On 9/21/2020 10:59 AM, Junyu Jiang wrote:
This patch fixed the issue that rx/tx bytes statistics counters
overflowed on 48 bit limitation by enlarging the limitation.

Fixes: 4861cde46116 ("i40e: new poll mode driver")
Cc: sta...@dpdk.org

Signed-off-by: Junyu Jiang <junyux.ji...@intel.com>
---
  doc/guides/nics/i40e.rst       |  7 +++++++
  drivers/net/i40e/i40e_ethdev.c | 32 ++++++++++++++++++++++++++++++++
  drivers/net/i40e/i40e_ethdev.h |  9 +++++++++
  3 files changed, 48 insertions(+)

diff --git a/doc/guides/nics/i40e.rst b/doc/guides/nics/i40e.rst
index b7430f6c4..4baa58be6 100644
--- a/doc/guides/nics/i40e.rst
+++ b/doc/guides/nics/i40e.rst
@@ -830,3 +830,10 @@ Tx bytes affected by the link status change
For firmware versions prior to 6.01 for X710 series and 3.33 for X722 series, the tx_bytes statistics data is affected by
  the link down event. Each time the link status changes to down, the tx_bytes 
decreases 110 bytes.
+
+RX/TX statistics may be incorrect when register overflowed
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The rx_bytes/tx_bytes statistics register is 48 bit length. Although this 
limitation is enlarged to 64 bit length
+on the software side, but there is no way to detect if the overflow occurred 
more than once. So rx_bytes/tx_bytes
+statistics data is correct when statistics are updated at least once between 
two overflows.
diff --git a/drivers/net/i40e/i40e_ethdev.c b/drivers/net/i40e/i40e_ethdev.c
index 563f21d9d..212338ef0 100644
--- a/drivers/net/i40e/i40e_ethdev.c
+++ b/drivers/net/i40e/i40e_ethdev.c
@@ -3052,6 +3052,19 @@ i40e_dev_link_update(struct rte_eth_dev *dev,
        return ret;
  }
+static void
+i40e_stat_update_48_in_64(uint64_t *new_bytes,
+                         uint64_t *prev_bytes,
+                         bool offset_loaded)
+{
+       if (offset_loaded) {
+               if (I40E_RXTX_BYTES_L_48_BIT(*prev_bytes) > *new_bytes)
+                       *new_bytes += (uint64_t)1 << I40E_48_BIT_WIDTH;
+               *new_bytes += I40E_RXTX_BYTES_H_16_BIT(*prev_bytes);
+       }
+       *prev_bytes = *new_bytes;
+}
+

I was more thinking reading stats and extending in same function, instead of extracting the extending part into its own function, like:

static void
i40e_stat_update_48_in_64(struct i40e_hw *hw,
                uint32_t hireg,
                uint32_t loreg,
                bool offset_loaded,
                uint64_t *offset,
                uint64_t *stat,
                uint64_t *prev_bytes) {

        i40e_stat_update_48(...)

        /* logic to convert 'stat' to 64 bits */
}

Does it make sense?

Reply via email to