Re: Open-FCoE on linux-scsi

[Vladislav Bolkhovitin <vst@vlnb.net>]

FUJITA Tomonori wrote:
>>Thus, I believe, that partial user space, partial kernel space approach 
>>for building SCSI targets is the move in the wrong direction, because it 
>>brings practically nothing, but costs a lot.
> 
> We have not discussed such topic. FCoE target can be implemented fully
> in user space if I understand correctly.

Really? FCoE target doesn't need an FC hardware target? And FCoE isn't 
sensitive to the packets forwarding latency?

For fully in-kernel approach it is possible to make the packets 
forwarding zero-copy in both directions FC<->Ethernet, which is 
practically impossible with user space. Modern memory has few GB/s 
throughput, so guess how much latency data copying will add on 10Gbps 
speed. Thus, I believe, if performance matters, FCoE should be in 
kernel, at least hot processing path, when management possibly done in 
user space as for open-iscsi. But user space/kernel separation should 
only be done if the additional user space/kernel interface won't 
complicate things too much.

Vlad