Hi Adrian, On 4/29/07, Adrian Knoth <a...@drcomp.erfurt.thur.de> wrote:
On Sun, Apr 29, 2007 at 10:18:01AM -0400, George Bosilca wrote:
[snip]
BTW: How does multi TCP BTL works? I see num_links, but I wonder if kernel channel bonding would achieve the same results...
Unfortunately, kernel channel bonding is very unlikely to achieve the same results as Open MPI's striping with multi TCP BTL. Here is a relevant snippet of the documentation for kernel channel bonding: ======== balance-rr: This mode is the only mode that will permit a single TCP/IP connection to stripe traffic across multiple interfaces. It is therefore the only mode that will allow a single TCP/IP stream to utilize more than one interface's worth of throughput. This comes at a cost, however: the striping often results in peer systems receiving packets out of order, causing TCP/IP's congestion control system to kick in, often by retransmitting segments. ======== The Open MPI way avoids this packet reordering problem, since any individual TCP stream is carried by only a single NIC at either end of the transmission. Since Open MPI splits the MPI traffic across multiple TCP streams, additional throughput is possible without the low-level packet reordering problem. If you really want to know more about this, I could go on at length, but I'll spare the rest of the readers on the mailing list for now. -- Tim Mattox - http://homepage.mac.com/tmattox/ tmat...@gmail.com || timat...@open-mpi.org I'm a bright... http://www.the-brights.net/
