On 9/5/2012 3:48 PM, Atchley, Scott wrote:
On Sep 5, 2012, at 3:06 PM, Christoph Lameter wrote:
On Wed, 5 Sep 2012, Atchley, Scott wrote:
AFAICT the network stack is useful up to 1Gbps and
after that more and more band-aid comes into play.
Hmm, many 10G Ethernet NICs can reach line rate. I have not yet tested any 40G
Ethernet NICs, but I hope that they will get close to line rate. If not, what
is the point? ;-)
Oh yes they can under restricted circumstances. Large packets, multiple
cores etc. With the band-aids….
With Myricom 10G NICs, for example, you just need one core and it can do line
rate with 1500 byte MTU. Do you count the stateless offloads as band-aids? Or
something else?
I have not tested any 40G NICs yet, but I imagine that one core will not be
enough.
Since you are using netperf, you might also considering experimenting
with the TCP_SENDFILE test. Using sendfile/splice calls can have a
significant impact for sockets-based apps.
Using 40G NICs (Mellanox ConnectX-3 EN), I've seen our applications hit
22Gb/s single core/stream while fully CPU bound. With sendfile/splice,
there is no issue saturating a 40G link with about 40-50% core
utilization. That being said, binding to the right core/node, message
size and memory alignment, interrupt handling, and proper host/NIC
tuning all have an impact on the performance. The state of
high-performance networking is certainly not plug-and-play.
- ezra
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