Re: [PATCH] ixgbe: do not include CRC in Tx byte count

["Ananyev, Konstantin" <konstantin.ananyev-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

> -----Original Message-----
> From: dev [mailto:dev-bounces-VfR2kkLFssw@public.gmane.org] On Behalf Of stephen@networkplumber.org
> Sent: Friday, January 23, 2015 6:24 AM
> To: dev-VfR2kkLFssw@public.gmane.org
> Cc: Stephen Hemminger
> Subject: [dpdk-dev] [PATCH] ixgbe: do not include CRC in Tx byte count
> 
> From: Stephen Hemminger <shemming-43mecJUBy8ZBDgjK7y7TUQ@public.gmane.org>
> 
> The ixgbe driver was including CRC in the transmit packet byte
> count, but not for packets received.
> This was notice when forwarding and
> the number of bytes received was greater than the number of bytes transmitted
> for the same number of packets. Make the driver behave like other
> virtual devices and not include CRC in byte count. Use the same queue
> counters already computed and used for Rx.

About RX side stats - as I remember it depends to what value hw_stip_crc is set at configure().
If hw_stip_crc==1, then, yes CRC bytes are not included into  QBRC value.
I If hw_stip_crc==0, then CRC bytes are included into QBRC. 

I.E:
./dpdk.org/x86_64-native-linuxapp-gcc/app/testpmd -c ff -n 4 -w 86:00.1 -- -i --tx-queue-stats-mapping='(0,0,0)' --rx-queue-stats-mapping='(0,0,0)' --crc-strip
testpmd> start
testpmd> show port stats all

######################## NIC statistics for port 0  ########################
  RX-packets:                       1    RX-errors:          0    RX-bytes:         60       // sum of QBRC[]
  RX-badcrc:                        0    RX-badlen:          0  RX-errors:           0
  RX-nombuf:                        0
  TX-packets:                       1    TX-errors:          0    TX-bytes:         64  //GOTC

  Stats reg  0 RX-packets:          1    RX-errors:          0    RX-bytes:         60 //QBRC[0]
  ...

  Stats reg  0 TX-packets:          1                             TX-bytes:         60   // QBTC[0]
   ############################################################################


./dpdk.org/x86_64-native-linuxapp-gcc/app/testpmd -c ff -n 4 -w 86:00.1 -- -i --tx-queue-stats-mapping='(0,0,0)' --rx-queue-stats-mapping='(0,0,0)'
testpmd> start
testpmd> show port stats all

  ######################## NIC statistics for port 0  ########################
  RX-packets:                       1    RX-errors:          0    RX-bytes:         64  // sum of QBRC[]
  RX-badcrc:                        0    RX-badlen:          0  RX-errors:           0
  RX-nombuf:                        0
  TX-packets:                       1    TX-errors:          0    TX-bytes:         64  //GOTC

  Stats reg  0 RX-packets:          1    RX-errors:          0    RX-bytes:         64 //QBRC[0]
  ....

  Stats reg  0 TX-packets:          1                             TX-bytes:         60  // QBTC[0]
    ############################################################################

So now, number of RX/TX stat bytes for simple forwarding are equal when hw_stip_crc==0 and
differ when hw_stip_crc==1,
With your change, as I understand, it would be visa-versa.
I don' t mind changing it yours way, but wonder why that is any better?
Probably the proper patch, should also do something like that:
stats->ibytes = total_qbrc - stats->ipackets  * dev->data->dev_conf. hw_strip_crc * CRC_LEN;
too? 

About using sum of QBRC[] for stats.ibytes instead of GORC, I think the initial reason was:

http://www.intel.com/content/www/us/en/ethernet-controllers/82599-10-gbe-controller-spec-update.html:
7 GPRC and GORCL/H Also Count Missed Packets
Problem:
GPRC (Good Packets Received Count) and GORCL/H (Good Octets Received Count) count missed
packets and missed packets bytes; this is not consistent with previous products.
Implication:
None.
331521-002 23
Errata-Intel(r) 82599 10 GbE Controller
Workaround:
Statistics are available indirectly for these registers. This workaround is included in Intel drivers.
* For GPRC - Subtract MPC (Missed Packet Count) from GPRC. Alternatively, use QPRC.
* For GORCL/H - use QBRCL/H (Quad Bytes Received).

Konstantin

> 
> Signed-off-by: Stephen Hemminger <stephen-OTpzqLSitTUnbdJkjeBofR2eb7JE58TQ@public.gmane.org>
> ---
>  lib/librte_pmd_ixgbe/ixgbe_ethdev.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/librte_pmd_ixgbe/ixgbe_ethdev.c b/lib/librte_pmd_ixgbe/ixgbe_ethdev.c
> index b58ec45..27355eb 100644
> --- a/lib/librte_pmd_ixgbe/ixgbe_ethdev.c
> +++ b/lib/librte_pmd_ixgbe/ixgbe_ethdev.c
> @@ -1724,12 +1724,15 @@ ixgbe_dev_stats_get(struct rte_eth_dev *dev, struct rte_eth_stats *stats)
>  	struct ixgbe_hw_stats *hw_stats =
>  			IXGBE_DEV_PRIVATE_TO_STATS(dev->data->dev_private);
>  	uint32_t bprc, lxon, lxoff, total;
> -	uint64_t total_missed_rx, total_qbrc, total_qprc;
> +	uint64_t total_missed_rx;
> +	uint64_t total_qbrc, total_qprc, total_qbtc, total_qptc;
>  	unsigned i;
> 
>  	total_missed_rx = 0;
>  	total_qbrc = 0;
>  	total_qprc = 0;
> +	total_qbtc = 0;
> +	total_qptc = 0;
> 
>  	hw_stats->crcerrs += IXGBE_READ_REG(hw, IXGBE_CRCERRS);
>  	hw_stats->illerrc += IXGBE_READ_REG(hw, IXGBE_ILLERRC);
> @@ -1770,6 +1773,8 @@ ixgbe_dev_stats_get(struct rte_eth_dev *dev, struct rte_eth_stats *stats)
> 
>  		total_qprc += hw_stats->qprc[i];
>  		total_qbrc += hw_stats->qbrc[i];
> +		total_qptc += hw_stats->qptc[i];
> +		total_qbtc += hw_stats->qbtc[i];
>  	}
>  	hw_stats->mlfc += IXGBE_READ_REG(hw, IXGBE_MLFC);
>  	hw_stats->mrfc += IXGBE_READ_REG(hw, IXGBE_MRFC);
> @@ -1860,8 +1865,8 @@ ixgbe_dev_stats_get(struct rte_eth_dev *dev, struct rte_eth_stats *stats)
>  	/* Fill out the rte_eth_stats statistics structure */
>  	stats->ipackets = total_qprc;
>  	stats->ibytes = total_qbrc;
> -	stats->opackets = hw_stats->gptc;
> -	stats->obytes = hw_stats->gotc;
> +	stats->opackets = total_qptc;
> +	stats->obytes = total_qbtc;
>  	stats->imcasts = hw_stats->mprc;
> 
>  	for (i = 0; i < IXGBE_QUEUE_STAT_COUNTERS; i++) {
> --
> 2.1.4