ndt-users list created

[Rich Carlson <>]

Justin;

The Web100 system uses 32bit counters, so I suspect the negative speeds 
come from the use of signed int vars instead of unsigned.

When testing on the local box, the traffic goes through the loopback 
interface (lo0) instead of the NIC.  This means you are testing the OS 
and it's memory management system more that anything else. 
Changing/setting variables on the ethx interface will have no effect.

You should not set the tcp_mem value to 16 M.  The value for this 
variable is in pages, NOT bytes.  See 
Documentation/networking/ip-sysctl.txt doc in the kernel source tree for 
more details.

tcp_mem - vector of 3 INTEGERs: min, pressure, max
        min: below this number of pages TCP is not bothered about its
        memory appetite.

        pressure: when amount of memory allocated by TCP exceeds this 
number
        of pages, TCP moderates its memory consumption and enters memory
        pressure mode, which is exited when memory consumption falls
        under "min".

        max: number of pages allowed for queueing by all TCP sockets.

        Defaults are calculated at boot time from amount of available
        memory.


Are you using the command line client (web100clt) or the Java Applet 
(via the browser) to run these tests?  It was recently reported that a 
site was getting high variability in the S2C tests with the Java client. 
 It turned out that they had 2 Java consoles installed.  Removing the 
older console cleared up the problem.

Regards;
Rich

On 9/27/2010 6:49 PM, Hao, Justin C wrote:
> So i'm setting up a pair of ndt test servers for our new datacenter and 
> running into some hurdles.
>
> First off, i haven't connected them to each other (or to a 10Gig network), so 
> all my testing has been on a single box running loopback tests to itself (i 
> have no other 10GigE hosts available to me at the moment).
>
> I'm running CentOS 5.5 and patched kernel 2.6.35 with the proper web100 
> version etc.
>
> It's currently hooked up via 1GigE and i've run several different clients 
> against it and I get good results for 1Gig performance
>
> I'm running loopback tests to tweak TCP settings while I wait for our 10Gig 
> environment to be made ready. I'm getting 15-18Gig/s for C2S but for S2C i'm 
> getting numbers all over the place. from 3.5Gig/s to 500Mb/s.  and most 
> particularly odd, i'm seeing negative numbers in some of the test output.
>
> I welcome any comments and suggestions for tuning this server (it's a dell 
> r610 w/ an intel 10GigE adapter)
>
> note: I've also configured the ethernet interface to use 9000 MTU and a 
> txqueuelen of 10000
>
> Server TCP settings:
>
> # increase TCP max buffer size setable using setsockopt()
>
> net.core.rmem_max = 16777216
> net.core.wmem_max = 16777216
>
> # increase Linux autotuning TCP buffer limits
> # min, default, and max number of bytes to use
> # set max to 16MB for 1GE, and 32M or 54M for 10GE
>
> net.ipv4.tcp_mem = 16777216 16777216 16777216
> net.ipv4.tcp_rmem = 10240 87380 16777216
> net.ipv4.tcp_wmem = 10240 65536 16777216
>
> net.ipv4.tcp_window_scaling = 1
>
> # don't cache ssthresh from previous connection
> net.ipv4.tcp_no_metrics_save = 1
>
> # recommended to increase this for 10G NICS
> net.core.netdev_max_backlog = 262144
>
> NDT Output:
>
> TCP/Web100 Network Diagnostic Tool v3.6.3
> Click START to start the test
>
> ** Starting test 1 of 1 **
> Connecting to '127.0.0.1' [/127.0.0.1] to run test
> Connected to: 127.0.0.1--  Using IPv4 address
> Checking for Middleboxes  . . . . . . . . . . . . . . . . . .  Done.
> Checking for firewalls . . . . . . . . . . . . . . . . . . .  Done.
> running 10s outbound test (client-to-server [C2S]) . . . . . 13744.22Mb/s
> running 10s inbound test (server-to-client [S2C]) . . . . . . -83702.57kb/s
> Server unable to determine bottleneck link type.
>   [S2C]: Packet queueing detected
>
> Click START to re-test
>
> ** Starting test 1 of 1 **
> Connecting to '127.0.0.1' [/127.0.0.1] to run test
> Connected to: 127.0.0.1--  Using IPv4 address
> Checking for Middleboxes  . . . . . . . . . . . . . . . . . .  Done.
> Checking for firewalls . . . . . . . . . . . . . . . . . . .  Done.
> running 10s outbound test (client-to-server [C2S]) . . . . . 12876.05Mb/s
> running 10s inbound test (server-to-client [S2C]) . . . . . . 1006.86Mb/s
> Server unable to determine bottleneck link type.
>   [S2C]: Packet queueing detected
>
> Click START to re-test
>
> ** Starting test 1 of 1 **
> Connecting to '127.0.0.1' [/127.0.0.1] to run test
> Connected to: 127.0.0.1--  Using IPv4 address
> Checking for Middleboxes  . . . . . . . . . . . . . . . . . .  Done.
> Checking for firewalls . . . . . . . . . . . . . . . . . . .  Done.
> running 10s outbound test (client-to-server [C2S]) . . . . . 18466.0Mb/s
> running 10s inbound test (server-to-client [S2C]) . . . . . . -1710004.63kb/s
> Server unable to determine bottleneck link type.
>   [S2C]: Packet queueing detected
>
> Click START to re-test
>
>
> -----
> Justin Hao
> CCNA
> Network Engineer, ITS Networking
> The University of Texas at Austin
>
> -----