[Beowulf] Performance tuning for Jumbo Frames
rpnabar at gmail.com
Mon Dec 14 11:35:14 PST 2009
On Sat, Dec 12, 2009 at 10:40 AM, Patrick Geoffray <patrick at myri.com> wrote:
> Most 10GE NIC have no problems reaching line rate at 1500 Bytes (the
> standard Ethernet MTU), the problem is the host OS stack (mainly TCP) where
> the per-packet overhead is important. One trick that all 10GE NICs worth
> their salt are doing these days is to fake a large MTU at the OS level,
> while keeping the wire MTU at 1500 Bytes (for compatibility). This is called
> TSO (Transmit Send Offload) and LRO (Large Receive Offload). The OS stack is
> using a virtual MTU of 64K and the NIC does segmentation/reassembly in
> hardware, sort of.
The TSO and LRO are only relevant to TCP though, aren't they? I am
using RDMA so that shouldn't matter. Maybe I am wrong.
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