net/ice: support low Rx latency

This patch adds a devarg parameter to enable/disable low Rx latency.

Signed-off-by: Alvin Zhang <alvinx.zhang@intel.com>
Acked-by: Qi Zhang <qi.z.zhang@intel.com>

diff --git a/doc/guides/nics/ice.rst b/doc/guides/nics/ice.rst
index ebe2cbc..8d43488 100644 (file)
--- a/doc/guides/nics/ice.rst
+++ b/doc/guides/nics/ice.rst
@@ -227,6 +227,18 @@ Runtime Config Options
 
     -a af:00.0,pps_out='[pin:0]'
 
+- ``Low Rx latency`` (default ``0``)
+
+  vRAN workloads require low latency DPDK interface for the front haul
+  interface connection to Radio. By specifying ``1`` for parameter
+  ``rx_low_latency``, each completed Rx descriptor can be written immediately
+  to host memory and the Rx interrupt latency can be reduced to 2us::
+
+    -a 0000:88:00.0,rx_low_latency=1
+
+  As a trade-off, this configuration may cause the packet processing performance
+  degradation due to the PCI bandwidth limitation.
+
 Driver compilation and testing
 ------------------------------
 

diff --git a/drivers/net/ice/ice_ethdev.c b/drivers/net/ice/ice_ethdev.c
index 66e33a1..d264090 100644 (file)
--- a/drivers/net/ice/ice_ethdev.c
+++ b/drivers/net/ice/ice_ethdev.c
@@ -30,6 +30,7 @@
 #define ICE_PROTO_XTR_ARG         "proto_xtr"
 #define ICE_HW_DEBUG_MASK_ARG     "hw_debug_mask"
 #define ICE_ONE_PPS_OUT_ARG       "pps_out"
+#define ICE_RX_LOW_LATENCY_ARG    "rx_low_latency"
 
 static const char * const ice_valid_args[] = {
        ICE_SAFE_MODE_SUPPORT_ARG,
@@ -37,6 +38,7 @@ static const char * const ice_valid_args[] = {
        ICE_PROTO_XTR_ARG,
        ICE_HW_DEBUG_MASK_ARG,
        ICE_ONE_PPS_OUT_ARG,
+       ICE_RX_LOW_LATENCY_ARG,
        NULL
 };
 
@@ -1956,6 +1958,9 @@ static int ice_parse_devargs(struct rte_eth_dev *dev)
        if (ret)
                goto bail;
 
+       ret = rte_kvargs_process(kvlist, ICE_RX_LOW_LATENCY_ARG,
+                                &parse_bool, &ad->devargs.rx_low_latency);
+
 bail:
        rte_kvargs_free(kvlist);
        return ret;
@@ -3272,8 +3277,9 @@ __vsi_queues_bind_intr(struct ice_vsi *vsi, uint16_t msix_vect,
 {
        struct ice_hw *hw = ICE_VSI_TO_HW(vsi);
        uint32_t val, val_tx;
-       int i;
+       int rx_low_latency, i;
 
+       rx_low_latency = vsi->adapter->devargs.rx_low_latency;
        for (i = 0; i < nb_queue; i++) {
                /*do actual bind*/
                val = (msix_vect & QINT_RQCTL_MSIX_INDX_M) |
@@ -3283,8 +3289,21 @@ __vsi_queues_bind_intr(struct ice_vsi *vsi, uint16_t msix_vect,
 
                PMD_DRV_LOG(INFO, "queue %d is binding to vect %d",
                            base_queue + i, msix_vect);
+
                /* set ITR0 value */
-               ICE_WRITE_REG(hw, GLINT_ITR(0, msix_vect), 0x2);
+               if (rx_low_latency) {
+                       /**
+                        * Empirical configuration for optimal real time
+                        * latency reduced interrupt throttling to 2us
+                        */
+                       ICE_WRITE_REG(hw, GLINT_ITR(0, msix_vect), 0x1);
+                       ICE_WRITE_REG(hw, QRX_ITR(base_queue + i),
+                                     QRX_ITR_NO_EXPR_M);
+               } else {
+                       ICE_WRITE_REG(hw, GLINT_ITR(0, msix_vect), 0x2);
+                       ICE_WRITE_REG(hw, QRX_ITR(base_queue + i), 0);
+               }
+
                ICE_WRITE_REG(hw, QINT_RQCTL(base_queue + i), val);
                ICE_WRITE_REG(hw, QINT_TQCTL(base_queue + i), val_tx);
        }
@@ -5497,7 +5516,8 @@ RTE_PMD_REGISTER_PARAM_STRING(net_ice,
                              ICE_HW_DEBUG_MASK_ARG "=0xXXX"
                              ICE_PROTO_XTR_ARG "=[queue:]<vlan|ipv4|ipv6|ipv6_flow|tcp|ip_offset>"
                              ICE_SAFE_MODE_SUPPORT_ARG "=<0|1>"
-                             ICE_PIPELINE_MODE_SUPPORT_ARG "=<0|1>");
+                             ICE_PIPELINE_MODE_SUPPORT_ARG "=<0|1>"
+                             ICE_RX_LOW_LATENCY_ARG "=<0|1>");
 
 RTE_LOG_REGISTER_SUFFIX(ice_logtype_init, init, NOTICE);
 RTE_LOG_REGISTER_SUFFIX(ice_logtype_driver, driver, NOTICE);

diff --git a/drivers/net/ice/ice_ethdev.h b/drivers/net/ice/ice_ethdev.h
index ea9d892..26f5c56 100644 (file)
--- a/drivers/net/ice/ice_ethdev.h
+++ b/drivers/net/ice/ice_ethdev.h
@@ -476,6 +476,7 @@ struct ice_pf {
  * Cache devargs parse result.
  */
 struct ice_devargs {
+       int rx_low_latency;
        int safe_mode_support;
        uint8_t proto_xtr_dflt;
        int pipe_mode_support;