> I wonder if the switch could be implicated. We have seen some (cheap) > GbE switches not support (in practice) jumbo frames (irrespective of > literature).
I got the SMC 8624T because it advertised both Jumbo and link aggregation. Is this one of the "cheap" you have seen that does not work with Jumbo? paulo > Nifty Tom Mitchell wrote: >> On Sat, Jan 24, 2009 at 09:36:09AM -0600, Gerry Creager wrote: >>> Couple of follow-up notes. >>> >>> MTU=4500: Had one node fall over with the same overflow errors. >>> MTU=3000: A WRF model is running, but single timesteps are executing >>> 2.5x slower than MTU=1500 > > Segment offload? Is TSO on or off? > > ethtool -k eth0 > > will tell you. You might also have one very reluctant machine, in the > sense of being unwilling to switch their mtu. Could you do an > > ifconfig eth0 | grep MTU > > on each machine and verify that everyone is using the right MTU? > > >>> >>> I'll go snag the new driver and compile it. After all: What can it >>> hurt! >>> >>> Thanks, Guy! >>> >>> Regards, Gerry >>> >>> Guy Coates wrote: >>>> Hi, >>>> >>>> We have also seen problems with the bnx2 drivers. >>>> >>>> I got a more recent set of bnx2 drivers from Broadcom: >>>> >> ...... >> >> Has the data been snooped for this data to see if all >> is as expected. >> >> If you are seeing a natural MTU running faster than a jumbo MTU >> then something is fragmenting or causing fragmentation of the data. >> >> Should the MTU=4500 causes overflow errors it might be related to >> fragmentation. >> Both the sender and receiver have to keep all the bits on a reliable >> transfer until the data has been acknowledged. At one time >> fragmentation >> could only be done once to a minimum MTU in the life of a packet. >> >> In addition to snooping packets try "tracepath" to and from all >> the involved boxes to discover what is going on. >> >> > > > -- > Joseph Landman, Ph.D > Founder and CEO > Scalable Informatics LLC, > email: land...@scalableinformatics.com > web : http://www.scalableinformatics.com > http://jackrabbit.scalableinformatics.com > phone: +1 734 786 8423 x121 > fax : +1 866 888 3112 > cell : +1 734 612 4615 > _______________________________________________ > Beowulf mailing list, Beowulf@beowulf.org > To change your subscription (digest mode or unsubscribe) visit > http://www.beowulf.org/mailman/listinfo/beowulf > -- Paulo Afonso Lopes | Tel: +351- 21 294 8536 Departamento de Informática | 294 8300 ext.10763 Faculdade de Ciências e Tecnologia | Fax: +351- 21 294 8541 Universidade Nova de Lisboa | e-mail: p...@di.fct.unl.pt 2829-516 Caparica, PORTUGAL _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
