Terrible NFS performance under 9.2-RELEASE?

[J David]

On Fri, Jan 24, 2014 at 7:10 PM, Rick Macklem <rmacklem at uoguelph.ca> wrote:
> I would like to hear if you find Linux doing read before write when
> you use "-r 2k", since I think that is writing less than a page.

It doesn't.  As I reported in the original test, I used an 8k
rsize/wsize and a 4k write size on the Linux test and no
read-before-write was observed.  And just now I did as you asked, a 2k
test with Linux mounting with 32k rsize/wsize.  No extra reads,
excellent performance.  FreeBSD, with the same mount options, does
reads even on the appends in this case and can't.

                                                            random  random

              KB  reclen   write rewrite    read    reread    read   write

Linux    1048576       2  281082  358672                    125687  121964

FreeBSD  1048576       2   59042   22624                     10304
1933


For comparison, here's the same test with 32k reclen (again, both
Linux and FreeBSD using 32k rsize/wsize):

                                                            random  random

              KB  reclen   write rewrite    read    reread    read   write

Linux    1048576      32  319387  373021                    411106  364393

FreeBSD  1048576      32   74892   73703                     34889   66350


Unfortunately it sounds like this state of affairs isn't really going
to improve, at least in the near future.  If there was one area where
I never thought Linux would surpass us, it was NFS. :(

Thanks!