On 18/09/2021 02:33, Zhang, AlvinX wrote:
-----Original Message-----
From: Kevin Traynor <ktray...@redhat.com>
Sent: Saturday, September 18, 2021 1:25 AM
To: Zhang, AlvinX <alvinx.zh...@intel.com>; Zhang, Qi Z
<qi.z.zh...@intel.com>; Guo, Junfeng <junfeng....@intel.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH] net/ice: add ability to reduce the Rx latency
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.
Yes, it reduces the interrupt latency,
We will refine the doc in next patch.
Thanks, the text in v2 is clearer.
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."
Didn't see a reply to this comment?
I'm not requesting a change, just asking if there is a reason you didn't
choose the lowest latency setting, and if you should?
+ 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;
