From: "Catalin(ux) M. BOIE" <redacted>
Date: Thu, 27 Nov 2008 00:05:50 -0700 (MST)

Do you mean that it should be computed based on memory size or you mean
that it should be changeable on-the-fly, even when we have some
connections in the tables already?

I mean the latter.  We do this in other subsystems, such as
IPSEC, for various hashes.

Do you have some hints (where to look for a similar thing)?
The thing that worries me a little is the locking around the move and
maybe the latency involved. Yes, of course you will not change it several
times per minute, but...

You only increase, never decrease.

A lock is held during every access to these hash tables, so
the locking should be very similar.

Have a look at xfrm_hash_resize() in net/xfrm/xfrm_state.c to get
a good idea on how this stuff can be done.  And hey, that code
resizes 3 tables at once, you only need to handle one :)