Re: [dpdk-dev] How can I calculate/estimate pps(packet per seocond) and bps(bit per second) in DPDK pktg

["Wiles, Keith" <keith.wiles@intel.com>]

On 11/3/15, 9:59 AM, "Polehn, Mike A" <mike.a.polehn@intel.com> wrote:

>I used the following code snip-it with the i40e device, with 1 second sample time had very high accuracy for IPv4 UDP packets:
>
>#define FLOWD_PERF_PACKET_OVERHEAD 24  /* CRC + Preamble + SOF + Interpacket gap */
>#define FLOWD_REF_NETWORK_SPEED   10e9
>
>double Ave_Bytes_per_Packet, Data_Rate, Net_Rate;
>uint64_t Bits;
>uint64_t Bytes = pFlow->flow.n_bytes - pMatch_Prev->flow.n_bytes;
>uint64_t Packets = pFlow->flow.n_packets - pMatch_Prev->flow.n_packets;
>uint64_t Time_us = pFlow->flow.flow_time_us - pMatch_Prev->flow.flow_time_us;
>
>if (Bytes == 0)
>	Ave_Bytes_per_Packet = 0.0;
>else
>	Ave_Bytes_per_Packet = ((double)Bytes / (double)Packets) + 4.0;
>
>Bits = (Bytes + (Packets*FLOWD_PERF_PACKET_OVERHEAD)) * 8;
>if (Bits == 0)
>	Data_Rate = 0.0;
>else
>	Data_Rate = (((double)Bits) / Time_us) * 1e6;
>
>if (Data_Rate == 0.0)
>	Net_Rate = 0.0;
>else
>	Net_Rate = Data_Rate / FLOWD_REF_NETWORK_SPEED;
>
>For packet rate: double pk_rate = (((double)Packets)/ ((double)Time_us)) * 1e6;
>
>To calculate elapsed time in DPDK app, used CPU counter (will not work if counter is being modified):
>
>Initialization:
>double flow_time_scale_us;
>...
>flow_time_scale_us = 1e6/rte_get_tsc_hz();
>
>Elapsed time (uSec) example: 
>
>elapse_us = (rte_rdtsc() - entry->tsc_first_packet) *
>	flow_time_scale_us; /* calc total elapsed us */

Looks reasonable I assume the n_bytes does not include FCS as is not the case with the NIC counters.

Also I decided to avoid using double’s in my code and just used 64bit registers and integer math :-) 

>
>-----Original Message-----
>From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Wiles, Keith
>Sent: Tuesday, November 3, 2015 6:33 AM
>To: Van Haaren, Harry; ???; dev@dpdk.org
>Subject: Re: [dpdk-dev] How can I calculate/estimate pps(packet per seocond) and bps(bit per second) in DPDK pktg
>
>On 11/3/15, 8:30 AM, "Van Haaren, Harry" <harry.van.haaren@intel.com> wrote:
>
>>Hi Keith,
>>
>>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Wiles, Keith
>><snip>
>>> Hmm, I just noticed I did not include the FCS bytes. Does the NIC 
>>> include FCS bytes in the counters? Need to verify that one and if not then it becomes a bit more complex.
>>
>>The Intel NICs count packet sizes inclusive of CRC / FCS, from eg the ixgbe/82599 datasheet:
>>"This register includes bytes received in a packet from the <Destination Address> field through the <CRC> field, inclusively."
>
>Thanks I assumed I had known that at the time :-)
>>
>>-Harry
>>
>
>
>Regards,
>Keith
>
>
>
>
>


Regards,
Keith