On 9/18/2020 4:44 AM, Jiang, JunyuX wrote:
Hi Ferruh,

-----Original Message-----
From: Ferruh Yigit <ferruh.yi...@intel.com>
Sent: Wednesday, September 16, 2020 8:31 PM
To: Jiang, JunyuX <junyux.ji...@intel.com>; dev@dpdk.org
Cc: Guo, Jia <jia....@intel.com>; Xing, Beilei <beilei.x...@intel.com>;
sta...@dpdk.org
Subject: Re: [dpdk-stable] [PATCH v2] net/i40e: fix incorrect byte counters

On 9/16/2020 2:51 AM, Junyu Jiang wrote:
This patch fixed the issue that rx/tx bytes overflowed

"Rx/Tx statistics counters overflowed"?

Yes, the rx_bytes and tx_bytes counter in X710 cards is 48-bit long, if keep 
sending packets for a log time, the register will overflow.

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>
---
   drivers/net/i40e/i40e_ethdev.c | 47
++++++++++++++++++++++++++++++++++
   drivers/net/i40e/i40e_ethdev.h |  9 +++++++
   2 files changed, 56 insertions(+)

diff --git a/drivers/net/i40e/i40e_ethdev.c
b/drivers/net/i40e/i40e_ethdev.c index 563f21d9d..4d4ea9861 100644
--- a/drivers/net/i40e/i40e_ethdev.c
+++ b/drivers/net/i40e/i40e_ethdev.c
@@ -3073,6 +3073,13 @@ i40e_update_vsi_stats(struct i40e_vsi *vsi)
        i40e_stat_update_48(hw, I40E_GLV_BPRCH(idx),
I40E_GLV_BPRCL(idx),
                            vsi->offset_loaded, &oes->rx_broadcast,
                            &nes->rx_broadcast);
+       /* enlarge the limitation when rx_bytes overflowed */
+       if (vsi->offset_loaded) {
+               if (I40E_RXTX_BYTES_LOW(vsi->old_rx_bytes) > nes-
rx_bytes)
+                       nes->rx_bytes += (uint64_t)1 << I40E_48_BIT_WIDTH;
+               nes->rx_bytes += I40E_RXTX_BYTES_HIGH(vsi-
old_rx_bytes);
+       }
+       vsi->old_rx_bytes = nes->rx_bytes;


Can you please describe this logic? (indeed better to describe it in the
commit log)

'nes->rx_bytes' is diff in the stats register since last read.
'old_rx_bytes' is the previous stats diff.

Why/how "I40E_RXTX_BYTES_LOW(vsi->old_rx_bytes) > nes->rx_bytes" has
a meaning? Isn't this very depends on the read frequency?

I guess I am missing something but please help me understand.

This patch fixes the issue of rx/tx bytes counter register overflow:
The counter register in i40e is 48-bit long, when overflow, nes->rx_bytes becomes less 
than old_rx_bytes, the correct value of nes->rx_bytes should be plused 1 << 48.
Use I40E_RXTX_BYTES_HIGH() to remember the MSB, nes->rx_bytes plus the MSB is 
the correct value, So that using uint64_t to enlarge the 48 bit  limitation of 
register .
>

My bad, 'nes->rx_bytes' is NOT diff in the stats register since last read, it is accumulated stats value since last reset. Above logic make sense now.

What do you think creating a function something like 'i40e_stat_update_48_in_64()' and hide all the extension inside it?
I think it reduces the clutter.


Also can you please confirm the initial value of the "vsi->offset_loaded" is
correct.

offset_loaded will be true when get statistics of  port and offset_loaded will 
be false when reset or clear the statistics,
so if  offset_loaded is false, shouldn't to calculate the value of 
nes->rx_bytes, it will be 0.

<....>

@@ -282,6 +282,9 @@ struct rte_flow {
   #define I40E_ETH_OVERHEAD \
        (RTE_ETHER_HDR_LEN + RTE_ETHER_CRC_LEN +
I40E_VLAN_TAG_SIZE * 2)

+#define I40E_RXTX_BYTES_HIGH(bytes) ((bytes) & ~I40E_48_BIT_MASK)
+#define I40E_RXTX_BYTES_LOW(bytes) ((bytes) & I40E_48_BIT_MASK)
+

HIGH/LOW is a little misleading, for 64Bits it sounds like it is getting low 32 
bits
and high 32 bits, can you please clarify macro masks out
48/16 bits.

Yes, I will change the macro name in V3.

   struct i40e_adapter;
   struct rte_pci_driver;

@@ -399,6 +402,8 @@ struct i40e_vsi {
        uint8_t vlan_anti_spoof_on; /* The VLAN anti-spoofing enabled */
        uint8_t vlan_filter_on; /* The VLAN filter enabled */
        struct i40e_bw_info bw_info; /* VSI bandwidth information */
+       uint64_t old_rx_bytes;
+       uint64_t old_tx_bytes;

'prev' seems better naming than 'old', what do you think renaming
'old_rx_bytes' -> 'prev_rx_bytes' (for all variables)?
Yes, it's better, I will fix it in V3.


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