Namecache lock contention?

[Ivan Voras]

I have this situation on a PHP server:

36623 www         1  76    0   237M 30600K *Name   6   0:14 47.27% php-cgi
36638 www         1  76    0   237M 30600K *Name   3   0:14 46.97% php-cgi
36628 www         1 105    0   237M 30600K *Name   2   0:14 46.88% php-cgi
36627 www         1 105    0   237M 30600K *Name   0   0:14 46.78% php-cgi
36639 www         1 105    0   237M 30600K *Name   5   0:14 46.58% php-cgi
36643 www         1 105    0   237M 30600K *Name   7   0:14 46.39% php-cgi
36629 www         1  76    0   237M 30600K *Name   1   0:14 46.39% php-cgi
36642 www         1 105    0   237M 30600K *Name   2   0:14 46.39% php-cgi
36626 www         1 105    0   237M 30600K *Name   5   0:14 46.19% php-cgi
36654 www         1 105    0   237M 30600K *Name   7   0:13 46.19% php-cgi
36645 www         1 105    0   237M 30600K *Name   1   0:14 45.75% php-cgi
36625 www         1 105    0   237M 30600K *Name   0   0:14 45.56% php-cgi
36624 www         1 105    0   237M 30600K *Name   6   0:14 45.56% php-cgi
36630 www         1  76    0   237M 30600K *Name   7   0:14 45.17% php-cgi
36631 www         1 105    0   237M 30600K RUN     4   0:14 45.17% php-cgi
36636 www         1 105    0   237M 30600K *Name   3   0:14 44.87% php-cgi

It looks like periodically most or all of the php-cgi processes are 
blocked in "*Name" for long enough that "top" notices, then continue, 
probably in a "thundering herd" way. From grepping inside /sys the most 
likely suspect seems to be something in the namecache, but I can't find 
exactly a symbol named "Name" or string beginning with "Name" that would 
be connected to a lock.

Has anyone investigated this before? Any ideas where to look?

The PHP script used above should not do any filesystem writing but it 
stats and reads a lot of small files and libraries.

This is 8-stable, UFS.