NFS client patch that implements a list of dirty byte ranges in a buffer

[Rick Macklem]

Hi,

I created this patch after the discussion by John Baldwin in late August under
the Subject: Fixes to allow write clustering of NFS writes from a FreeBSD NFS client

First off, I am in no way trying to "steal John's thunder" and I hope he will
continue pursuing the good work he's doing on the above.

However, I thought that the patch might be interesting to others
who like to live on the "bleeding edge" and use NFS for source tree
building, since the patch seems to help with the performance of that.
My simple test using a run of "make -j4 buildworld" without/with
the patch reduced the elapsed time from 4:17 to 2:42. (This was in no
way a benchmark and used very slow single core i386 hardware, but it
at least suggests that the patch may be useful.)

So, if anyone is interested in trying the patch, it is at:
  http://people.freebsd.org/~rmacklem/dirtybuflist.patch

But, be forewarned, this patch has been minimally tested and only on single
core i386 hardware.

If you do try the patch, please let me know how it goes, rick