On 14/09/2021 02:31, Alvin Zhang wrote:
> This patch adds a devarg parameter to enable/disable reducing the
> Rx latency.
>
> Signed-off-by: Alvin Zhang <alvinx.zh...@intel.com>
> ---
> doc/guides/nics/ice.rst | 8 ++++++++
> drivers/net/ice/ice_ethdev.c | 26 +++++++++++++++++++++++---
> drivers/net/ice/ice_ethdev.h | 1 +
> 3 files changed, 32 insertions(+), 3 deletions(-)
>
> diff --git a/doc/guides/nics/ice.rst b/doc/guides/nics/ice.rst
> index 5bc472f..3db0430 100644
> --- a/doc/guides/nics/ice.rst
> +++ b/doc/guides/nics/ice.rst
> @@ -219,6 +219,14 @@ Runtime Config Options
>
> These ICE_DBG_XXX are defined in ``drivers/net/ice/base/ice_type.h``.
>
> +- ``Reduce Rx interrupts and latency`` (default ``0``)
> +
> + vRAN workloads require low latency DPDK interface for the front haul
> + interface connection to Radio. Now we can reduce Rx interrupts and
> + latency by specify ``1`` for parameter ``rx-low-latency``::
> +
> + -a 0000:88:00.0,rx-low-latency=1
> +
When would a user select this and when not? What is the trade off?
The text is a bit unclear. It looks below like it reduces the interrupt
latency, but not the number of interrupts. Maybe I got it wrong.
> Driver compilation and testing
> ------------------------------
>
> diff --git a/drivers/net/ice/ice_ethdev.c b/drivers/net/ice/ice_ethdev.c
> index a4cd39c..85662e4 100644
> --- a/drivers/net/ice/ice_ethdev.c
> +++ b/drivers/net/ice/ice_ethdev.c
> @@ -29,12 +29,14 @@
> #define ICE_PIPELINE_MODE_SUPPORT_ARG "pipeline-mode-support"
> #define ICE_PROTO_XTR_ARG "proto_xtr"
> #define ICE_HW_DEBUG_MASK_ARG "hw_debug_mask"
> +#define ICE_RX_LOW_LATENCY "rx-low-latency"
>
> static const char * const ice_valid_args[] = {
> ICE_SAFE_MODE_SUPPORT_ARG,
> ICE_PIPELINE_MODE_SUPPORT_ARG,
> ICE_PROTO_XTR_ARG,
> ICE_HW_DEBUG_MASK_ARG,
> + ICE_RX_LOW_LATENCY,
> NULL
> };
>
> @@ -1827,6 +1829,9 @@ static int ice_parse_devargs(struct rte_eth_dev *dev)
> if (ret)
> goto bail;
>
> + ret = rte_kvargs_process(kvlist, ICE_RX_LOW_LATENCY,
> + &parse_bool, &ad->devargs.rx_low_latency);
> +
> bail:
> rte_kvargs_free(kvlist);
> return ret;
> @@ -3144,8 +3149,9 @@ static int ice_init_rss(struct ice_pf *pf)
> {
> 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) |
> @@ -3155,8 +3161,21 @@ static int ice_init_rss(struct ice_pf *pf)
>
> 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);
Why not set this to 0? "Setting the INTERVAL to zero enables
immediate interrupt."
> + 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);
> }
> @@ -5314,7 +5333,8 @@ static int ice_xstats_get_names(__rte_unused struct
> rte_eth_dev *dev,
> 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 "=<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 b4bf651..c61cc1f 100644
> --- a/drivers/net/ice/ice_ethdev.h
> +++ b/drivers/net/ice/ice_ethdev.h
> @@ -463,6 +463,7 @@ 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;
>
