The need for a special SMB receive system call

[Andrew Theurer]

> Every system call I can eliminate, or push into the kernel (as in the
> fstat call in the sendfile code) means more CPU for yet another client and
> gets us closer to handling 10,000 clients :-)

FYI, my top three functions running netbench on linux are:

  8867 total                                      0.0044
   700 default_idle                              13.4615
   689 __generic_copy_to_user                    11.4833
   419 generic_file_write                         0.2272

This would seem to support your theory.  Sendfile/zerocopy got me an easy 20% 
improvement on netbench, and I would expect similar but slightly lower 
improvement for recvfile (I think netbench has a little more reads than 
writes).  

-Andrew Theurer