Terrible NFS performance under 9.2-RELEASE?

[wollman at freebsd.org]

In article
<278396201.16318356.1390701347722.JavaMail.root at uoguelph.ca>, Rick
Macklem writes:

>Well, when I get home in April, I'll try the fairly recent Linux client
>I have at home and see what it does. Not sure what trick they could use
>to avoid the read before write for partial pages. (I suppose I can
>look at their sources, but that could be pretty scary;-)

For what it's worth, our performance for large-block 100%-read
workloads is also not what it could (or ought to) be.  Between two
20G-attached servers, I can get about 12 Gbit/s with three parallel
TCP connections.  (Multiple connections are required to trick the lagg
hash into balancing the load across both 10G links, because the hash
function used for load-balancing uses the source and destination
ports.)  On the same pair of servers, "dd if=/mnt/test bs=1024k" runs
at about 3 Gbit/s, whereas reading from the local filesystem goes
anywhere from 1.5 to 3 G*byte*/s (i.e., eight times faster) with much
higher CPU utilization.  Luckily, most of our users are only connected
at 1G so they don't notice.

I'm going to lose my test server soon (it has to go into production
shortly), so I'm not really able to work on this.  I'll have another
test server soon (old hardware being replaced by the new server) and
hope to be able to try out the new code that's going to be in 10.1,
with the expectation of upgrading to 10.x over summer break.

-GAWollman