[ofa-general] Expected RDMA performance

[Peter Kjellstrom]

On Thursday 18 October 2007, Chuck Hartley wrote:
...
> 8388608        5000            1342.12               1342.12
> ------------------------------------------------------------------
>
> Is this typical RDMA performance?

It's close to what I've seen on similar hw. ~1400 is what you can push through 
the 8x pci-e of the intel 5000 chipset (confirmed by trying 4x pci-e which 
has shown ~700).

> What is the maximum theoretical BW for 
> DDR IB - 1525MB/sec?

No, it's 20 Gbps on the wire and 8/10 encoded so 16 Gbps effective which is 
2000 MB/s (10-base) and 1907 MiB/s (2-base).

On our system (with a different HCA) we see quite a difference with 
snoop-filter off (bios option). With snoop off (our) application performance 
goes up (not very suprising) but IB performance goes down (latency 0.4us 
worse and bw ~1400->1200).

/Peter
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