James Carlson wrote: >> I'm personally a fan of having a minimal number of instructions in the >> data paths and the M_MULTIDATA code doesn't satisfy that - it needs to >> manage all the metadata which is extra work compared to a soft LSO >> implementation. >> >> So while LSO has some limitations, it is a more tractable way to >> amortize DMA/IOMMU overhead than MDT. > > LSO looks to the rest of the software like a middlebox in the network, > and that buys with it all of the technology change problems as we've > had in the past. Every time you make a transport change, you've got > to modify that middlebox to do something appropriate with that > transport bit, and that costs extra. Or you end up with "orphan" > protocols (like IPsec, SCTP, or IPv6) that just aren't supported and > always run in the slow path. Both answers are bad. Not really. LSO only happen on the tx server, and it's invisible to any other network parts. For the host, it's easy to decide whether to do LSO for the next transmission according to the current state of transport. It's actually "part" of transport protocol, but not a "middlebox" somewhere.
Look at hardware checksum offloading. It didn't start with wide coverage as it does today, but it has been proved very helpful to the performance. Even today, you have to disable some type of hardware checksum offloading when IPSec is present. Should we discuss whether to keep the hardware checksum offloading support in Solaris stack? By the way, LSO has its targeting area, and it's won full-TOE because of its simpleness for both software and hardware supports. Thanks, Roamer > > Simply accumulating writes avoids those problems, and that's what I > think is slightly attractive about MDT. Not that I'm wild about MDT, > given the overhead. > > For what it's worth, I think optimizing the path down into (and back > from) the driver is a better long-term solution. It doesn't require > things MDT. And it'll work for everybody, unlike LSO. > -- # telnet (650)-786-6759 (x86759) Connected to Solaris.Sun.COM. login: Lu, Yunsong Last login: January 2, 2007 from beyond.sfbay [EMAIL PROTECTED] v1.04 Since Mon Dec. 22, 2003 [EMAIL PROTECTED] Networking]# cd .. _______________________________________________ networking-discuss mailing list [email protected]
