Re: maximum data rates

["Paul Hyder" <Paul.Hyder --at-- noaa.gov>]

For Linux the PSC url plus http://www.csm.ornl.gov/~dunigan/netperf/netlinks.html are good.
Sounds like you have already seen web100.  Dunigan's list will get you to most of the
volumes of detail.  Info on what I use below.  YMMV (See also the message about CPU from Les.
A faster client host would help.)
	Paul Hyder

My collection of GigE tuning settings for Linux:
    1.  Make absolutely sure that your GigE device driver has interrupt aggregation enabled.
        (Should be default in recent kernels and drivers.)
    2.  Add memory if needed to match buffer sizes selected below.
    3.  Tune buffers (add to /etc/sysctl.conf and run "sysctl -p OR set manually in /proc/sys)
	Test and optimize for your needs, my hosts use:
	    net.core.rmem_max = 16777216
            net.core.wmem_max = 16777216
            net.core.rmem_default = 5242880
            net.core.wmem_default = 5242880
            net.ipv4.tcp_rmem = 262144 5242880 16777216
            net.ipv4.tcp_wmem = 262144 5242880 16777216
            net.core.netdev_max_backlog=2500
	NOTE: For back to back these mem values are too big, I'm expecting a RTT of up to ~100ms.
              Adjust at least the defaults to fit your expected bandwidth delay product.
	      (In most cases the defaults are too small for even back to back GigE.)
     4. Explicitly ifconfig the GigE interfaces:
	    ifconfig eth? txqueuelen 10000 mtu 8192

	The 8k jumbo frame works better for me than 9000.  Jumbo frames really helped my
	"in the building" throughput but if you can only handle 1500 leave the mtu off.

     5.  Test iperf using various combinations of the -w and -l commands!


Jason wrote:
> during testing, for client: the cpu is pentium II 266 MHz with redhat9 & for server: the cpu is pentium 4 2GHz with redhat 7.3. I can change both client & server to pentium 4 cpu while the type of OS is not important to me, as long as the combination can generate max data rate possible.
>
> Paul Hyder <Paul.Hyder --at-- noaa.gov> wrote:Would need to know which operating system and the CPU speed of the "...two PCs." to
> help much.
>
> It is indeed not difficult to get single flows to over 90% of a GigE but you probably
> need to tune buffers a bit. (e.g. On a dual 2.0GHz Opteron hardware with Linux.) If
> you run Linux I can provide details of what to modify. For Windows and others see the
> PSC url below.
> Paul Hyder
> NOAA Forecast Systems Lab
>
> Synopsis:
> General TCP tuning: http://www.psc.edu/networking/projects/tcptune/
> Internet2 iperf/bwctl TCP Throughput: http://abilene.internet2.edu/ami/bwctl_status.cgi/TCP/now
>
> Jason wrote:
>
> > I can only manage to achieve 229Mbps on 1Gbps link using a gigabit hub in between two PCs. Any idea to increase the volume of traffic?
> >
> > "Cottrell, Les" wrote:You can get around 960Mbps with iperf on a back to back 1Gbps link between two PCs. On a 10Gbps link one can get about 7.5Gbps, the limitation is the PCI-X bus.
> >
> >
> > ---------------------------------
> > From: owner-iperf-users --at-- dast.nlanr.net [mailto:owner-iperf-users --at-- dast.nlanr.net] On Behalf Of Jason
> > Sent: Tuesday, May 24, 2005 12:09 AM
> > To: Iperf Users
> > Subject: maximum data rates
> >
> >
> >
> > Dear all,
> >
> > I try iperf on 100 Mbps link & it is able to generate tcp traffic up to 97 Mbps. Any one try on Gigabit link & what is the maximum data traffic it can generate? Also, any one using web100 with iperf, because I think Iperf alone can generate near 100 Mbps & I am not too sure what web100 uses are.
> >
> > Thanks
> >
> >
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