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RDMA PCC

Programmable Congestion Control (PCC) APIs to configure user algorithms and parameters for a RDMA device.

Example​

Here is an example of how to use the PCC APIs.

example_pcc.cc
#include <libmango.h>

typedef strict {
  ...
} my_algo_params;

static const my_algo_params initial_params = {
  ...
};

void
my_algo (void *params)
{
  my_algo_params *p = (my_algo_params *) params;
  unsigned int cnp = mango_pcc_event_cnp_cnt ();
  unsigned int cwnd = mango_pcc_window_current ();
  unsigned int nwnd;

  // calculate new window size
  nwnd = ...

  mango_pcc_window_update (nwnd);

  ...
}

int main() {
  // Create a PCC handle
  mango_pcc_h pcc;
  mango_pcc_create ("roce0", &pcc);

  // Configure PCC parameters
  mango_pcc_config_t config;
  config.option = MANGO_PCC_CONFIG_INTERVAL;
  config.value.interval_us = 60;
  mango_pcc_ctrl_config (pcc, &config);

  // Register PCC algorithm
  mango_pcc_ctrl_reg_algo (pcc, 1, algo, &initial_params, sizeof (initial_params));

  // Run PCC engine with 4 threads
  mango_pcc_ctrl_run (pcc, 4);
  ...

  // Stop PCC engine
  mango_pcc_ctrl_stop (pcc);
  mango_pcc_destroy (pcc);

  return 0;
}

Datatypes​

mango_pcc_algo_fn​

typedef void(void *) mango_pcc_algo_fn;

User-provided CC algorithm function.

mango_pcc_config_option_e​

typedef enum _mango_pcc_config_option mango_pcc_config_option_e;

PCC configuration options.

Values

MANGO_PCC_CONFIG_INTERVALAlgorithm execution interval

mango_pcc_config_t​

typedef struct _mango_pcc_config mango_pcc_config_t;

PCC configuration value type.

Members

optionPCC configuration option
interval_usmicroseconds

Functions​

mango_pcc_create​

mango_status_e mango_pcc_create(const char *roce_dev_name, mango_pcc_h *pcc)

Create a PCC handle.

Parameters

  • in roce_dev_name Name of the roce device.
  • out pcc Pointer to receive the newly created PCC handle.

Returns 0 on success, Otherwise, a negative error value.

mango_pcc_destroy​

mango_status_e mango_pcc_destroy(mango_pcc_h pcc)

Destroy a PCC handle.

Parameters

  • in pcc The PCC handle to destroy.

Returns 0 on success, Otherwise, a negative error value.

mango_pcc_get_context​

mango_context_h mango_pcc_get_context(mango_pcc_h pcc)

Get the context handle from a pcc handle.

Parameters

  • in pcc The PCC handle.

Returns the context handle on success, Otherwise, nullptr.

note

DO NOT CALL mango_context_destroy with the result; it will be destroyed when mango_pcc_destroy is called.

mango_pcc_ctrl_config​

mango_status_e mango_pcc_ctrl_config(mango_pcc_h pcc,
                                     const mango_pcc_config_t *config)

Set a PCC configuration value.

Parameters

  • in pcc The PCC handle.
  • in config The configuration value.

Returns 0 on success, Otherwise, a negative error value.

mango_pcc_ctrl_reg_algo​

mango_status_e mango_pcc_ctrl_reg_algo(mango_pcc_h pcc,
                                       unsigned int slot,
                                       mango_pcc_algo_fn *algo,
                                       const void *initial_params,
                                       size_t param_size)

Register a congestion control algorithm callback.

Parameters

  • in pcc The PCC handle.
  • in slot The slot index at which to register the algorithm.
  • in algo Pointer to the algorithm function to be invoked.
  • in initial_params Pointer to the algorithm parameters with the initial values.
  • in param_size The size of the parameter structure.

Returns 0 on success, Otherwise, a negative error value.

mango_pcc_ctrl_run​

mango_status_e mango_pcc_ctrl_run(mango_pcc_h pcc, unsigned int num_threads)

Start the PCC control loop with a given number of threads.

Parameters

  • in pcc The PCC handle.
  • in num_threads Number of poller threads to spawn.

Returns 0 on success, Otherwise, a negative error value.

mango_pcc_ctrl_stop​

mango_status_e mango_pcc_ctrl_stop(mango_pcc_h pcc)

Stop the PCC control loop.

Parameters

  • in pcc The PCC handle.

Returns 0 on success, Otherwise, a negative error value.

mango_pcc_window_current​

unsigned int mango_pcc_window_current()

Get the current PCC window size of the QP.

Returns The current window size.

mango_pcc_window_update​

void mango_pcc_window_update(unsigned int new_window)

Update the PCC window size of the QP.

Parameters

  • in new_window The new window size to set.

mango_pcc_event_cnp_cnt​

unsigned int mango_pcc_event_cnp_cnt()

Get the count of new congestion notification (CNP) events.

Returns The number of CNP events observed.

mango_pcc_log​

void mango_pcc_log(mango_log_level_e level, const char *fmt,...)

Print a log message with Poller index and QP number.

Parameters

  • in level The log level.
  • in fmt The format string.
note

The message will be ignore if the system log level is lower.