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
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