Hi everybody,

Just like a few other people over the last year, I've observed that NFS 
over UDP with a 2.6 client is a lot slower than it used to be in 2.4.x 
times.  Previous discussions as for instance 
http://www.ussg.iu.edu/hypermail/linux/kernel/0405.3/0866.html, have 
concluded that this is due to mixed Gigabit/100Mbit networks.  I've 
successfully traced the crucial change to a change between kernel 2.4.22 
and 2.4.23.  On an identical Red Hat 7.3 machine, I get five to ten 
times slower performance on 2.4.23 than on 2.4.22.

I have isolated part of the patch, applied it by hand to 2.6.8 sources, 
and compiled a working 2.6.8 kernel that has eight to ten times higher 
performance on a simple NFS read operation than one without my patch. 
The patch is included for comment.  (I'm only just subscribing to the 
list, so please CC: me on replies.)

Note that the patch is against Debian's kernel-source-2.6.8 package 
which does not contain pristine sources; as far as I can tell, the 
relevant code in Debian is not different from mainstream kernel though.

I would like some feedback whether someone is aware of this problem.  I 
don't understand what the code change in 2.4.23 was supposed to achieve; 
I'm essentially backing out that change and have not observed any 
difference apart from a 8x speedup.  What should I be looking for?

Alex

-- 
Alexander Jolk         /         BUF Compagnie
tel +33-1 42 68 18 28 /  fax +33-1 42 68 18 29