Hi Marc, According to iperf's doc: -w, --window #[KM] ... For UDP it is just the buffer which datagrams are received in, and so limits the largest receivable datagram size.
My current UDP buffer size is 109kB, and I am using 1470 byte packets; should be good enough ? But thanks for the tip, I'll try to increase it and see what happens. In the meantime I have found the CPU patch of Ingo Molnar for iperf "00_Iperf_Fix-CPU-Usage.diff", and applied it to iperf-2.0.4: I see quite an improvement in the now possible UDP sending rate: Losing less than 10 packets, it jumped fro 40MBit/s to 70 MBit/s for dual mode; and from 70MBit/s to 90Mbit/s for single mode. So at least the UDP perfomance looks like the TCP performance I get out of this hardware. Regs, Thomi Am Dienstag, 14. April 2009 01.41:40 schrieben Sie: > Hi, > > Try different values for the socket buffer size, especially on the > sender side. The option is wrongly called "window size". > > Cheers, > > Marc > > 2009/4/13 Thomi Schmid <[email protected]>: > > Hi, > > > > I am testing different ethernet switches regarding their ethernet frame > > dropping behaviour using iperf UDP mode (unicast and multicast). > > To do this I wanted to establish a baseline between the test PCs to make > > sure the sent packets do not get lost at the PCs, ie all losses are the > > switches problem. I am using iperf 2.0.4. I tested the iperf UDP setup > > using a crossover ethernet cable to connect the test PCs. > > > > Problem #1: iperf is not sending at the specified speed > > I specify "-b 100M" at the UDP client, but according to the client's > > reports I only get between 70..80Mbit/s. I can increase the > > "-b"-parameter to "200", which then gets me a higher reported throughput, > > but then also the UDP packet loss increases. > > > > Problem #2: iperf is loosing packets even with test PCs directly > > connected Using "-b 80M" or higher, I always get lost packets. The number > > of lost packets varies with the specified bandwidth setting "-b"; ie more > > requested bandwidth produces more lost packets. I have shutdown all(most) > > unnecessary services (like X11, SSHd, NFS etc) and ran iperf from > > console. > > > > The PCs are not new (from Celeron III/400MHz to Celeron M/1GHz) or low > > power (Intel Atom), the NICs are either Intel (e100) / Realtek (8139too) > > Fast Ethernet. All PCs are running current Linux kernels (2.6.27.x) and > > Ubuntu or openSuSE 11.1 installations. > > > > I was reading through the threads "Iperf Transmit leading to 100% CPU > > Utilization" and wondered if this problem, together with my rather low > > power hardware could be the cause of my above problems #1 and #2. The > > thread talks about patches to apply to iperf to improve the UDP mode, but > > I could neither find the patch itself or if it is applied to the iperf > > trunk source. > > > > Any help or comment on how to get rid or circumvent the above mentioned > > problems is appreciated. > > > > Regards, > > Thomi > > > > > > > > > > > > > > ------------------------------------------------------------------------- > >----- This SF.net email is sponsored by: > > High Quality Requirements in a Collaborative Environment. > > Download a free trial of Rational Requirements Composer Now! > > http://p.sf.net/sfu/www-ibm-com > > _______________________________________________ > > Iperf-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/iperf-users ------------------------------------------------------------------------------ This SF.net email is sponsored by: High Quality Requirements in a Collaborative Environment. Download a free trial of Rational Requirements Composer Now! http://p.sf.net/sfu/www-ibm-com _______________________________________________ Iperf-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/iperf-users
