About batch mechanism in Bess

[btlcmr0702]

Hi I wonder when will the receiver get a batch of packets(batch->cnt() > 1) instead of just one packet(batch->cnt() =1)? And what will influence the value of cnt of batch? Expected your reply. Thanks a lot

[sangjinhan]

(I am sorry for this late response)

You can/should assume that the batch will contain more than 1 packet. For example, suppose your NIC port receives packets at 100kpps, but it is polled by BESS only at 20k/s for some reason. Then we can expect the average batch size will be 5 packets / batch. In general, the polling rate of a TC will be low (thus batch size becomes larger) when:

• Input load is high
• CPU is slow
• There are many modules and/or each module is expensive
• There are many other traffic classes
• The TC is rate-limited