Re: [RFC PATCH 0/4] Implement multiqueue virtio-net

Krishna Kumar2
2010-09-08T12:17:40Z

"Michael S. Tsirkin" <mst@redhat.com> wrote on 09/08/2010 04:18:33 PM:

>
_______________________________________________________________________________

> >
> > > > TCP (#numtxqs=2)
> > > > N# BW1 BW2 (%) SD1 SD2 (%) RSD1
RSD2
> > (%)
> > > >
> > >
> >
>
_______________________________________________________________________________

> >
> > > > 4 26387 40716 (54.30) 20 28 (40.00) 86i 85
> > (-1.16)
> > > > 8 24356 41843 (71.79) 88 129 (46.59) 372 362
> > (-2.68)
> > > > 16 23587 40546 (71.89) 375 564 (50.40) 1558
1519
> > (-2.50)
> > > > 32 22927 39490 (72.24) 1617 2171 (34.26) 6694
5722
> > (-14.52)
> > > > 48 23067 39238 (70.10) 3931 5170 (31.51) 15823
13552
> > (-14.35)
> > > > 64 22927 38750 (69.01) 7142 9914 (38.81) 28972
26173
> > (-9.66)
> > > > 96 22568 38520 (70.68) 16258 27844 (71.26) 65944
73031
> > (10.74)
> > >
> > > That's a significant hit in TCP SD. Is it caused by the imbalance
between
> > > number of queues for TX and RX? Since you mention RX is complete,
> > > maybe measure with a balanced TX/RX?
> >
> > Yes, I am not sure why it is so high.
>
> Any errors at higher levels? Are any packets reordered?

I haven't seen any messages logged, and retransmission is similar
to non-mq case. Device also has no errors/dropped packets. Anything
else I should look for?

On the host:

# ifconfig vnet0
vnet0 Link encap:Ethernet HWaddr 9A:9D:99:E1:CA:CE
inet6 addr: fe80::989d:99ff:fee1:cace/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:5090371 errors:0 dropped:0 overruns:0 frame:0
TX packets:5054616 errors:0 dropped:0 overruns:65 carrier:0
collisions:0 txqueuelen:500
RX bytes:237793761392 (221.4 GiB) TX bytes:333630070 (318.1 MiB)
# netstat -s |grep -i retrans
1310 segments retransmited
35 times recovered from packet loss due to fast retransmit
1 timeouts after reno fast retransmit
41 fast retransmits
1236 retransmits in slow start

So retranmissions are 0.025% of total packets received from the guest.

Thanks,

- KK