Andi Kleen wrote:
I'm personally not a big fan of TSO or TOE. They both add a lot of complexity
to the network stack, and have other downsides. The *best* way to solve
these problems is to engineer technologies to use larger packet sizes. Even
at 9k (or better yet 16k) the advantages of these offload schemes is
vanishingly small. (Though if a TOE can do zero-copy receive, this is a win
over what currently exists, but I think there are other ways to do that as
well.) The Linux kernel may not be able to do too much to encourage
deployment of larger MTUs, but NIC vendors probably can.
Hmm - but is a 9k or 16k packet on the wire not equivalent to a micro burst?
(actually it is not that micro compared to 1.5k packets). At least against
burstiness they don't help and make things even worse because the bursts
cannot be split up anymore.
Right. The other issue with jumbos frames (9000MTU) is that
the allocation needed is just over 2 pages for 4K page size
machines (common case). 3 page contig allocations tend to fail
once a server is heavily loaded and memory gets fragmented.
thanks,
Nivedita
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