On Wed, 2008-01-30 at 09:29 +0100, Bart Van Assche wrote:
I'd certainly say that's a totally unsupported conclusion.
Just because Solaris takes a particular design decision doesn't
automatically make it the right course of action.
Microsoft once pulled huge gobs of the C library and their windowing
system into the kernel in the name of efficiency. It proved not only to
be less efficient, but also to degrade their security model.
Deciding what lives in userspace and what should be in the kernel lies
at the very heart of architectural decisions. However, the argument
that "it should be in the kernel because that would make it faster" is
pretty much a discredited one. To prevail on that argument, you have to
demonstrate that there's no way to enable user space to do the same
thing at the same speed. Further, it was the same argument used the
last time around when the STGT vs SCST investigation was done. Your own
results on non-IB networks show that both architectures perform at the
same speed. That tends to support the conclusion that there's something
specific about IB that needs to be tweaked or improved for STGT to get
it to perform correctly.
Furthermore, if you have already decided before testing that SCST is
right and that STGT is wrong based on the architectures, it isn't
exactly going to increase my confidence in your measurement methodology
claiming to show this, now is it?
These are both features being independently worked on, are they not?
Even if they weren't, the combination of the size of SCST in kernel plus
the problem of having to find a migration path for the current STGT
users still looks to me to involve the greater amount of work.
James
--
