On 10/20/06, John Heffner <jheffner@xxxxxxx> wrote:
H.K. Jerry Chu wrote:
> Thanks for the prompt reply. There is no pkt loss, none, at either
> netem, pfifo_fast. or TCP level (from netstat -s -t). This is a back2back
> 1GbE link with one iperf test running.
What happens if you increase the local interface queue?
ip link set ethX txqueuelen 10000
It doesn't make any difference. But like I said before i've verified
there is no drop from netem, pfifo (tc -s qdisc) or TCP.
Overflowing the interface queue doesn't result in packet loss, but has
the same effect from a congestion control point of view.
Yes I know.
For the 150ms delay case, tcptrace shows the TCP receive window
never grows beyond ~15.5MB. That probably explains partly the
low (~615Mbps) throughput.
The receive window size sounds about right, given a 20 MB max receive
buffer. (1/4 is reserved for overhead.) However, I calculate a rate of
about 800 Mbps.
So I increased tcp_r/wmem[2] to 30MB from 20MB and throughput
does improve to ~800Mbps.
Then I discovered this is a sender side only problem as well, just
like the 100ms case. If I specify -w 20m to iperf on the xmit side
ONLY, throughput hit ~945Mbps.
Thanks for the prompt reply. There is no pkt loss, none, at either
netem, pfifo_fast. or TCP level (from netstat -s -t). This is a back2back
1GbE link with one iperf test running.
What's the output of tcptrace -rlW?
Note that window scaler = 9 so you'll have to multiple max win adv,
e.g., by 512. Also the data is collected on the xmit side below
netem so I'm not sure how useful it is.
Ostermann's tcptrace -- version 6.6.7 -- Thu Nov 4, 2004
1106596 packets seen, 1106596 TCP packets traced
elapsed wallclock time: 0:00:01.572130, 703883 pkts/sec analyzed
trace file elapsed time: 0:00:12.485334
TCP connection info:
1 TCP connection traced:
TCP connection 1:
host a: 192.168.192.22:5001
host b: 192.168.192.21:40915
complete conn: no (SYNs: 0) (FINs: 0)
first packet: Fri Oct 20 17:27:31.063400 2006
last packet: Fri Oct 20 17:27:43.548735 2006
elapsed time: 0:00:12.485334
total packets: 1106596
filename: out1
a->b: b->a:
total packets: 369017 total packets: 737579
ack pkts sent: 369017 ack pkts sent: 737579
pure acks sent: 369017 pure acks sent: 0
sack pkts sent: 0 sack pkts sent: 0
dsack pkts sent: 0 dsack pkts sent: 0
max sack blks/ack: 0 max sack blks/ack: 0
unique bytes sent: 0 unique bytes sent: 1067949432
actual data pkts: 0 actual data pkts: 737579
actual data bytes: 0 actual data bytes: 1067949432
rexmt data pkts: 0 rexmt data pkts: 0
rexmt data bytes: 0 rexmt data bytes: 0
zwnd probe pkts: 0 zwnd probe pkts: 0
zwnd probe bytes: 0 zwnd probe bytes: 0
outoforder pkts: 0 outoforder pkts: 0
pushed data pkts: 0 pushed data pkts: 760
SYN/FIN pkts sent: 0/0 SYN/FIN pkts sent: 0/0
req 1323 ws/ts: N/Y req 1323 ws/ts: N/Y
urgent data pkts: 0 pkts urgent data pkts: 0 pkts
urgent data bytes: 0 bytes urgent data bytes: 0 bytes
mss requested: 0 bytes mss requested: 0 bytes
max segm size: 0 bytes max segm size: 1448 bytes
min segm size: 0 bytes min segm size: 8 bytes
avg segm size: 0 bytes avg segm size: 1447 bytes
max win adv: 42773 bytes max win adv: 12 bytes
min win adv: 42773 bytes min win adv: 12 bytes
zero win adv: 0 times zero win adv: 0 times
avg win adv: 42773 bytes avg win adv: 12 bytes
max owin: 1 bytes max owin: 728345 bytes
min non-zero owin: 1 bytes min non-zero owin: 665 bytes
avg owin: 0 bytes avg owin: 355090 bytes
wavg owin: 0 bytes wavg owin: 252813 bytes
initial window: 0 bytes initial window: 0 bytes
initial window: 0 pkts initial window: 0 pkts
ttl stream length: NA ttl stream length: NA
missed data: NA missed data: NA
truncated data: 0 bytes truncated data: 1045822096 bytes
truncated packets: 0 pkts truncated packets: 737576 pkts
data xmit time: 0.000 secs data xmit time: 12.485 secs
idletime max: 28.6 ms idletime max: 34.3 ms
throughput: 0 Bps throughput: 85536306 Bps
RTT samples: 0 RTT samples: 368516
RTT min: 0.0 ms RTT min: 0.1 ms
RTT max: 0.0 ms RTT max: 6.6 ms
RTT avg: 0.0 ms RTT avg: 3.0 ms
RTT stdev: 0.0 ms RTT stdev: 2.2 ms
RTT from 3WHS: 0.0 ms RTT from 3WHS: 0.0 ms
RTT full_sz smpls: 0 RTT full_sz smpls: 368453
RTT full_sz min: 0.0 ms RTT full_sz min: 0.1 ms
RTT full_sz max: 0.0 ms RTT full_sz max: 6.6 ms
RTT full_sz avg: 0.0 ms RTT full_sz avg: 3.0 ms
RTT full_sz stdev: 0.0 ms RTT full_sz stdev: 2.2 ms
post-loss acks: 0 post-loss acks: 275
segs cum acked: 0 segs cum acked: 368779
duplicate acks: 0 duplicate acks: 0
triple dupacks: 0 triple dupacks: 0
max # retrans: 0 max # retrans: 0
min retr time: 0.0 ms min retr time: 0.0 ms
max retr time: 0.0 ms max retr time: 0.0 ms
avg retr time: 0.0 ms avg retr time: 0.0 ms
sdv retr time: 0.0 ms sdv retr time: 0.0ms
Thanks,
Jerry
-John
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