Bob,
I tried with different qdisc transmit buffer sizes from 2000 packets
to 0 packets, but at least on my machine this did not affect the
performance.. For example Iperf client output if qdisc Tx buffer
length is one packet:
root@3:~# ip link show dev eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP
mode DEFAULT qlen 1
link/ether 00:1d:09:f0:92:ab brd ff:ff:ff:ff:ff:ff
root@3:~# iperf -c 192.0.2.1 -fm -t 10 -u -b 800m
------------------------------------------------------------
Client connecting to 192.0.2.1, UDP port 5001
Sending 1470 byte datagrams
UDP buffer size: 0.22 MByte (default)
------------------------------------------------------------
[ 3] local 90.191.152.226 port 43454 connected with 192.0.2.1 port 5001
[ ID] Interval Transfer Bandwidth
[ 3] 0.0-10.0 sec 966 MBytes 810 Mbits/sec
[ 3] Sent 688942 datagrams
[ 3] WARNING: did not receive ack of last datagram after 10 tries.
root@3:~#
> For me, with traffic control and the txqueuelen set to zero, the iperf client
> does not seem to get the ENOBUFS and the tx rate reporting is that per the -b
> (offered load).
Same for me.
Has anyone managed to reproduce the behavior described in my initial
e-mail with decreasing the Tx buffers sizes on (virtual-)machine where
the Iperf client is running?
regards,
Martin
On Fri, Sep 26, 2014 at 7:08 AM, Bob (Robert) McMahon
<rmcma...@broadcom.com> wrote:
> Hi Martin,
>
> For me, with traffic control and the txqueuelen set to zero, the iperf client
> does not seem to get the ENOBUFS and the tx rate reporting is that per the -b
> (offered load). The iperf server is receiving at the qdisc setting (shaped
> rate) vs the offered load (-b). So it does look like there is some interplay
> between ENOBUFS, qdiscs, and the txqueuelen that affects tx rate reporting.
>
> Bob
> -----Original Message-----
> From: Martin T [mailto:m4rtn...@gmail.com]
> Sent: Thursday, September 25, 2014 4:10 PM
> To: Bob (Robert) McMahon
> Cc: Marc Herbert; Andrew Gallatin; iperf-users@lists.sourceforge.net
> Subject: Re: [Iperf-users] Iperf client sends out less UDP traffic than
> determined with "-b" flag
>
> Bob,
>
> I see, thanks!
>
>
> As a last thing, I played around with qdisc buffer and kernel NIC
> driver circular-buffer size. Unfortunately I wasn't able to reproduce
> the results I saw on this virtual-machine. Even with no qdisc
> buffer("ip link set dev eth0 txqueuelen 0") and lowest NIC driver
> buffer supported on my tg3(ver 3.2.0-4-amd64) driver for my Broadcom
> BCM5721 chipset, the Iperf client sent out as much UDP traffic as
> determined with "-b" option:
>
>
> root@3:~# ip link show dev eth0
> 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP
> mode DEFAULT
> link/ether 00:1d:09:f0:92:ab brd ff:ff:ff:ff:ff:ff
> root@3:~# ethtool -g eth0
> Ring parameters for eth0:
> Pre-set maximums:
> RX: 511
> RX Mini: 0
> RX Jumbo: 0
> TX: 511
> Current hardware settings:
> RX: 0
> RX Mini: 0
> RX Jumbo: 0
> TX: 55
>
> root@3:~# iperf -c 192.0.2.1 -fm -t 10 -u -b 800m
> ------------------------------------------------------------
> Client connecting to 192.0.2.1, UDP port 5001
> Sending 1470 byte datagrams
> UDP buffer size: 0.22 MByte (default)
> ------------------------------------------------------------
> [ 3] local 192.168.1.45 port 44172 connected with 192.0.2.1 port 5001
> [ ID] Interval Transfer Bandwidth
> [ 3] 0.0-10.0 sec 962 MBytes 807 Mbits/sec
> [ 3] Sent 686293 datagrams
> [ 3] WARNING: did not receive ack of last datagram after 10 tries.
> root@3:~#
>
>
> Has anyone managed to reproduce the behavior described in my initial
> e-mail with decreasing the Tx buffers sizes on (virtual-)machine where
> the Iperf client is running?
>
>
> regards,
> Martin
>
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