Re: sendfile+zerocopy: fairly sexy (nothing to do with ECN)

[Trond Myklebust <trond.myklebust@xxxxxxxxxx>]

>>>>> " " == Andrew Morton <andrewm@xxxxxxxxxx> writes:


     > Much the same story.  Big increase in sendfile() efficiency,
     > small drop in send() and NFS unchanged.

This is normal. The server doesn't do zero copy reads, but instead
copies from the page cache into an NFS-specific buffer using
file.f_op->read(). Alexey and Dave's changes are therefore unlikely to
register on NFS performance (other than on CPU use as has been
mentioned before) until we implement a sendfile-like scheme for knfsd
over TCP.
I've been wanting to start doing that (and also to finish the client
conversion to use the TCP zero-copy), but I'm pretty pressed for time
at the moment.

Cheers,
  Trond