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References: <9279c2f3-195c-0034-48e6-4246eee428a9@altencalsoftlabs.com>
To: users@dpdk.org
From: Sharon <sharon.t@altencalsoftlabs.com>
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Subject: [dpdk-users] Tx burst getting failed with Virtio driver
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Hi,


With a dpdk based application inside GCP VM instance,
it is observed that while sending UDP packets of length 1300 at around 6=20
Gbps rate, tx burst starts failing frequently.

On enabling virtio pmd logs, following error is found:

PMD: virtio_xmit_pkts() tx: No free tx descriptors to transmit

*VM configuration:*

Cores: Total 12 cores, 5 cores for the application
OS: CentOS 7.2.1511
Linux kernel : 3.10.0-327.13.1.el7.x86_64
DPDK version : 17.05*
*

*Ring configuration in application:*

TX descriptor ring size: 4096
RX descriptor ring size: 1024
4 cores for rx and tx in a run to completion model.
Single port is used for Rx and Tx.
lcore to queue mapping is 1:1, i.e 1rx queue and 1tx queue per lcore

*ethtool -g eth0*
Ring parameters for eth0:
Pre-set maximums:
RX:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
 4096
RX Mini:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 0
RX Jumbo:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 0
TX:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
 4096
Current hardware settings:
RX:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
 4096
RX Mini:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 =C2=A0 =C2=A0 0
RX Jumbo:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 0
TX:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
 4096

*lscpu*

Architecture:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0 x86_64
CPU op-mode(s): =C2=A0 =C2=A0=C2=A0 32-bit, 64-bit
Byte Order:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0 Little Endian
CPU(s):=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 12
On-line CPU(s) list:=C2=A0=C2=A0=C2=A0 0-11
Thread(s) per core:=C2=A0 2
Core(s) per socket:=C2=A0=C2=A0 6
Socket(s):=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 1
NUMA node(s):=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 1
Vendor ID: =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 GenuineIntel
CPU family:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0 6
Model:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 85
Model name:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 I=
ntel(R) Xeon(R) CPU @ 2.00GHz
Stepping:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 3
CPU MHz:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0 2000.168
BogoMIPS:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0 4000.33
Hypervisor vendor: KVM
Virtualization type:=C2=A0 full
L1d cache:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0 32K
L1i cache:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0=C2=A0=C2=A0 32K
L2 cache:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0 256K
L3 cache:=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0 56320K
NUMA node0 CPU(s): 0-11

*NIC stats is provided below:*

100330695 packets input, 141154589263 bytes
100310198 packets output, 136450396190 bytes
0 packets missed
0 erroneous packets received
0 multicast packets received
0 failed transmitted packets
0 No Mbufs


Stats reg 0 RX-packets: 23454090 RX-errors: 0 RX-bytes: 32948589715
Stats reg 1 RX-packets: 23954850 RX-errors: 0 RX-bytes: 33699067521
Stats reg 2 RX-packets: 26014919 RX-errors: 0 RX-bytes: 36614183404
Stats reg 3 RX-packets: 26906836 RX-errors: 0 RX-bytes: 37892748623


Stats reg 0 TX-packets: 23450529 TX-bytes: 31934107195
Stats reg 1 TX-packets: 23951340 TX-bytes: 32591951998
Stats reg 2 TX-packets: 26008018 TX-bytes: 35366748482
Stats reg 3 TX-packets: 26900311 TX-bytes: 36557588515

Increasing the number of cores for the application is also not helping=20
in this case.

Kindly suggest as what needs to be done to improve the performance and=20
avoid this issue.

Thanks & Regards,
Sharon T N