPE];
> 
> -#ifdef RTE_SCHED_RED
> -	/** Number of packets dropped by red */
> -	uint64_t
> n_pkts_red_dropped[RTE_SCHED_TRAFFIC_CLASSES_PER_PIPE];
> +#ifdef RTE_SCHED_AQM
> +	/** Number of packets dropped by active queue management
> scheme */
> +	uint64_t
> n_pkts_aqm_dropped[RTE_SCHED_TRAFFIC_CLASSES_PER_PIPE];
>  #endif
>  };
> 

Please remove the #ifdefs and consolidate these stats into a single generic structure:

struct rte_sched_subport_stats {
	...
	uint64_t n_pkts_cman_dropped[RTE_SCHED_TRAFFIC_CLASSES_PER_PIPE];
	...
};

You can use the n_pkts_cman_dropped field for both WRED and PIE, depending on the cman_mode.

> @@ -222,9 +253,9 @@ struct rte_sched_queue_stats {
>  	/** Packets dropped */
>  	uint64_t n_pkts_dropped;
> 
> -#ifdef RTE_SCHED_RED
> -	/** Packets dropped by RED */
> -	uint64_t n_pkts_red_dropped;
> +#ifdef RTE_SCHED_AQM
> +	/** Packets dropped by active queue management scheme */
> +	uint64_t n_pkts_aqm_dropped;
>  #endif
> 
>  	/** Bytes successfully written */

Please remove the #ifdefs and consolidate these stats into a single generic structure:

struct rte_sched_queue_stats {
	...
	uint64_t n_pkts_cman_dropped;
	...
};

You can use the n_pkts_cman_dropped field for both WRED and PIE, depending on the cman_mode.

Regards,
Cristian