That's an interesting theory, you could add a check into the tx path looking for a zero m_len and see, seems unlikely though :)
Jack On Fri, Jun 3, 2016 at 1:15 PM, Sreekanth Rupavatharam <[email protected] > wrote: > Wondering if this can happen if somehow the mbuf->m_len is not > correct(e.g., 0) and thus causing the dma to fail silently. The only way > this is happening if the arp request is larger than 64 bytes and the arp > response code is reusing the packet to send a 64 byte response. > > Thanks, > > -Sreekanth > > > On 6/2/16, 2:41 PM, "hiren panchasara" <[email protected]> wrote: > > >+ Sean, Eric > > > >On 06/02/16 at 09:11P, Sreekanth Rupavatharam wrote: > >> Inline > >> > >> >Apart from stats, do you see anything else going wrong? i.e. do you > >> >actually see less packets (arp replies??) than expected? > >> > >> [SR] The packets are not going out on the wire. The tool doesn?t > receive the packets. That?s how I started noticing the issue. > >> > >> >Taking your example, tx_packets is something we count in the drivers > and > >> >total_pkts_txd is calculated in the card and we just read it off of it > >> >to report (E1000_TPT). > >> > >> [SR] Correct. My main question would be under what circumstance would > the packet handed off to hardware will *not* be transmitted?. Especially > considering there are no transmit errors or pause frames received. There > are no dma tx failures either. That?s the baffling part. I tried another > exercise where I used ping of various sizes going out, but that doesn?t > seem to trigger the problem. > >> > >> > >> >To understand your setup better, ixia is the sender and your box with > >> >igb(4) is the receiver and your are sending arp requests to it. > >> > >> Yes, correct. > >> > >> >Can you post following for working (size <= 64bytes) and non-working > >> >(size > 64bytes) cases for before/after? > >> > > >> >sysctl dev.igb | grep tx_packets > >> >sysctl dev.igb | grep total_pkts_txd > >> >sysctl dev.igb | grep rx_packets > >> >sysctl dev.igb | grep total_pkts_recvd > >> > >> > >> Before(not working): > >> dev.igb.1.queue0.tx_packets: 24907933 > >> dev.igb.1.queue0.rx_packets: 18086575 > >> dev.igb.1.mac_stats.total_pkts_recvd: 25057359 > >> dev.igb.1.mac_stats.total_pkts_txd: 16647169 > >> > >> After(not working): > >> dev.igb.1.queue0.tx_packets: 24913324 > >> dev.igb.1.queue0.rx_packets: 18091832 > >> dev.igb.1.mac_stats.total_pkts_recvd: 25062618 > >> dev.igb.1.mac_stats.total_pkts_txd: 16647545 > >> >netstat -sp arp > >> > >> The difference is 5391 for queue0.tx_packets but for > mac_stats.total_pkts_txd is 376 > >> Everything else is matching up. > >> > >> Before (working) > >> dev.igb.1.queue0.tx_packets: 25359165 > >> dev.igb.1.queue0.rx_packets: 18526094 > >> dev.igb.1.mac_stats.total_pkts_recvd: 25508763 > >> dev.igb.1.mac_stats.total_pkts_txd: 16831587 > >> > >> > >> After(working) > >> dev.igb.1.queue0.tx_packets: 25364597 > >> dev.igb.1.queue0.rx_packets: 18531398 > >> dev.igb.1.mac_stats.total_pkts_recvd: 25514009 > >> dev.igb.1.mac_stats.total_pkts_txd: 16836833 > >> > >> > >> Another interesting stat is > >> before_notworking:dev.igb.1.interrupts.tx_queue_empty: 16646890 > >> after_notworking:dev.igb.1.interrupts.tx_queue_empty: 16647266 > >> > >> The difference here is exactly 376 which is the number of packets that > the device actually claims to have transmitted. It?s as though it didn?t > see the other packets en-queued in the ring descriptor. > >> > > > >Very interesting. Do you tune defaults at all? What does sysctl hw.igb > >say? Not sure if bumping up txd would help. > > > >Adding Sean and Eric to throw some light. > > > >> > >> I can?t do netstat just for arp as these are coming in a tunnel(Packets > don?t? show up as arp on the interface). However, I did see the packet rate > was about 500 packets/sec > >> > > > >Cheers, > >Hiren > > _______________________________________________ [email protected] mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "[email protected]"
