is vfs.lookup_shared unsafe in 7.3?

[cronfy]

Hello,

Trying to overtake high server load (sudden peaks of 15%us/85%sy, LA >
40, very slow lstat() at these moments, looks like some kind of lock
contention) I enabled vfs.lookup_shared=1 on two servers today. One is
FreeBSD-7.3 kernel csup'ed and built Sep  9 2010 and other is
FreeBSD-7.3 csup'ed and built Jul 16 2010.

The server with more fresh kernel is running nice and does not show
high load anymore. But on the second server it did not help. More,
after a few hours of work with vfs.lookup_shared=1 I noticed processes
stucked in "ufs" state. I tried to kill them with no luck. Disabling
vfs.lookup_shared freezed the whole system.

So, is vfs.lookup_shared=1 unsafe in 7.3? Did it become more stable
between 16 Jul and 9 Sep (is it the reason why first system is still
running?), or should I expect that it will freeze in a near time too?

Thanks in advance!

-- 
// cronfy