Andrew Gallatin wrote: >Garrett D'Amore writes: > > The problem here is that the only reason to lower the MTU is to deal > > with cases where Path MTU discovery fails. For example, lowering the > > MTU because your upstream provider doesn't properly deal with frames > > larger than a PPP size or somesuch. > > > > Its frustrating that these cases still exist, but they do. In general, > > I agree, that lowering the MTU should not be necessary. And indeed, > > frankly nobody should need to touch the values provided by the media > > drivers when everything works properly. > >You may want to touch the values in order to reduce memory useage if >you know you cannot use jubmo frames. Since most drivers manage their >own receive buffers, this can add up. For example, my 10GbE driver, >depending on load, may allocate up to a (tunable) maximum of 4096 >receive buffers. The difference between 4096 1500b and 9000b frames >is nearly 30MB. > >It would be nice if the driver could be notified that the MTU is >changing so that it can re-allocate appropriately sized receive >buffers. Every other *nix that I've worked with does this. > >
It would be nice if the buffer space used by a driver could be specified in terms of MB rather than n buffers. Darren
